which are the two forces that are primarily responsible for propulsion in swimming
18567846
Ocyropsis is a genus of Ctenophores, which are commonly known as Comb Jellies. Ocyropsis belong to the family of Ocyropsidae. Ocyropsis possesses two large lateral muscular lobes and four auricles, and appear pale and translucent in color. Ocyropsis habitat is not precise as their gelatinous composition can make it difficult to study. They have been found in warm and cold waters. Unlike other, slow swimming Ctenophores, Ocyropsis are efficient in evading their predators. They use their oral lobes for additional propulsion and a secrete luminous mucous in efforts to evade predators. The muscular oral lobes of the Ocyropsis are used to grab its prey, and then moved to the prehensile mouth for absorption. Distribution Habitat There is lack of knowledge known about Ctenophores habitats. Ocyropsis have been found in both warm and cold waters. They were found and photographed specifically near South Africa near Southern Mozambique to False Bay. There have also been reports of Ocyropsis found near the Madeira Archipelago specifically near Port Santo. The two spotting occurred at 2m- 6m in depth. This sighting at Port Santo, has been the furthest North Atlantic Ocean sighting of an Ocyposis. Typically found in subtropical epielagic water along the Northeastern Pacific. Other sightings have included Southern California, Gulf of Mexico, Western Pacific, and the Indian Ocean. Movement Typically Ctenophores are slow swimmers that use cilia based propulsion to swim. Due to their slow movement, it puts them at a disadvantage to predators. Unlike the other Ctenophores, Ocyropsis have an advanced method of propulsion for swimming. They have broad oral lobes, typical used for feeding, that are used to row for extra propulsion. They use their broad oral lobes in addition with ciliary current for locomotion. Ocyropsis swimming speeds have been found to be double top speeds of other gelatinous species. They have been found to be more successful in invading predators at night than during the day. Once they are startled, they begin to use their jet propulsion and release a luminous mucous that causes confusion to predators as well. Eating habits Ocyropsis forage horizontally, and while they eat create a small wake. This wake is created from the intense compression of the organisms body and location of the ctene rows. The muscular oral lobes of the Ocyropsis are used to grab its prey, and then moved to the prehensile mouth for absorption. Morphology Ocyropsis shape is noted as looking like two hands together praying, and are pale and translucent in color. The shape consists of two large lateral muscular lobes and 4 auricles varying in size. The lateral lobes extend beyond the mouth no more than about 5 cm. Oftentimes the lobes will be found with pigmented spots of brown or black. The sub-tentacular ctene row is shorter in length than the sub-stomadeal ctene row. Specifically sub-tentacular ctene rows having 25-27 ctene plates compared to sub-stomdeal ctene rows having 35-37 ctene plates. Ctenophores are named after their cilia rows used in movement. A ctene row is enragement of cilia. As
Ocyropsis
2765047
Molecular motors are natural (biological) or artificial molecular machines that are the essential agents of movement in living organisms. In general terms, a motor is a device that consumes energy in one form and converts it into motion or mechanical work; for example, many protein-based molecular motors harness the chemical free energy released by the hydrolysis of ATP in order to perform mechanical work. In terms of energetic efficiency, this type of motor can be superior to currently available man-made motors. One important difference between molecular motors and macroscopic motors is that molecular motors operate in the thermal bath, an environment in which the fluctuations due to thermal noise are significant. Examples Some examples of biologically important molecular motors: Cytoskeletal motors Myosins are responsible for muscle contraction, intracellular cargo transport, and producing cellular tension. Kinesin moves cargo inside cells away from the nucleus along microtubules, in anterograde transport. Dynein produces the axonemal beating of cilia and flagella and also transports cargo along microtubules towards the cell nucleus, in retrograde transport. Polymerisation motors Actin polymerization generates forces and can be used for propulsion. ATP is used. Microtubule polymerization using GTP. Dynamin is responsible for the separation of clathrin buds from the plasma membrane. GTP is used. Rotary motors: FoF1-ATP synthase family of proteins convert the chemical energy in ATP to the electrochemical potential energy of a proton gradient across a membrane or the other way around. The catalysis of the chemical reaction and the movement of protons are coupled to each other via the mechanical rotation of parts of the complex. This is involved in ATP synthesis in the mitochondria and chloroplasts as well as in pumping of protons across the vacuolar membrane. The bacterial flagellum responsible for the swimming and tumbling of E. coli and other bacteria acts as a rigid propeller that is powered by a rotary motor. This motor is driven by the flow of protons across a membrane, possibly using a similar mechanism to that found in the Fo motor in ATP synthase. Nucleic acid motors: RNA polymerase transcribes RNA from a DNA template. DNA polymerase turns single-stranded DNA into double-stranded DNA. Helicases separate double strands of nucleic acids prior to transcription or replication. ATP is used. Topoisomerases reduce supercoiling of DNA in the cell. ATP is used. RSC and SWI/SNF complexes remodel chromatin in eukaryotic cells. ATP is used. SMC proteins responsible for chromosome condensation in eukaryotic cells. Viral DNA packaging motors inject viral genomic DNA into capsids as part of their replication cycle, packing it very tightly. Several models have been put forward to explain how the protein generates the force required to drive the DNA into the capsid. An alternative proposal is that, in contrast with all other biological motors, the force is not generated directly by the protein, but by the DNA itself. In this model, ATP hydrolysis is used to drive protein conformational changes that alternatively dehydrate and rehydrate the DNA, cyclically driving it from B-DNA to A-DNA and back again. A-DNA
Molecular motor
34725780
Platynereis dumerilii is a species of annelid polychaete worm. It was originally placed into the genus Nereis and later reassigned to the genus Platynereis. Platynereis dumerilii lives in coastal marine waters from temperate to tropical zones. It can be found in a wide range from the Azores, the Mediterranean, in the North Sea, the English Channel, and the Atlantic down to the Cape of Good Hope, in the Black Sea, the Red Sea, the Persian Gulf, the Sea of Japan, the Pacific, and the Kerguelen Islands. Platynereis dumerilii is today an important lab animal, it is considered as a living fossil, and it is used in many phylogenetic studies as a model organism. Description Platynereis dumerilii is a small marine ragworm: Males reach a length of 2 to 3 cm, while females reach a length of 3 to 4 cm. Like a number of invertebrate phyla, Platynereis dumerilii has an axochord, a paired longitudinal muscle that displays striking similarities to the notochord regarding position, developmental origin, and expression profile. Its early trochophore larva has a pair of the simplest eyes in the animal kingdom, each eye consists only of a photoreceptor cell and a pigment cell. Locomotion P. dumerilii worms have a ciliated surface which beats synchronously to drive locomotion and fluid flow. Larvae have segmental multiciliated cells that regularly display spontaneous coordinated ciliary arrests, which compose the ciliomotor circuitry in the worms. Whole-body coordination of ciliary locomotion is performed by a "stop-and-go pacemaker system". As the worms develop, they use chaetae, and then parapodia, for locomotion. Unlike other polychaetes, in Platynereis larvae, the parapodia are used only for navigation while the cilia are responsible for propulsive force. Senses Photoreceptor cells Platynereis dumerilii larvae possess two kinds of photoreceptor cells: Rhabdomeric and ciliary photoreceptor cells. The ciliary photoreceptor cells are located in the deep brain of the larva. They are not shaded by pigment and thus perceive non-directional light. The ciliary photoreceptor cells resemble molecularly and morphologically the rods and cones of the human eye. Additional, they express an ciliary opsin that is more similar to the visual ciliary opsins of vertebrate rods and cones than to the visual rhabdomeric opsins of invertebrates. Therefore, it is thought that the urbilaterian, the last common ancestor of mollusks, arthropods, and vertebrates already had ciliary photoreceptor cells. The ciliary opsin is UV-sensitive (λmax = 383 nm), and the ciliary photoreceptor cells react on non-directional UV-light by making the larvae swimming down. This forms a ratio-chromatic depth-gauge with phototaxis of the rhabdomeric photoreceptor cells of the eyes. A rhabdomeric photoreceptor cell forms with a pigment cell a simple eye. A pair of these eyes mediate phototaxis in the early Platynereis dumerilii trochophore larva. In the later nectochaete larva, phototaxis is mediated by the more complex adult eyes. The adult eyes express at least three opsins: Two rhabdomeric opsins and a Go-opsin. The three opsins there mediate phototaxis all the same way via depolarization, even so a scallop Go-opsin is known to hyperpolarize. Chemical P.
Platynereis dumerilii
19995454
Several organisms are capable of rolling locomotion. However, true wheels and propellers—despite their utility in human vehicles—do not play a significant role in the movement of living things (with the exception of certain flagella, which work like corkscrews). Biologists have offered several explanations for the apparent absence of biological wheels, and wheeled creatures have appeared often in speculative fiction. Given the ubiquity of wheels in human technology, and the existence of biological analogues of many other technologies (such as wings and lenses), the lack of wheels in nature has seemed, to many scientists, to demand explanation—and the phenomenon is broadly explained by two factors: first, there are several developmental and evolutionary obstacles to the advent of a wheel by natural selection, and secondly, wheels have several drawbacks relative to other means of propulsion (such as walking, running, or slithering) in natural environments, which would tend to preclude their evolution. This environment-specific disadvantage has also led humans in certain regions to abandon wheels at least once in history. Known instances of rotation in biology There exist two distinct modes of locomotion using rotation: first, simple rolling; and second, the use of wheels or propellers, which spin on an axle or shaft, relative to a fixed body. While many creatures employ the former mode, the latter is restricted to microscopic, single-celled organisms. Rolling Some organisms use rolling as a means of locomotion. These examples do not constitute the use of a wheel, as the organism rotates as a whole, rather than employing separate parts which rotate independently. Several species of elongate organisms form their bodies into a loop to roll, including certain caterpillars (which do so to escape danger), tiger beetle larvae, myriapods, mantis shrimp, Armadillidiidae, and Mount Lyell salamanders. Other species adopt more spherical postures, primarily to protect their bodies from predators; this posture has been seen in pangolins, wheel spiders, hedgehogs, armadillos, armadillo girdled lizards, isopods, and fossilized trilobites. Pangolins and wheel spiders have been observed to purposely roll away from predators. These species may roll passively (under the influence of gravity or wind) or actively, typically by altering their shape to generate a propulsive force. Tumbleweeds, which are the above-ground portions of certain plants, separate from their root structure and roll in the wind to distribute their seeds. These plants are found especially in open plain environments. The most well-known of these include Kali tragus (also known as Salsola tragus), or prickly Russian thistle, which arrived in North America in the late 19th century, and gained a reputation as a noxious weed. Fungi of the genus Bovista are known to use the same strategy to disperse their spores. Rotifers are a phylum of microscopic but multi-celled animals, typically found in freshwater environments. Although the Latin name rotifer means 'wheel-bearer', these organisms do not have any rotating structures, but rather a ring of rhythmically beating cilia used for feeding and propulsion. Keratinocytes, a type of skin cell, migrate with a rolling motion during the process of wound healing. These cells
Rotating locomotion in living systems
22641483
Fin and flipper locomotion occurs mostly in aquatic locomotion, and rarely in terrestrial locomotion. From the three common states of matter — gas, liquid and solid, these appendages are adapted for liquids, mostly fresh or saltwater and used in locomotion, steering and balancing of the body. Locomotion is important in order to escape predators, acquire food, find mates and bury for shelter, nest or food. Aquatic locomotion consists of swimming, whereas terrestrial locomotion encompasses walking, 'crutching', jumping, digging as well as covering. Some animals such as sea turtles and mudskippers use these two environments for different purposes, for example using the land for nesting, and the sea to hunt for food. Aquatic locomotion with fins and flippers Aquatic locomotion of fish Fish live in fresh or saltwater habitats and some exceptions are capable of coming on land (mudskippers). Most fish have muscles called myomeres, along each side of the body. To swim, they alternately contract one side and relax the other side in a progression which goes from the head to the tail. In this way, an undulatory locomotion results, first bending the body one way in a wave which travels down the body, and then back the other way, with the contracting and relaxing muscles switching roles. They use their fins to propel themselves through the water in this swimming motion. Actinopterygians, the ray-finned fish show an evolutionary pattern of fine control ability to control the dorsal and ventral lobe of the caudal fin. Through developmental changes, intrinsic caudal muscles were added, which enable fish to exhibit such complex maneuvers such as control during acceleration, braking and backing. Studies have shown that the muscles in the caudal fin, have independent activity patterns from the myotomal musculature. These results show specific kinematic roles for different part of the fish's musculature. A curious example of fish adaption is the ocean sunfish, also known as the Mola mola. These fish have undergone significant developmental changes reducing their spinal cord, giving them a disk like appearance, and investing in two very large fins for propulsion. This adaptation usually gives them the appearance that they are as long as they are tall. They are also amazing fish in that they hold the world record in weight gain from fry to adult (60 million times its weight). Aquatic locomotion of marine mammals Swimming mammals, such as whales, dolphins, and seals, use their flippers to move forward through the water column. During swimming sea lions have a thrust phase, which lasts about 60% of the full cycle, and the recovery phase lasts the remaining 40%. A full cycle duration lasts about 0.5 to 1.0 seconds. Changing direction is a very rapid maneuver that is initiated by head movement towards the back of the animal that is followed by a spiral turn with the body. Due to their pectoral flippers being so closely located to their center of gravity, sea lions are capable of displaying astounding maneuverability in the pitch, roll, and yaw direction and are therefore
Fin and flipper locomotion
156477
The Volkswagen Schwimmwagen (literally "swimming car") is a light four-wheel drive amphibious car, used extensively by German ground forces during the Second World War. With over 15,000 units built, the Schwimmwagen is the most-produced amphibious car in history. Prototyped as the Type 128, it entered full-scale production as the Type 166 in 1941 for the Wehrmacht – Nazi Germany's military. Development The Porsche / Volkswagen Schwimmwagen used the engine and mechanicals of the VW Type 86 four-wheel drive prototype of the Kübelwagen, also used for the Type 87 four-wheel drive 'Kübel/KDF' Command Car (Kommandeurswagen), which in turn were based on those of the civilian KDF-Wagen. Erwin Komenda, Ferdinand Porsche's first car-body designer, was forced to develop an all-new unitized bodytub structure, since the flat floorpan chassis of the existing VW vehicles was unsuited to smooth movement through water. Komenda patented his ideas for the swimming car at the German Patent office. The initial Schwimmwagen, Type 128 prototype, was based on the full-length Kübelwagen wheelbase of . Pre-production units of the 128, fitted with custom welded bodytubs, demonstrated that this construction was too weak for off-road use. It had insufficient torsional rigidity, and easily suffered hull-ruptures at the front cross-member, as well as in the wheel-wells. This was unacceptable for an amphibious vehicle. The large-scale production models (Type 166) had a reduced wheelbase of which resolved these issues. Schwimmwagens were produced by the Volkswagen factory at Fallersleben /Stadt des KdF-Wagens and Porsche's facilities in Stuttgart; with the bodies (or rather hulls) produced by Ambi Budd in Berlin. 15,584 Type 166 Schwimmwagen were produced from 1941 through 1944; 14,276 at Fallersleben and 1,308 by Porsche; the VW 166 is the most-produced amphibious car in history. Only 189 are known by the Schwimmwagen Registry to remain today, and only 13 have survived without restoration work. Technology All Schwimmwagens were four-wheel drive in first gear (and reverse gears on some models) only and had ZF self-locking differentials on the front and rear axles. As with the Kübelwagen, the Schwimmwagen had rear portal axles, which provided increased ground clearance, while at the same time reducing drive-line torque stresses with their gear reduction at the wheels. The Schwimmwagen had a top speed of 50 miles per hour (80 km/h) on land. When crossing a body of water a screw propeller could be lowered down from the rear deck/engine cover. When in place a simple coupling provided drive straight from an extension of the engine's crankshaft. This meant that screw propulsion always drove forward. The Schwimmwagen had a top speed of in the water. For reversing in the water there was the choice of using the standard equipment paddle or running the land drive in reverse, allowing the wheel-rotation to slowly take the vehicle back. The front wheels doubled up as rudders, so steering was done with the steering wheel both on land and on water. The Schwimmwagen could also be steered by the passengers using the paddle(s). Gallery See also Trippel SG6 - another German amphibious
Volkswagen Schwimmwagen
2468705
Miguel Rodríguez (born 1952) is the Chief of the Integration Office of the Cape Canaveral Spaceport Management Office. Early years Rodríguez was born in Santurce, Puerto Rico, a section of the city of San Juan, Puerto Rico where he received both his primary and secondary education. In 1969, he along with millions of other people around the world, witnessed the historical moment when Neil Armstrong from the Apollo mission stepped on the Moon's surface. Like so many other young men at the time, Rodríguez felt inspired to consider a career in the Space program of the United States known as NASA. After Rodríguez graduated from Colegio Espiritu Santo high school in Hato Rey, in 1971, he enrolled in the University of Puerto Rico at Mayagüez, where the Engineering College is located. Rodríguez earned his Mechanical Engineer Degree in 1976, however he had applied for a job with NASA in 1975, a year before his graduation. After graduating, he was called for an interview and offered a job in NASA. He became a mechanical engineer, designing parts for the Space Shuttle, at Marshall Space Flight Center in Huntsville, Alabama. Career in NASA In 1979, Rodríguez was transferred to the Kennedy Space Center in Florida where he was responsible for the activation and validation of facilities for processing Space Shuttle payloads and experiments. He rose through the engineering ranks and was promoted to the position of Payload Integration Engineer responsible for the STS-31 Hubble Space Telescope payload processing, testing and launch activities. He started his management career in 1990 supervising a group of engineers responsible for integrating experiments in the Spacelab Module. He later was assigned the position of Division Chief for the International Space Station Resupply and Return, where he was responsible for managing the development and delivery of the first Italian built Multi-Purpose Logistics Module (MPLM), Leonardo. In 1999, Rodríguez was requested to serve as the Chief of the Integration Office at Cape Canaveral Spaceport Management Office at the Cape Canaveral Air Force Station. He also led a team which developed a tool for capturing employee competencies and skills in support of the Agency Core Capabilities Assessment. In 2002, Rodríguez moved to Mississippi and to the NASA Stennis Space Center as the Director of Center Operations and as a member of the Senior Executive Service where he managed facility construction, security and other programs for 4,500 Stennis personnel. After a year, he was assigned to the position of Director of the Propulsion Directorate at Stennis Space Center located in Mississippiresponsible for providing the leadership and the safe operation of one of a kind national test facilities valued at over $2 billion, including the operations of several rocket engine propulsion test programs such as Space Shuttle Main Engine acceptance testing and the testing and evaluation of the next generation propulsion systems. His team worked on the STS-114 engines which were installed on the Discovery Space Shuttle launched in August 2005. In 2006, he returned to Kennedy Space Center, FL, as the
Miguel Rodríguez (NASA)
76653
Naval architecture, or naval engineering, is an engineering discipline incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the engineering design process, shipbuilding, maintenance, and operation of marine vessels and structures. Naval architecture involves basic and applied research, design, development, design evaluation (classification) and calculations during all stages of the life of a marine vehicle. Preliminary design of the vessel, its detailed design, construction, trials, operation and maintenance, launching and dry-docking are the main activities involved. Ship design calculations are also required for ships being modified (by means of conversion, rebuilding, modernization, or repair). Naval architecture also involves formulation of safety regulations and damage-control rules and the approval and certification of ship designs to meet statutory and non-statutory requirements. Main subjects The word "vessel" includes every description of watercraft, mainly ships and boats, but also including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water. The principal elements of naval architecture are detailed in the following sections. Hydrostatics Hydrostatics concerns the conditions to which the vessel is subjected while at rest in water and to its ability to remain afloat. This involves computing buoyancy, displacement, and other hydrostatic properties such as trim (the measure of the longitudinal inclination of the vessel) and stability (the ability of a vessel to restore itself to an upright position after being inclined by wind, sea, or loading conditions). Hydrodynamics Hydrodynamics concerns the flow of water around the ship's hull, bow, and stern, and over bodies such as propeller blades or rudder, or through thruster tunnels. Ship resistance and propulsion concern resistance towards motion in water primarily caused due to flow of water around the hull. Powering calculation is done based on this. Propulsion is used to move the vessel through water using propellers, thrusters, water jets, sails etc. Engine types are mainly internal combustion. Some vessels are electrically powered using nuclear or solar energy. Ship motions involves motions of the vessel in seaway and its responses in waves and wind. Controllability (maneuvering) involves controlling and maintaining position and direction of the vessel. Flotation and stability While atop a liquid surface a floating body has 6 degrees of freedom in its movements, these are categorized in either translation or rotation. Translation Sway: transverse Surge: fore and aft Heave: vertical Rotation Yaw: about a vertical axis Pitch or trim: about a transverse axis Roll or heel: about a fore and aft axis Longitudinal stability for longitudinal inclinations, the stability depends upon the distance between the center of gravity and the longitudinal meta-center. In other words, the basis in which the ship maintains its center of gravity is its distance set equally apart from both the aft and forward section of the ship. While a body floats on a liquid surface it still encounters the force of gravity pushing down on it. In order to stay afloat and avoid sinking there is an opposed force acting against the body known as the hydrostatic
Naval architecture
225170
The Gymnotiformes are an order of teleost bony fishes commonly known as Neotropical knifefish or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found almost exclusively in fresh water (the only exceptions are species that occasionally may visit brackish water to feed), these mostly nocturnal fish are capable of producing electric fields to detect prey, for navigation, communication, and, in the case of the electric eel (Electrophorus electricus), attack and defense. A few species are familiar to the aquarium trade, such as the black ghost knifefish (Apteronotus albifrons), the glass knifefish (Eigenmannia virescens), and the banded knifefish (Gymnotus carapo). Description Anatomy and locomotion Aside from the electric eel (Electrophorus electricus), Gymnotiformes are slender fish with narrow bodies and tapering tails, hence the common name of "knifefishes". They have neither pelvic fins nor dorsal fins, but do possess greatly elongated anal fins that stretch along almost the entire underside of their bodies. The fish swim by rippling this fin, keeping their bodies rigid. This means of propulsion allows them to move backwards as easily as they move forward. The knifefish has approximately one hundred and fifty fin rays along its ribbon-fin. These individual fin rays can be curved nearly twice the maximum recorded curvature for ray-finned fish fin rays during locomotion. These fin rays are curved into the direction of motion, indicating that the knifefish has active control of the fin ray curvature, and that this curvature is not the result of passive bending due to fluid loading. Different wave patterns produced along the length of the elongated anal fin allow for various forms of thrust. The wave motion of the fin resembles traveling sinusoidal waves. A forward traveling wave can be associated with forward motion, while a wave in the reverse direction produces thrust in the opposite direction. This undulating motion of the fin produced a system of linked vortex tubes that were produced along the bottom edge of the fin. A jet was produced at an angle to the fin that was directly related to the vortex tubes, and this jet provides propulsion that moves the fish forward. The wave motion of the fin is similar to that of other marine creatures, such as the undulation of the body of an eel, however the wake vortex produced by the knifefish was found to be a reverse Kármán vortex. This type of vortex is also produced by some fish, such as trout, through the oscillations of their caudal fins. The speed at which the fish moved through the water had no correlation to the amplitude of its undulations, however it was directly related to the frequency of the waves generated. Studies have shown that the natural angle between the body of the knifefish and its fin is essential for efficient forward motion, for if the anal fin was located directly underneath, then an upwards force would be generated with forward thrust, which would require an additional downwards force in order to maintain
Gymnotiformes
2724407
A rotor ship is a type of ship designed to use the Magnus effect for propulsion. The ship is propelled, at least in part, by large powered vertical rotors, sometimes known as rotor sails. German engineer Anton Flettner was the first to build a ship that attempted to tap this force for propulsion, and ships using his type of rotor are sometimes known as Flettner ships. The Magnus effect is a force acting on a spinning body in a moving airstream, which produces a force perpendicular to both the direction of the airstream and the axis of the rotor. Principles of operation A rotor or Flettner ship is designed to use the Magnus effect for propulsion. The Magnus Effect is caused by a spinning body in a moving airstream, or a moving body which is spinning (such as a ball), which pulls the air round to one side of the object, using the skin friction, creating a difference in air pressure from one side to the other. This causes a sideways force on the object making the spinning body move towards the low pressure side where there is least resistance. On a ship, this sideways force is resisted by the hull, and a component of this force can be used to propel the ship forward, provided that the ship's direction is generally within the low pressure zone. A Magnus rotor used to propel a ship is called a rotor sail and is mounted with its axis vertical. When the wind blows from the side, the Magnus effect creates a forward thrust. The most common form of rotor sail is the Flettner rotor. The wind does not power the rotor, which is rotated by its own power source. Due to the arrangement of forces, a rotor ship is able to sail closer to the wind than a conventional sailing ship. Other advantages include the ease of control from sheltered navigation stations and the lack of furling requirements in heavy weather. If the ship changes tack so that the wind comes from the other side, the direction of rotation must be reversed; the ship would otherwise be propelled backwards. Sailing ships, including rotor ships, often also have a small conventional propeller to provide ease of manoeuvrability and forward propulsion at slow speeds and when the wind is not blowing or the rotor is stopped. In a hybrid rotor ship the propeller is the primary source of propulsion, while the rotor serves to offload it and thus increase overall fuel economy. Rotor sails have been reported to generate 5-20% fuel savings. History Pioneers The German engineer Anton Flettner was the first to build a ship which attempted to use the Magnus effect for propulsion. The Buckau Assisted by Albert Betz, Jakob Ackeret, and Ludwig Prandtl, Flettner constructed an experimental rotor vessel; October 1924 the Germaniawerft finished construction of a large two-rotor ship named Buckau. The vessel was a refitted schooner which carried two cylinders (or rotors) approximately high, and in diameter, driven by
Rotor ship
595882
A diver propulsion vehicle (DPV), also known as an underwater propulsion vehicle, sea scooter, underwater scooter, or swimmer delivery vehicle (SDV) by armed forces, is an item of diving equipment used by scuba divers to increase range underwater. Range is restricted by the amount of breathing gas that can be carried, the rate at which that breathing gas is consumed, and the battery power of the DPV. Time limits imposed on the diver by decompression requirements may also limit safe range in practice. DPVs have recreational, scientific and military applications. DPVs include a range of configurations from small, easily portable scooter units with a small range and low speed, to faired or enclosed units capable of carrying several divers longer distances at higher speeds. The earliest recorded DPVs were used for military purposes during World War II and were based on torpedo technology and components. Structure A DPV usually consists of a pressure-resistant watertight casing containing a battery-powered electric motor, which drives a propeller. The design must ensure that the propeller cannot harm the diver, diving equipment or marine life, the vehicle cannot be accidentally started or run away from the diver, and it remains approximately neutrally buoyant while in use underwater. Application DPVs are useful for extending the range of an autonomous diver that is otherwise restricted by the amount of breathing gas that can be carried, the rate at which that breathing gas is consumed, which is increased by exertion and diver fatigue, and the time limits imposed by decompression obligation, which depend on the dive profile. Typical uses include cave diving and technical diving where the vehicles help move bulky equipment and make better use of the limited underwater time imposed by the decompression requirements of deep diving. Military applications include delivery of combat divers and their equipment over distances or at speeds that would be otherwise impracticable. There are accessories that can be mounted to a DPV to make it more useful, such as lights, compasses, and video cameras. Use of a DPV on deep dives can reduce the risk of hypercapnia from overexertion and high breathing rate. Limitations DPV operation requires greater situational awareness than simply swimming, as some changes can happen much faster. Operating a DPV requires simultaneous depth control, buoyancy adjustment, monitoring of breathing gas, and navigation. Buoyancy control is vital for diver safety: The DPV has the capacity to dynamically compensate for poor buoyancy control by thrust vectoring while moving, but on stopping the diver may turn out to be dangerously positively or negatively buoyant if adjustments were not made to suit the changes in depth while moving. If the diver does not control the DPV properly, a rapid ascent or descent under power can result in barotrauma or decompression sickness. High speed travel in confined spaces, or limited visibility can increase the risk of impact with the surroundings at speeds where injury and damage are more likely. Many forms of smaller marine life are very well camouflaged or hide well and
Diver propulsion vehicle
42092316
The Propulsion Wind Tunnel Facility, located at Arnold Engineering Development Complex, Arnold Air Force Base, Tennessee, holds three wind tunnels: the 16-foot transonic (16T), 16-foot supersonic (16S), and the aerodynamic 4-foot transonic (4T) tunnels. The facility is devoted to aerodynamic and propulsion integration testing of large-scale aircraft models. The tunnels are powered by a large compressor plant which allows the wind tunnels to run for extended periods of time. The test unit is owned by the United States Air Force and operated by Aerospace Testing Alliance. The wind tunnel test facility has been designated a landmark by the American Society of Mechanical Engineers because of its engineering significance. Propulsion Wind Tunnel 16T 16T is a transonic wind tunnel that can be configured for Mach numbers from 0.05 to 1.60. It is primarily used to test aerodynamics, propulsion integration, and weapons integration test capabilities that are needed for accurate prediction of flight system performance. The 16-foot-square, 40-foot long test section can simulate unit Reynolds numbers from approximately 0.03 to 7.3 million per foot or altitude conditions from sea level to 76,000 feet. The tunnel can also test air-breathing engines and rockets through the use of a scavenging system to remove exhaust from the flow stream. Propulsion Wind Tunnel 16S 16S is a supersonic wind tunnel that can be configured for Mach numbers from 1.5 to 4.750. The test section is also 16-foot-square and 40-foot long. The facility can simulate unit Reynolds numbers from approximately 0.1 to 2.4 million per foot or altitude conditions from 43,000 to 154,000 feet. Currently 16S is in the standby state. 16S ran again for the first time in more than 10 years on May 7, 2015, after an 18 month return to service effort. Aerodynamic Wind Tunnel 4T 4T is a transonic wind tunnel test unit which has a 4-ft by 4-ft by 12.5-ft long test section. Mach number capability extends from 0.2 to 2.0. The tunnel can simulate altitudes from sea level to 98,000 feet and can provide Reynolds numbers up to 7.1 million per foot. See also Subsonic and transonic wind tunnel References External links Arnold Engineering Development Center (official) Wind tunnels Research installations of the United States Air Force Military in Tennessee
Propulsion Wind Tunnel Facility
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Field propulsion is the concept of spacecraft propulsion where no propellant is necessary but instead momentum of the spacecraft is changed by an interaction of the spacecraft with external force fields, such as gravitational and magnetic fields from stars and planets. Proposed drives that use field propulsion are often called a reactionless or propellantless drive. Types Practical methods Although not presently in wide use for space, there exist proven terrestrial examples of "Field Propulsion", in which electromagnetic fields act upon a conducting medium such as seawater or plasma for propulsion, is known as magnetohydrodynamics or MHD. MHD is similar in operation to electric motors, however rather than using moving parts or metal conductors, fluid or plasma conductors are employed. The EMS-1 and more recently the Yamato 1 are examples of such electromagnetic Field propulsion systems, first described in 1994. There is definitely potential to apply MHD to the space environment such as in experiments like NASA's electrodynamic tether, Lorentz Actuated Orbits, the wingless electromagnetic air vehicle, and magnetoplasmadynamic thruster (which does use propellant). Electrohydrodynamics is another method whereby electrically charged fluids are used for propulsion and boundary layer control such as ion propulsion Other practical methods which could be loosely considered as field propulsion include: The gravity assist trajectory, which uses planetary gravity fields and orbital momentum; Solar sails and magnetic sails use respectively the radiation pressure and solar wind for spacecraft thrust; Aerobraking uses the atmosphere of a planet to change relative velocity of a spacecraft. The last two actually involve the exchange of momentum with physical particles and are not usually expressed as an interaction with fields, but they are sometimes included as examples of field propulsion since no spacecraft propellant is required. An example is the Magsail magnetic sail design. Speculative methods Other concepts that have been proposed are speculative, using "frontier physics" and concepts from modern physics. So far none of these methods have been unambiguously demonstrated, much less proven practical. The Woodward effect is based on a controversial concept of inertia and certain solutions to the equations for General Relativity. Experiments attempting to conclusively demonstrate this effect have been conducted since the 1990s. In contrast, examples of proposals for field propulsion that rely on physics outside the present paradigms are various schemes for faster-than-light, warp drive and antigravity, and often amount to little more than catchy descriptive phrases, with no known physical basis. Until it is shown that the conservation of energy and momentum break down under certain conditions (or scales), any such schemes worthy of discussion must rely on energy and momentum transfer to the spacecraft from some external source such as a local force field, which in turn must obtain it from still other momentum and/or energy sources in the cosmos (in order to satisfy conservation of both energy and momentum). Several people have speculated that the Casimir effect could be used to create a propellantless drive, often described as the "Casimir Sail", or a "Quantum Sail". Field propulsion based on physical structure
Field propulsion
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A shrimp (: shrimp (US) or shrimps (UK)) is a crustacean (a form of shellfish) with an elongated body and a primarily swimming mode of locomotion – typically belonging to the Caridea or Dendrobranchiata of the order Decapoda, although some crustaceans outside of this order are also referred to as "shrimp". More narrow definitions may be restricted to Caridea, to smaller species of either group or to only the marine species. Under a broader definition, shrimp may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long, narrow muscular tails (abdomens), long whiskers (antennae), and slender legs. Any small crustacean which resembles a shrimp tends to be called one. They swim forward by paddling with swimmerets on the underside of their abdomens, although their escape response is typically repeated flicks with the tail driving them backwards very quickly. Crabs and lobsters have strong walking legs, whereas shrimp have thin, fragile legs which they use primarily for perching. Shrimp are widespread and abundant. There are thousands of species adapted to a wide range of habitats. They can be found feeding near the seafloor on most coasts and estuaries, as well as in rivers and lakes. To escape predators, some species flip off the seafloor and dive into the sediment. They usually live from one to seven years. Shrimp are often solitary, though they can form large schools during the spawning season. They play important roles in the food chain and are an important food source for larger animals ranging from fish to whales. The muscular tails of many shrimp are edible to humans, and they are widely caught and farmed for human consumption. Commercial shrimp species support an industry worth 50 billion dollars a year, and in 2010 the total commercial production of shrimp was nearly 7 million tonnes. Shrimp farming became more prevalent during the 1980s, particularly in China, and by 2007 the harvest from shrimp farms exceeded the capture of wild shrimp. There are significant issues with excessive bycatch when shrimp are captured in the wild, and with pollution damage done to estuaries when they are used to support shrimp farming. Many shrimp species are small as the term shrimp suggests, about long, but some shrimp exceed . Larger shrimp are more likely to be targeted commercially and are often referred to as prawns, particularly in the Commonwealth of Nations and former British colonies. Classification Shrimp are swimming crustaceans with long narrow muscular abdomens and long antennae. Unlike crabs and lobsters, shrimp have well developed pleopods (swimmerets) and slender walking legs; they are more adapted for swimming than walking. Historically, it was the distinction between walking and swimming that formed the primary taxonomic division into the former suborders Natantia and Reptantia. Members of the Natantia (shrimp in the broader sense) were adapted for swimming while the Reptantia (crabs, lobsters, etc.) were adapted for crawling or walking. Some other groups also have common names that include the word "shrimp"; any small swimming crustacean resembling a shrimp tends to be called
Shrimp
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Edward George Gibson (born November 8, 1936) is a former NASA astronaut, pilot, engineer, and physicist. Before becoming an astronaut, Gibson graduated from the University of Rochester and the California Institute of Technology. He became a research assistant in jet propulsion while completing his studies, and eventually became a research scientist for Philco Corporation until joining NASA in 1965. Gibson is the last surviving crew member of Skylab 4. Gibson was selected as part of NASA Astronaut Group 4, the first group of scientist-astronauts. He served on the support crew of Apollo 12, the second Moon landing mission, before working on the development of the Skylab space station. In 1973–74, Gibson made his only flight into space as science pilot aboard Skylab 4, the third and final crewed flight to Skylab. He, along with Commander Gerald Carr and Pilot William Pogue, spent just over 84 days in space. Gibson resigned from NASA in December 1974, but returned in 1977 to preside over the selection of scientist-astronaut candidates. Gibson retired from NASA for the last time in October 1982. Early life and education Gibson was born in Buffalo, New York, on November 8, 1936. From ages 2 to 8, Gibson battled osteomyelitissoft spots in bonesand spent many months in and out of hospitals. Newly-available penicillin cured the disease. To strengthen his leg that was nearly amputated, Gibson took up sports: swimming, football, and track. He primarily used swimming to strengthen his leg. He was active in the Boy Scouts of America. He earned the rank of First Class. Gibson graduated from Kenmore Senior High School in Kenmore, New York, in 1955, and earned a Bachelor of Science degree in engineering from the University of Rochester in June 1959. At the University of Rochester, Gibson became a member of the Theta Chi fraternity. He received a Master of Science degree in engineering (jet propulsion option) from the California Institute of Technology (Caltech) in June 1960 and a PhD in engineering with a minor in physics from Caltech in June 1964. He was supervised by Maria Wonenburger. Early career While studying at Caltech, Gibson was a research assistant in the field of jet propulsion and classical physics. His technical publications are in the fields of plasma physics and solar physics. He was senior research scientist with the Applied Research Laboratories of the Philco Corporation at Newport Beach, California, from June 1964 until moving to NASA. While at Philco, he did research in lasers and the optical breakdown of gases. Gibson has logged more than 4,300 hours flying time—2,270 hours in jet aircraft. NASA career Gibson was selected as a scientist-astronaut by NASA in June 1965. He completed a 53-week course in flight training at Williams Air Force Base, Arizona, and earned his Air Force wings. Since then, he has flown helicopters and the T-38. He served as a member of the astronaut support crew and as a CAPCOM for the Apollo 12 lunar landing, becoming the first from the scientist-astronaut group to get
Edward Gibson
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Agni-Prime or Agni-P (Sanskrit: अग्नि; IAST: Agni; lit. Fire) is a two-stage, surface to surface, canister-launched, road mobile and solid-fueled medium-range ballistic missile being developed by India's Defence Research and Development Organisation (DRDO) as the sixth missile in the Agni series. It is intended to be deployed in the operational service of the Strategic Forces Command, and to feature significant upgrades to the composite motor casing, a maneuverable reentry vehicle (MaRV) along with improved propellants, navigation and guidance systems. History In 2016, Indian media began reporting that DRDO was developing a successor to the Agni-I called Agni-1P, which would feature two stages that borrowed the newer technologies from Agni-IV and Agni-V to increase accuracy and reliability. According to a senior scientist from the DRDO's missile complex in Hyderabad: India started working on area denial weapons after China developed the DF-21D and DF-26B ballistic missiles with nuclear capability to counter the US Navy, as well as capable of threatening Andersen Air Force Base. As a counterbalance, the progress of Agni-P became a crucial part of India's Indo-Pacific strategy to tackle China's plan of having five or six aircraft carrier battle groups by 2035 to cover both the Pacific Ocean and Indian Ocean. Description Propulsion Agni-P is a two-stage, solid-propellant missile. All stages uses composite propellant, where the powder oxidizer is mixed with a metal fuel along with a bind being put in place. Aluminium is used as fuel; its specific energy density gives it the capability to deliver high performance. This gives the missile, a better payload ratio and thus a larger payload that has been mounted on a missile can be lifted up with a less quantity of propellant. It is a new class of missile in Agni Series which is half the weight of Agni-III. Both first and second stage of Agni-P are made up of corrosion free composite material for the purpose of weight reduction, which was mastered during Agni-V project. Range and Mobility The missile can cover a maximum distance of 2000 km with 1.5 ton payload. According to analysts, Agni-P is primarily aimed at countering Pakistan's forces owing to the fact that its range is insufficient to reach all parts of mainland China. Given the missile's range, analysts at the International Institute for Strategic Studies believe that Agni-P primarily counters Pakistan and intends to replace older and less compact short-range ballistic missiles such as the Agni-I and Agni-II. The missile is stored in a hermetically sealed tandem twin canister launcher and is transported through road and rail. This process enables the warhead to be mated and stored with the missile, significantly reducing the time required for preparation and launch. It uses cold launch mechanism and can be fired in salvo mode. When a cold launch of a canisterised missile is done and when it uses a solid propellant, then it would be an edge for India for conducting nuclear strikes in a shorter amount of time from any terrain. The test launches of the missile seemingly
Agni-P
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Samaridae (crested flounders) is a family of crested flounders, small flatfishes native to the Indo-Pacific. The family contains four genera with a total of 29 species. Taxonomy Samaridae is one of eight families a part of the SuperFamily Soleioidea. This SuperFamily is of the suborder Pleuronectoidei within the order Pleuronectiformes. Samaridae were formerly classified as a subfamily of Pleuronectidae. Anatomy and morphology Young flat fish are bilaterally symmetrical until they reach between 5 and 120mm in length when one eye shifts from the lower side to the upper side until it is adjacent to the other eye. Adult flat fish swim and lie on the side without eyes. Adult Samaridae are not bilaterally symmetrical but do have symmetrical pelvic fins. They have a highly compressed body with eyes that bulge above the body surface which allows them to see out while buried beneath a surface. Samaridae have countershaded coloring with a darker pigment on the top of the fish and a lighter pigment on bottom. They have a stabilizing dorsal fin on top of the fish that stems from a point in front of the eyes. They have a basic lateral line organ to detect the movement of the water around them and lack a postcletherium. Samaridae can range between 4 and 23 centimeters at length depending on the species. Samaridae have no spines in their fins with a protruding lower jaw and an asymmetrical nose located on the lower side opposite the eyes. Habitat The Samaridae are native to marine areas in the Indo-Pacific region, from South Africa to Hawaii and New Caledonia. They are found in tropical and subtropical areas in deep-water Benthic zones. They are found in saltwater only. Samaridae can also be found near coastal regions with coral reefs up to depths of 150 meters. Behavior Locomotion Samaridae are negatively buoyant and while they are able to swim through the water column, they spend most of their time on the ocean floor. While swimming, the flatfish keeps its head up through a mechanism of support from the median, pectoral, and pelvic fins. Samaridae move across the sea floor through propulsion by the tail and assisted by the pectoral fins. Flatfish move into the water column by turning its body and propelling itself upwards through propulsion by the tail and body, and continue to move via the "swim and glide" method of short bursts of propulsion. Burying One way that Samaridae avoid predation is by burying themselves underneath the sand on the ocean floor. They do this by repeatedly hitting their head and body against the sand so it lifts up and falls down on top of the flatfish. This process lasts only a few seconds and is a very effective tool in avoiding detection by predators. Reproduction Samaridae reach sexual maturity between 1 and 15 years of age. Flatfish reproduction takes place over 3 stages: courtship, spawning rise, and a post-spawning return to the sea floor. In Courtship, male flatfish follow female flatfish to the bottom
Samaridae
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The Shivering Truth is an American adult stop-motion animated anthology horror comedy television series created by Vernon Chatman and directed by Chatman and Cat Solen. The show is produced by Solen with PFFR and ShadowMachine, and features a wide range of voice talents besides Chatman, including Janeane Garofalo, Jonah Hill, Trey Parker, David Cross, Jordan Peele, Kyle Mooney, Julia Davis, Tierra Whack, Will Forte, and Josh Gad, amongst others. The Shivering Truth premiered on December 10, 2018 on Cartoon Network's late-night programming block Adult Swim, with the pilot episode having been released online on May 22, 2018 on the Adult Swim website. In November 2019, Adult Swim renewed the series for a second season, which premiered on May 10, 2020. Overview When announced in a press release by Adult Swim in May 2017, The Shivering Truth was described as "a delicately crafted, darkly surreal anthology comedy, a miniature propulsive omnibus cluster bomb of painfully riotous daymares all dripping with the orange goo of dream logic. A series of loosely-linked emotional parables about stories within tales that crawled out of the deepest caverns of your unconscious mind and became lovingly animated in breath-slapping stop motion – in other words, it is the TRUTH". Development The characters in the show are puppets with wire-based armatures, created with silicone, wool, polystyrene, and resin. Chatman stated that around six months of physical production, a month of recording, and months of post-production were needed to complete six episodes. Chatman has noted several inspirations for his work on the show, including Terry Gilliam's work on Monty Python's Flying Circus, stating that "I saw it when I was very young, so it scared me. I didn't know when the animation was beginning or ending." He also explained that "A lot of my influences are non-animated, primarily in short films, novels, even radio shows. A recent one is David Eagleman's books on the brain. He's a neuroscientist and he gives you 40 different versions of the afterlife, and none of them can co-exist." Solen has spoken on her inspirations as well, saying that "I loved the movie The Wizard of Speed and Time, which is a cautionary tale about making movies. Another film that I loved as a kid was Nicolas Roeg's [film] adaptation of Roald Dahl's The Witches, which featured both Anjelica Huston and Jim Henson's puppets. It scared me so much!" Cast Season 1 Season 2 Music The song played during the closing credits is usually some version of the old English ballad Long Lankin. The music is often distorted in some way and usually begins near the end of the ballad, at the lines "There's blood in the kitchen, there's blood in the hall / There's blood in the parlour where my lady did fall." The original score is by Heather Christian. Episodes Series overview Pilot (2018) Season 1 (2018) Season 2 (2020) Release The pilot episode premiered on the Adult Swim website on May 22, 2018. Before the television premiere on December 10, 2018,
The Shivering Truth
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USS Remora (SS-487), a , was the only ship of the United States Navy to be named for the remora, a fish with a suctorial disk on its head enabling it to cling to other fish and to ships. Construction and commissioning Remora′s keel was laid down on 5 March 1945 by the Portsmouth Navy Yard in Kittery, Maine. She was launched on 12 July 1945, sponsored by Mrs. T. W. Samuels III, and commissioned on 3 January 1946 with Commander Robert Sellars in command. Service history Training submarine Completing her Caribbean Sea shakedown in April 1946, Remora operated out of New London, Connecticut, as a training submarine until January 1947. Then transferred to the Pacific, she transited the Panama Canal at mid-month and arrived at Mare Island, Vallejo, California, on 14 February to begin a Greater Underwater Propulsive Power Program (GUPPY-II) conversion. Early in November, she completed trials and on 22 February arrived at San Diego, California, her new homeport. Eastern Pacific For the next two years, she remained in the eastern Pacific operating primarily off California, but during the summer and early fall of 1948, ranged as far north as the Aleutian Islands. On 1 May 1950 she headed west for her first deployment in the Far East. On 8 June she arrived at Sasebo, and on 11 June she shifted to Yokosuka, from which base she conducted anti-submarine warfare (ASW) training exercises with units of Naval Forces Far East. Two weeks later the Korean War began. A unit of TF 96, Naval Forces Japan Remora patrolled Soya Strait, between Hokkaidō and Sakhalin in late July and early August. Later in the month, she headed back to San Diego. During the next two years she underwent overhaul, provided services for the Line School at Monterey, California, and conducted local training exercises. She returned to the western Pacific in early 1953. Arriving at Buckner Bay on 15 March, she continued on to Japan in April and at mid-month rejoined TF 96. In June she was back in Okinawan waters for patrols and exercises, after which she returned to Yokosuka. On 2 July she headed east, reaching San Diego on 3 August. After the fighting in Korea ended, Remora remained based at San Diego and through the decade continued to alternate training exercises and patrols in the western Pacific with similar First Fleet operations off the United States West Coast and in Hawaiian waters. She remained in the eastern Pacific during 1956 and 1958, but, during the spring of the latter year, was engaged in extended exercises off Alaska. Pearl Harbor In November 1961, Remora was transferred from San Diego to Pearl Harbor. The following year she underwent a seven-month Greater Underwater Propulsive Power Program (GUPPY-III) conversion which lengthened her hull by and her conning tower by five feet. Then, in 1963, she was employed to evaluate antisubmarine sonar in Hawaiian waters. In May 1964, she resumed a schedule of annual six-month WestPac deployments which she continued into 1969. Remora
USS Remora
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Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body and tail in the water, and in various specialised fish by motions of the fins. The major forms of locomotion in fish are: Anguilliform, in which a wave passes evenly along a long slender body; Sub-carangiform, in which the wave increases quickly in amplitude towards the tail; Carangiform, in which the wave is concentrated near the tail, which oscillates rapidly; Thunniform, rapid swimming with a large powerful crescent-shaped tail; and Ostraciiform, with almost no oscillation except of the tail fin. More specialized fish include movement by pectoral fins with a mainly stiff body, opposed sculling with dorsal and anal fins, as in the sunfish; and movement by propagating a wave along the long fins with a motionless body, as in the knifefish or featherbacks. In addition, some fish can variously "walk" (i.e., crawl over land using the pectoral and pelvic fins), burrow in mud, leap out of the water and even glide temporarily through the air. Swimming Mechanism Fish swim by exerting force against the surrounding water. There are exceptions, but this is normally achieved by the fish contracting muscles on either side of its body in order to generate waves of flexion that travel the length of the body from nose to tail, generally getting larger as they go along. The vector forces exerted on the water by such motion cancel out laterally, but generate a net force backwards which in turn pushes the fish forward through the water. Most fishes generate thrust using lateral movements of their body and caudal fin, but many other species move mainly using their median and paired fins. The latter group swim slowly, but can turn rapidly, as is needed when living in coral reefs for example. But they can not swim as fast as fish using their bodies and caudal fins. Consider the tilapia shown in the diagram. Like most fish, the tilapia has a streamlined body shape reducing water resistance to movement and enabling the tilapia to cut easily through water. Its head is inflexible, which helps it maintain forward thrust. Its scales overlap and point backwards, allowing water to pass over the fish without unnecessary obstruction. Water friction is further reduced by mucus which tilapia secrete over their body. The backbone is flexible, allowing muscles to contract and relax rhythmically and bring about undulating movement. A swim bladder provides buoyancy which helps the fish adjust its vertical position in the water column. A lateral line system allows it to detect vibrations and pressure changes in water, helping the fish to respond appropriately to external events. Well developed fins are used for maintaining balance, braking and changing direction. The pectoral fins act as pivots around which the fish can turn rapidly and steer itself. The paired pectoral and pelvic fins control
Fish locomotion
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Certain species of fish and birds are able to locomote in both air and water, two fluid media with very different properties. A fluid is a particular phase of matter that deforms under shear stresses and includes any type of liquid or gas. Because fluids are easily deformable and move in response to applied forces, efficiently locomoting in a fluid medium presents unique challenges. Specific morphological characteristics are therefore required in animal species that primarily depend on fluidic locomotion. Because the properties of air and water are so different, swimming and flying have very disparate morphological requirements. As a result, despite the large diversity of animals that are capable of flight or swimming, only a limited number of these species have mastered the ability to both fly and swim. These species demonstrate distinct morphological and behavioral tradeoffs associated with transitioning from air to water and water to air. Flying birds Of extant species, only insects, birds, and bats are capable of true, sustained, powered flight. Aerodynamic principles For birds to achieve flight, they must first successfully overcome the downward pull of gravitational forces by producing lift. This is achieved by positioning or moving their wings in a way that makes the pressure below the wings higher than above the wings. This pressure differential creates a net upward force on the wing, thus allowing the bird to lift off the ground, provided the upward force exceeds its weight. To achieve powered flight, forward flight birds must counteract drag forces that act opposite the direction of flight. Drag forces acting on a flying animal are composed of parasitic drag on the body fuselage and induced drag on the wings, both acting against the relative direction of flight. Adjusting the angle of attack while wing beat frequency is held constant, birds are able to direct a component of the lift produced by their wings backwards, thus producing propulsive force known as thrust. Evolution of flight There are many competing theories explaining the evolution of avian flight. The most widely accepted theories include: Cursorial model: wings evolved as a stabilization mechanism for progressively longer jumps in running bipeds. Arboreal model: the earliest ancestors of birds were gliders rather than true fliers. Much like modern-day flying squirrels, early avian ancestors were thought to climb up trees and then glide down from the tree tops. Pouncing Proavis model: Similar to the arboreal model, this model proposes that early predators attacked from above and evolved wings to assist in stabilizing their descent when pouncing on prey. Wing-assisted incline running (WAIR): suggests that wings evolved to provide additional downward force to increase traction during fast ascent of steep slopes in chicks. Novel association of locomotor modules: A theory introduced by Gatesy and Dial in 1996 attempts to explain how birds were capable of developing wings that eventually led to the ability of true flight. They introduce the idea of "locomotor modules" as anatomical groupings (i.e. two legs) working together as a single functional neuromuscular unit for locomotion. The
Tradeoffs for locomotion in air and water
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The flutter kick is a kicking movement used in both swimming and calisthenics. Swimming In swimming strokes such as the front crawl or backstroke, the primary purpose of the flutter kick is not propulsion but keeping the legs up and in the shadow for the upper body and assisting body rotation for arm strokes. The legs are extended straight backwards in line with the body. They are moved up and down, one leg kicking downwards (relative to the front of the swimmer's body) as the other leg moves up. The knees are slightly bent to facilitate the kicking action, but not too much in order to minimize drag created by the thighs as they move out of the shadow of the swimmer's body. Similarly, toes are pointed to minimize drag. The downward moving leg provides the thrust. An integral part of the kick is the flexing of the ankles; it is the flexing of the ankle that allows the foot to provide thrust. The knees are not kept rigid when kicking but are allowed to flex slightly to allow the required "snapping" action through the end of the toes. Underwater diving The flutter kick used with swimfins can be a powerful propulsion technique, and is used by scuba divers and freedivers underwater and at the surface, but there are other finning techniques more appropriate to some underwater environments and some types of fin. Divers in a confined environment or where silting may be a problem may use a modified flutter kick or frog kick, done entirely with bent knees, pushing water up and behind the diver to avoid stirring up sediment on the bottom. Calisthenics The calisthenics version of the flutter kick is often used as an intensive training tool in the military. They help to develop the hip flexors, abdominal muscles and leg muscles. Flutter kicks are a four-count exercise. Starting position is lying flat on the back with the feet and head approximately 6 inches (15 cm) off the ground. Hands are under the buttocks to support the lower back. Count one: raise the left leg to a 45-degree angle, keeping the right leg stationary. Count two: raise the right leg off the ground to a 45-degree angle while, at the same time, moving the left leg to the starting position. Counts three and four are repetitions of the same movements. Legs must be locked, with toes pointing away from the body. References Swimming styles
Flutter kick
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The Tripartite class is a class of minehunters developed from an agreement between the navies of Belgium, France and the Netherlands. A total of 35 ships were constructed for the three navies. The class was constructed in the 1980s–1990s in all three countries, using a mix of minehunting, electrical and propulsion systems from the three member nations. In France, where they are known as the Éridan class they are primarily used as minehunters, but have been used for minesweeping and ammunition transport in Belgium and the Netherlands, where the Tripartites are known as the . In 1992, the Pakistan Navy acquired three vessels from France, one that was already built, one to be built in France and one built in France and Pakistan. Known as the Munsif class, all three are still in service. The Indonesian Navy acquired two minehunters in the 1990s from the Dutch to a modified design. Known as the Pulau Rengat class, the two ships are still in service. In 1997, France purchased three of the Belgian vessels. In 2007, the Latvian Naval Forces acquired five ships from the Netherlands which had been taken out of service at the beginning of the decade. The Bulgarian Navy acquired a former Belgian minehunter in 2007. The Netherlands and Belgium had a competition in 2018 to build a replacement class for their Tripartite/Alkmaar-class ships. Design and development A joint venture of the navies of France, Belgium, and the Netherlands, the Tripartite class of minehunters were a follow on design to the French s. All three nations would build their own hulls while each country was responsible for a different aspect of the vessels; France provided the minehunting and electronic systems, the Netherlands provided the main propulsion systems and Belgium supplied the minehunting propulsion system as well as the electrical generating systems. Each country intended to order 15 of the vessels, with Belgium's initial order being 10 with the option of 5 more. However, France cut their initial order to ten due to budgetary reasons. Ships France In France the class is known as the Éridan class. Each hull was created from fibreglass, moulded in a steel shell. The hulls were long overall with a beam of and a draught of . The ships had a standard displacement of and at full load. This later increased to at full load. A container can be stored aboard the ships for additional supply room. The minehunters had an initial complement of 55, this was later reduced to 49. The Éridan-class minehunters have two independent propulsion systems. In normal operations the minehunters are powered by a Brons-Werkspoor (later Wärtsilä) A-RUB 215V-12 diesel engine turning one shaft with a LIPS controllable pitch propeller. Using the conventional system, the minehunters have a maximum speed of and a range of at . For use when minehunting the vessels have two ACEC active rudders and a bow thruster. These are energised by three Astazou IVB gas turbine alternators rated at 150 kW. A fourth diesel-driven alternator rated
Tripartite-class minehunter
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A marine thruster is a device for producing directed hydrodynamic thrust mounted on a marine vehicle, primarily for maneuvering or propulsion. There are a variety of different types of marine thrusters and each of them plays a role in the maritime industry. Marine thrusters come in many different shapes and sizes, for example screw propellers, Voith-Schneider propellers, waterjets, ducted propellers, tunnel bow thrusters, and stern thrusters, azimuth thrusters, rim-driven thrusters, ROV and submersible drive units. A marine thruster consists of a propeller or impeller which may be encased in some kind of tunnel or ducting that directs the flow of water to produce a resultant force intended to obtain movement in the desired direction or resist forces which would cause unwanted movement. The two subcategories of marine thrusters are for propulsion and maneuvering, the maneuvering thruster typically in the form of bow or stern thrusters and propulsion thrusters ranging from Azimuth thrusters to Rim Drive thrusters. Positioning Thrusters Positioning thrusters come in applications, Bow thrusters at the forward end of the vessel, and stern thrusters mounted aft on the boat. Their purpose is to maneuver or position the boat to a greater precision than the propulsion device can accomplish. Their positioning along the length of the vessel allows for directed lateral thrust ahead and astern of the centre of lateral resistance so that the vessel may be maneuvered away from obstructions in its path, or towards a desired position, especially when coming to or away from a dock. These positioning thrusters are usually significantly smaller than the main propulsion thrusters because they only have to do small adjustments rather than moving the whole vessel at speed. Both bow and stern thrusters may be housed in through-hull tunnels. Depending on the size of the motors driving these propellers, they could draw an insignificant amount of power or a large amount of power that requires much caution to operate. Another smaller subset of positioning thrusters is those used for maneuvering unmanned aquatic vehicles like Guanay II AUV tested by scientists from Spain (Masmitja, 2018). Propulsion Thrusters Propulsion thrusters are those thrusters which provide longitudinal motion for vessels as an alternative to traditional propellers. There are a variety of types of propulsion thrusters but the most common form is the azimuth thruster, that can rotate 360 degrees on a vertical axis to optionally produce thrust for maneuvering. (Lindborg, 1997). The amount of thrust produced is controllable. There are variants of azimuth thrusters such as CRP thrusters which have two contra-rotating Azimuth thrusters or Swing-Up Azimuth thrusters that can be retracted when not in use to reduce drag on the vessel (Wartsila Encyclopedia). Other propulsion thrusters like outboard thrusters which can be easily put in and out of service, rim drive thrusters that are driven via the external ring with the blades mounted on the inner face of the ring with their tips towards the center, or tilted thrusters pointed away from the hull to minimize interaction with the ship and increase thruster efficiency.
Marine thruster
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A solar thermal rocket is a theoretical spacecraft propulsion system that would make use of solar power to directly heat reaction mass, and therefore would not require an electrical generator, like most other forms of solar-powered propulsion do. The rocket would only have to carry the means of capturing solar energy, such as concentrators and mirrors. The heated propellant would be fed through a conventional rocket nozzle to produce thrust. Its engine thrust would be directly related to the surface area of the solar collector and to the local intensity of the solar radiation. In the shorter term, solar thermal propulsion has been proposed both for longer-life, lower-cost, more efficient use of the sun and more-flexible cryogenic upper stage launch vehicles and for on-orbit propellant depots. Solar thermal propulsion is also a good candidate for use in reusable inter-orbital tugs, as it is a high-efficiency low-thrust system that can be refuelled with relative ease. Solar-thermal design concepts There are two solar thermal propulsion concepts, differing primarily in the method by which they use solar power to heat up the propellant: Indirect solar heating involves pumping the propellant through passages in a heat exchanger that is heated by solar radiation. The windowless heat exchanger cavity concept is a design taking this radiation absorption approach. Direct solar heating involves exposing the propellant directly to solar radiation. The rotating bed concept is one of the preferred concepts for direct solar radiation absorption; it offers higher specific impulse than other direct heating designs by using a retained seed (tantalum carbide or hafnium carbide) approach. The propellant flows through the porous walls of a rotating cylinder, picking up heat from the seeds, which are retained on the walls by the rotation. The carbides are stable at high temperatures and have excellent heat transfer properties. Due to limitations in the temperature that heat exchanger materials can withstand (approximately 2800 K), the indirect absorption designs cannot achieve specific impulses beyond 900 seconds (9 kN·s/kg = 9 km/s) (or up to 1000 seconds, see below). The direct absorption designs allow higher propellant temperatures and therefore higher specific impulses, approaching 1200 seconds. Even the lower specific impulse represents a significant increase over that of conventional chemical rockets, however, an increase that can provide substantial payload gains (45 percent for a LEO-to-GEO mission) at the expense of increased trip time (14 days compared to 10 hours). Small-scale hardware has been designed and fabricated for the Air Force Rocket Propulsion Laboratory (AFRPL) for ground test evaluation. Systems with 10 to 100 N of thrust have been investigated by SART. Reusable Orbital Transfer Vehicles (OTV), sometimes called (inter-orbital) space tugs, propelled by solar thermal rockets have been proposed. The concentrators on solar thermal tugs are less susceptible to radiation in the Van Allen belts than the solar arrays of solar electric OTV. An initial proof of concept was demonstrated in 2020 with helium at the Johns Hopkins University Applied Physics Laboratory solar simulator. Propellants Most proposed designs for solar thermal rockets use
Solar thermal rocket
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The Special Security and Protection Battalion (SPBN) () is a specialized unit of the Bangladesh Police. The battalion provides protection to the President of Bangladesh, Prime Minister of Bangladesh, and any person designated as VIP by the Government including visiting foreign dignitaries. It is also responsible for the security of VIPs’ offices and residences and venues of programs. It works alongside Special Security Force, Special Branch, Dhaka Metropolitan Police (DMP) and President Guard Regiment. Though it was formed on December 26, 2011, it formally started operation on 4 July 2013. Organization This specialized unit of Bangladesh Police is headed by a Deputy Inspector General of Police. Primarily, the SPBn has two specialized battalions each headed by a Superintendent of Police (Commanding Officer). Each battalion has 700 members including 12 additional superintendents, 15 assistant superintendents, 33 inspectors with sub-inspectors, assistant sub-inspectors, naek and constables. All the officers and personnel come from Bangladesh Police through an intensive selection procedure. Training It has primary responsibility for the safety of VIPs and visiting dignitaries to Bangladesh. Therefore, the compulsory training techniques taught to all SPBn officers/members include VIP protection and unarmed combat. They also undergo training in firearms, attack and ambush, motorcade protection, crowd control, self-defense, tactical driving, physical and tactical training, swimming, search and sweeping techniques, IED and EOD training, fire evacuation and crisis management and basic trauma life support. They practice simulation exercises in the firing range. Out of their internal training wing, the trainers from Special Security Force, President Guard Regiment, Fire Service and Civil Defense department and other training experts from Bangladesh Police conduct the training. The courses vary from two to six weeks. Mahiuddin Khan Alomgir, Minister of Home Affairs, inaugurated the first training course for the officers of SPBn. Vehicles Nissan Patrol Y61 and Toyota Land Cruiser 200 Series are the SUVs often deployed in protective missions. Weapons The standard issue sidearms for all SPBn is the Glock 17 and the Glock 19 while the short version of the Heckler & Koch MP5 is the standard SMG and could be deployed in multiple variants. SPBn started to use the SMT9 SMG from March 2015. Type 56 assault rifle also used by SPBn. Apart from firearms, ASP expandable batons or tasers are carried for less-than-lethal options to the SPBn officers. Stun grenades and smoke grenades are also used to provide cover for escorting the VIP when under attack. See also List of protective service agencies Special Security Force References Protective security units Law enforcement in Bangladesh Police units of Bangladesh Law enforcement agencies of Bangladesh
Special Security and Protection Battalion
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The Mark 37 torpedo is a torpedo with electrical propulsion, developed for the US Navy after World War II. It entered service with the US Navy in the early 1950s, with over 3,300 produced. It was phased out of service with the US Navy during the 1970s, and the stockpiles were sold to foreign navies. Development Its engineering development began in 1946 by Westinghouse. It was largely based on the concept of the passive homing Mark 27, with added active homing system tested on modified Mark 18s, and a new torpedo body. Between 1955 and 1956, thirty torpedoes were produced for development testing, with large-scale production commenced shortly afterwards. Due to its electric propulsion, the torpedo swam smoothly out of the launch tube, instead of having to be ejected by pressurized air, therefore significantly reducing its acoustic launch signature. To allow for water flow around the torpedo while swimming out, several 1" thick guide studs were attached to the torpedo, which although 19" in diameter was designed to be used only from 21" torpedo tubes. The guidance of a Mk37 mod 0 torpedo was done by a gyroscope control during the initial part of its trajectory, where the gyro control achieved a straight run, a passive sonar homing system, and at the last by a Doppler-enabled active sonar homing, with magnetostrictive transducers operating at 60 kHz. The electronics was based on miniature vacuum tubes, later on solid-state semiconductor devices. Modifications The mod 1 torpedoes were longer, slower and heavier than mod 0, but offered better target acquisition capabilities and higher ability to intercept agile submarines. They used wire-guidance. The efficiency of Mk37 torpedoes was high for targets with speed lower than and depth less than . As submarines with higher speeds and operating depths appeared, new torpedoes were developed. Of them, NT37C, D, E, and F are based on the Mk37 design. In 1967, the mod 0s started being refurbished as mod 3, and mod 1 as mod 2. These modifications involved many changes including replacement of magnetostrictive transducers with piezoelectric ones, and resulted in target acquisition range increased from to without loss of sensitivity with increasing depth. The torpedoes used Mark 46 silver-zinc batteries. These had a known tendency to overheat, occasionally igniting or exploding. Training torpedoes used rechargeable secondary batteries. For a long time, the Mark 37 was a primary U.S. submarine-launched ASW torpedo. It was replaced by the Mark 48 starting in 1972. The remaining inventory was then rebuilt and sold to several countries, including Israel, as the NT-37C after the vacuum tube guidance systems were replaced by solid-state electronics and the electric propulsion was replaced with a liquid monopropellant. Other uses The Mk 67 submarine launched mobile mine is based on a Mark 37 torpedo body. It entered service in 1983 and is capable of swimming as far as 10 miles through or into a channel, harbor, shallow water area and other zones which would normally be inaccessible to the vessel laying it. After reaching the
Mark 37 torpedo
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Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere (i.e. air flight or aviation) or through the vacuum of outer space (i.e. spaceflight). This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement. Many things can fly, from animal aviators such as birds, bats and insects, to natural gliders/parachuters such as patagial animals, anemochorous seeds and ballistospores, to human inventions like aircraft (airplanes, helicopters, airships, balloons, etc.) and rockets which may propel spacecraft and spaceplanes. The engineering aspects of flight are the purview of aerospace engineering which is subdivided into aeronautics, the study of vehicles that travel through the atmosphere, and astronautics, the study of vehicles that travel through space, and ballistics, the study of the flight of projectiles. Types of flight Buoyant flight Humans have managed to construct lighter-than-air vehicles that raise off the ground and fly, due to their buoyancy in the air. An aerostat is a system that remains aloft primarily through the use of buoyancy to give an aircraft the same overall density as air. Aerostats include free balloons, airships, and moored balloons. An aerostat's main structural component is its envelope, a lightweight skin that encloses a volume of lifting gas to provide buoyancy, to which other components are attached. Aerostats are so named because they use "aerostatic" lift, a buoyant force that does not require lateral movement through the surrounding air mass to effect a lifting force. By contrast, aerodynes primarily use aerodynamic lift, which requires the lateral movement of at least some part of the aircraft through the surrounding air mass. Aerodynamic flight Unpowered flight versus powered flight Some things that fly do not generate propulsive thrust through the air, for example, the flying squirrel. This is termed gliding. Some other things can exploit rising air to climb such as raptors (when gliding) and man-made sailplane gliders. This is termed soaring. However most other birds and all powered aircraft need a source of propulsion to climb. This is termed powered flight. Animal flight The only groups of living things that use powered flight are birds, insects, and bats, while many groups have evolved gliding. The extinct pterosaurs, an order of reptiles contemporaneous with the dinosaurs, were also very successful flying animals, and there were apparently some flying dinosaurs (see Flying and gliding animals#Non-avian dinosaurs). Each of these groups' wings evolved independently, with insects the first animal group to evolve flight. The wings of the flying vertebrate groups are all based on the forelimbs, but differ significantly in structure; those of insects are hypothesized to be highly modified versions of structures that form gills in most other groups of arthropods. Bats are the only mammals capable of sustaining level flight (see bat flight). However, there are several gliding mammals which are able to glide from tree to tree using fleshy membranes between their limbs; some can travel hundreds of meters
Flight
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Field-emission electric propulsion (FEEP) is an advanced electrostatic space propulsion concept, a form of ion thruster, that uses a liquid metal as a propellant – usually either caesium, indium, or mercury. A FEEP device consists of an emitter and an accelerator electrode. A potential difference of the order of 10 kV is applied between the two, which generates a strong electric field at the tip of the metal surface. The interplay of electric force and the liquid metal’s surface tension generates surface instabilities, which give rise to Taylor cones on the liquid surface. At sufficiently high values of the applied field, ions are extracted from the cone tip by field evaporation or similar mechanisms, which then are electrically accelerated to high velocities – typically 100 km/s or more. Although the ion exhaust velocity is high, their mass is very low, resulting in very weak acceleration forces. Their benefit comes from sustained acceleration forces over long time periods. Due to its very low thrust (in the micronewton (μN) to millinewton (mN) range), FEEP thrusters are primarily used for microradian, micronewton attitude control on spacecraft, such as in the ESA/NASA LISA Pathfinder scientific spacecraft. The FEEP thruster was also slated for installation on Gravity Field and Steady-State Ocean Circulation Explorer spacecraft, but the Gridded ion thruster was used instead. The first FEEP thruster operated in space was the IFM Nano Thruster, successfully commissioned in Low Earth Orbit in 2018. Basic concept Field emission electric propulsion (FEEP) is an electrostatic propulsion method based on field ionization of a liquid metal, and subsequent acceleration of the ions by a strong electric field. Sharp features such as needles are used to enhance and concentrate the strength of this electric field. The needle is coated in the liquid metal, maximising the acceleration of the ions. FEEP is currently the object of interest in the scientific community, due to its unique features: sub-μN to mN thrust range, near instantaneous switch on/switch off capability, and high-resolution throttleability (better than one part in 104), which enables accurate thrust modulation in both continuous and pulsed modes. Presently baseline for scientific missions onboard drag-free satellites, this propulsion system has also been proposed for attitude control and orbit maintenance on commercial small satellites and constellations. A separate electron source is required to keep the spacecraft electrically neutral. Liquid-metal propellants This type of thruster can accelerate a large number of different liquid metals or alloys. The best performance (in terms of thrust efficiency and power-to-thrust ratio) can be obtained using high atomic weight alkali metals, such as cesium (Cs, 133 amu) and rubidium (Rb, 85.5 amu). These propellants have a low ionization potential (3.87 eV for Cs and 4.16 eV for Rb), low melting point (28.7 °C for Cs and 38.9 °C for Rb) and very good wetting capabilities. These features lead to low power losses due to ionization and heating and the capability to use capillary forces for feeding purposes, i.e., neither pressurised tanks nor valves are required. Moreover, alkali metals have
Field-emission electric propulsion
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The water opossum (Chironectes minimus), also locally known as the yapok (), is a marsupial of the family Didelphidae. It is the only living member of its genus, Chironectes. This semiaquatic creature is found in and near freshwater streams and lakes from Mexico through Central and South America to Argentina and is the most aquatic living marsupial (the lutrine opossum also has semiaquatic habits). It is also the only living marsupial in which both sexes have a pouch. The thylacine, commonly referred to as the Tasmanian tiger, also exhibited this trait, but it is now extinct. The water opossum lives in bankside burrows, emerging after dusk to swim and search for fish, crustaceans and other aquatic animals, which it eats on the bank. Origin of the name The local name for the water opossum, "yapok", probably comes from the name of the Oyapok River in French Guiana. Physical appearance The water opossum is a small opossum, long, with a long tail. The fur is in a marbled grey and black pattern, while the muzzle, eyestripe, and crown are all black. A light band runs across the forehead anterior to the ears, which are rounded and naked. There are sensory facial bristles in tufts above each eye, as well as whiskers. The water opossum's tail, furred and black at the base, is yellow or white at its end. The hindfeet of the water opossum are webbed, while the forefeet ("hands") are not. The forefeet can be used to feel for and grab prey as the animal swims, propelled by its tail and webbed back feet. Unlike other didelphids, the water opossum does not have a cloaca. Aquatic adaptations The water opossum has several adaptations for its watery lifestyle. It has short, dense fur, which is water-repellent. The broad hindfeet are webbed and are used for propulsion through water, moving with alternate strokes. They are symmetrical as well, which distributes force equally along both borders of the webbing; this increases the efficiency of the water opossum's movement through the water. The water opossum's long tail also aids in swimming. Being a marsupial and at the same time an aquatic animal, the water opossum has evolved a way to protect its young while swimming. A strong ring of muscle makes the pouch (which opens to the rear) watertight, so the young remain dry, even when the mother is totally immersed in water. The male also has a pouch (although not as watertight as the female's), where he places his genitalia before swimming. This is thought to prevent them from becoming entangled in aquatic vegetation and is probably helpful in streamlining the animal as well. Reproduction Water opossums mate in December and a litter of 1–5 young is born 12 to 14 days later in the nest. By 22 days the offspring are beginning to show some fur, and by 40 days or so their eyes are open, their bodies protruding from the mother's pouch. At 48 days of age, the young opossums detach
Water opossum
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SS President Hoover was an ocean liner built for the Dollar Steamship Lines. She was completed in 1930 and provided a trans-Pacific service between the US and the Far East. In 1937 she ran aground on an island off Formosa (now known as Taiwan) during a typhoon and was declared a total loss. She had a sister ship, , that was completed in 1931, was made a troopship in 1941 and was lost after striking a mine while attempting to enter the harbor at Espiritu Santo in 1942. History Building Dollar Lines ordered both the President Hoover and President Coolidge on 26 October 1929. The Newport News Shipbuilding and Drydock Company of Newport News, Virginia, USA, built the two ships, completing the Hoover in 1930 and Coolidge in 1931. They were the largest merchant ships built in the USA up to that time. First Lady Lou Henry Hoover launched and christened President Hoover on December 9, 1930. Each ship had turbo-electric transmission, with a pair of steam turbo generators generating current that powered propulsion motors on the twin propeller shafts. Westinghouse built the turbo generators and propulsion motors for President Coolidge but General Electric built the turbo generators and propulsion motors for President Hoover. 12 oil-fired Babcock & Wilcox high-pressure boilers supplied the steam for President Hoovers turbo-generators. The electric propulsion motors produced 26,500 shp at 133 RPM. President Hoovers accommodation was air conditioned and there was a 'phone in every cabin. There were swimming pools on deck, gymnasiums, a dance floor and Otis elevators. Décor was in contemporary Art Deco style and the First Class lounge was decorated with murals by the artist Frank Bergman of New York. Robert Dollar had bought his first ship in 1895, founded Dollar Lines in 1903 and was now 87 years old. On August 6, 1931, three days before President Hoover was launched, he toured her and declared "This ship is a wonder". Dollar lived until May 1932, just a few months after President Hoover and President Coolidge made their maiden voyages. Trans-Pacific service President Hoover and President Coolidge ran between San Francisco and Manila via Japan and China. The United States Postal Service subsidised them to carry mail, which helped Dollar to run the two ships at a profit. However, the Japanese invasion of Manchuria in 1931–32, the Japanese attack on the Great Wall in 1933 and the Japanese invasion of China starting in July 1937 all deterred US travel to the Far East, and Dollar Lines became increasingly unprofitable. Bombed in the Yangtze River After the Battle of Shanghai had broken out in August 1937, President Hoover was diverted from Hong Kong to evacuate US nationals from Shanghai. On 30 August the liner was moored in the Yangtze River, awaiting clearance to enter the Wusong River to reach the Port of Shanghai when, despite a -long US flag draped on her top deck abaft the bridge to identify her to aircraft as a neutral US ship, the Republic of China Air
SS President Hoover
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Harold Benjamin Finger (born February 18, 1924) is an American aeronautical nuclear engineer and the former head of the United States nuclear rocket program. He helped establish and lead the Space Nuclear Propulsion Office, a liaison organization between NASA and the Atomic Energy Commission to coordinate efforts to create a nuclear thermal rocket. Early life Harold Benjamin Finger was born in Brooklyn, New York City, on February 18, 1924, the son of Beny Finger and his wife Anna Perlmutter. He was called Harry by his family, friends and colleagues. His family moved to The Bronx when he was young. He attended Townsend Harris High School, from which he graduated in 1940. He then entered the City College of New York, from which he earned his Bachelor of Science degree in mechanical engineering in 1944. NACA During World War II, he had a deferment until graduation, after which he expected to be drafted. He applied for a commission in the United States Navy and to the National Advisory Committee for Aeronautics (NACA) He was accepted into the latter, and for NACA at its Aircraft Engine Research Laboratory in Cleveland, Ohio. He was nominally as a member of the United States Army Air Corps enlisted reserve, in May 1944. His work initially involved testing German and Japanese aircraft engines, but he became involved in the development of the axial-flow compressor for jet engines. The Aircraft Engine Research Laboratory was renamed the Lewis Flight Propulsion Laboratory after George W. Lewis on September 28, 1948. Finger married Arlene Karsh on June 11, 1949; they had three daughters. The following year, he was awarded a Master of Science degree in aeronautical engineering by the Case Institute of Technology. He became the head of the Axial Flow Compression Group at Lewis in 1952, and then Associate Chief of the Compressor Research Branch in 1954. Abe Silverstein, the director of Lewis, believed that nuclear propulsion would be important in the future. In 1956, he established a nuclear training school at Lewis. There were twenty four students, a mixture of new recruits and experienced engineers. Finger was one of those chosen to attend. Six of the students elected to not continue with nuclear technology; the rest were formed into three groups. Finger headed one, which studied nuclear rocket propulsion. Silverstein abolished Lewis' compressor and turbine division in March 1957. NASA On March 5, 1958, President Dwight D. Eisenhower announced his decision to create a new space agency, the National Aeronautics and Space Administration (NASA), which would absorb NACA. Silverstein moved to Washington, D.C., where he became the head of the Office of Space Flight Programs. Silverstein selected Finger to head NASA's nuclear projects. Responsibility for the nuclear thermal rocket project, Project Rover, was officially transferred from the United States Air Force (USAF) to NASA on October 1, 1958, the day NASA officially became operational and assumed responsibility for the US civilian space program. On August 29, 1960, NASA created the Space Nuclear Propulsion Office (SNPO) to oversee Project
Harold Finger
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Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from two Latin words: pro, meaning before or forward; and pellere, meaning to drive. A propulsion system consists of a source of mechanical power, and a propulsor (means of converting this power into propulsive force). Plucking a guitar string to induce a vibratory translation is technically a form of propulsion of the guitar string; this is not commonly depicted in this vocabulary, even though human muscles are considered to propel the fingertips. The motion of an object moving through a gravitational field is affected by the field, and within some frames of reference physicists speak of the gravitational field generating a force upon the object, but for deep theoretic reasons, physicists now consider the curved path of an object moving freely through space-time as shaped by gravity as a natural movement of the object, unaffected by a propulsive force (in this view, the falling apple is considered to be unpropelled, while the observer of the apple standing on the ground is considered to be propelled by the reactive force of the Earth's surface). Biological propulsion systems use an animal's muscles as the power source, and limbs such as wings, fins or legs as the propulsors. A technological system uses an engine or motor as the power source (commonly called a powerplant), and wheels and axles, propellers, or a propulsive nozzle to generate the force. Components such as clutches or gearboxes may be needed to connect the motor to axles, wheels, or propellers. A technological/biological system may use human, or trained animal, muscular work to power a mechanical device. Small objects, such as bullets, propelled at high speed are known as projectiles; larger objects propelled at high speed, often into ballistic flight, are known as rockets or missiles. Influencing rotational motion is also technically a form of propulsion, but in speech, an automotive mechanic might prefer to describe the hot gasses in an engine cylinder as propelling the piston (translational motion), which drives the crankshaft (rotational motion), the crankshaft then drives the wheels (rotational motion), and the wheels propel the car forward (translational motion). In common speech, propulsion is associated with spatial displacement more strongly than locally contained forms of motion, such as rotation or vibration. As another example, internal stresses in a rotating baseball cause the surface of the baseball to travel along a sinusoidal or helical trajectory, which would not happen in the absence of these interior forces; these forces meet the technical definition of propulsion from Newtonian mechanics, but are not commonly spoken of in this language. Vehicular propulsion Air propulsion An aircraft propulsion system generally consists of an aircraft engine and some means to generate thrust, such as a propeller or a propulsive nozzle. An aircraft propulsion system must achieve two things. First, the thrust
Propulsion
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Spacecraft flight dynamics is the application of mechanical dynamics to model how the external forces acting on a space vehicle or spacecraft determine its flight path. These forces are primarily of three types: propulsive force provided by the vehicle's engines; gravitational force exerted by the Earth and other celestial bodies; and aerodynamic lift and drag (when flying in the atmosphere of the Earth or other body, such as Mars or Venus). The principles of flight dynamics are used to model a vehicle's powered flight during launch from the Earth; a spacecraft's orbital flight; maneuvers to change orbit; translunar and interplanetary flight; launch from and landing on a celestial body, with or without an atmosphere; entry through the atmosphere of the Earth or other celestial body; and attitude control. They are generally programmed into a vehicle's inertial navigation systems, and monitored on the ground by a member of the flight controller team known in NASA as the flight dynamics officer, or in the European Space Agency as the spacecraft navigator. Flight dynamics depends on the disciplines of propulsion, aerodynamics, and astrodynamics (orbital mechanics and celestial mechanics). It cannot be reduced to simply attitude control; real spacecraft do not have steering wheels or tillers like airplanes or ships. Unlike the way fictional spaceships are portrayed, a spacecraft actually does not bank to turn in outer space, where its flight path depends strictly on the gravitational forces acting on it and the propulsive maneuvers applied. Basic principles A space vehicle's flight is determined by application of Newton's second law of motion: where F is the vector sum of all forces exerted on the vehicle, m is its current mass, and a is the acceleration vector, the instantaneous rate of change of velocity (v), which in turn is the instantaneous rate of change of displacement. Solving for a, acceleration equals the force sum divided by mass. Acceleration is integrated over time to get velocity, and velocity is in turn integrated to get position. Flight dynamics calculations are handled by computerized guidance systems aboard the vehicle; the status of the flight dynamics is monitored on the ground during powered maneuvers by a member of the flight controller team known in NASA's Human Spaceflight Center as the flight dynamics officer, or in the European Space Agency as the spacecraft navigator. For powered atmospheric flight, the three main forces which act on a vehicle are propulsive force, aerodynamic force, and gravitation. Other external forces such as centrifugal force, Coriolis force, and solar radiation pressure are generally insignificant due to the relatively short time of powered flight and small size of spacecraft, and may generally be neglected in simplified performance calculations. Propulsion The thrust of a rocket engine, in the general case of operation in an atmosphere, is approximated by: where, is the exhaust gas mass flow is the effective exhaust velocity (sometimes otherwise denoted as c in publications) is the effective jet velocity when pamb = pe is the flow area at nozzle exit plane (or the
Spacecraft flight dynamics
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Antimatter-catalyzed nuclear pulse propulsion (also antiproton-catalyzed nuclear pulse propulsion) is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel to initiate a nuclear chain reaction for propulsion when the fuel does not normally have a critical mass. Technically, the process is not a '"catalyzed'" reaction because anti-protons (antimatter) used to start the reaction are consumed; if they were present as a catalyst the particles would be unchanged by the process and used to initiate further reactions. Although antimatter particles may be produced by the reaction itself, they are not used to initiate or sustain chain reactions. Description Typical nuclear pulse propulsion has the downside that the minimal size of the engine is defined by the minimal size of the nuclear bombs used to create thrust, which is a function of the amount of critical mass required to initiate the reaction. A conventional thermonuclear bomb design consists of two parts: the primary, which is almost always based on plutonium, and a secondary using fusion fuel, which is normally deuterium in the form of lithium deuteride, and tritium (which is created during the reaction as lithium is transmuted to tritium). There is a minimal size for the primary (about 10 kilograms for plutonium-239) to achieve critical mass. More powerful devices scale up in size primarily through the addition of fusion fuel for the secondary. Of the two, the fusion fuel is much less expensive and gives off far fewer radioactive products, so from a cost and efficiency standpoint, larger bombs are much more efficient. However, using such large bombs for spacecraft propulsion demands much larger structures able to handle the stress. There is a tradeoff between the two demands. By injecting a small amount of antimatter into a subcritical mass of fuel (typically plutonium or uranium) fission of the fuel can be forced. An anti-proton has a negative electric charge, just like an electron, and can be captured in a similar way by a positively charged atomic nucleus. The initial configuration, however, is not stable and radiates energy as gamma rays. As a consequence, the anti-proton moves closer and closer to the nucleus until their quarks can interact, at which point the anti-proton and a proton are both annihilated. This reaction releases a tremendous amount of energy, of which some is released as gamma rays and some is transferred as kinetic energy to the nucleus, causing it to split (the fission reaction). The resulting shower of neutrons can cause the surrounding fuel to undergo rapid fission or even nuclear fusion. The lower limit of the device size is determined by anti-proton handling issues and fission reaction requirements, such as the structure used to contain and direct the blast. As such, unlike either the Project Orion-type propulsion system, which requires large numbers of nuclear explosive charges, or the various antimatter drives, which require impossibly expensive amounts of antimatter, antimatter-catalyzed nuclear pulse propulsion has intrinsic advantages. A conceptual design of an antimatter-catalyzed thermonuclear explosive physics
Antimatter-catalyzed nuclear pulse propulsion
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A robot fish is a type of bionic robot that has the shape and locomotion of a living fish. Most robot fish are designed to emulate living fish which use body-caudal fin (BCF) propulsion, and can be divided into three categories: single joint (SJ), multi-joint (MJ) and smart material-based "soft-body" design. Since the Massachusetts Institute of Technology first published research on them in 1989, there have been more than 400 articles published about robot fish. According to these reports, approximately 40 different types of robot fish have been built, with 30 designs having only the capability to flip and drift in water. The most important parts of researching and developing robot fish are advancing their control and navigation, enabling them to interact and "communicate" with their environment, making it possible for them to travel along a particular path, and to respond to commands to make their "fins" flap. Design The basic biomimetic robotic fish is made up of three parts: a streamlined head, a body, and a tail. The head is often made of a rigid plastic material (i.e. fiberglass) and contains all control units including a wireless communication module, batteries, and a signal processor. The body may be made of multiple jointed segments, which are connected by servomotors. Servomotors control the rotation angle of the joint. Some designs have pectoral fins fixed on both sides of the body to ensure stability in the water An oscillating caudal (tail) fin connected with joints and driven by a motor provides motive power. Design inspiration Engineers often focus on functional design. For example, designers attempt to create robots with flexible bodies (like real fish) that can exhibit undulatory motion. This kind of body enables the robot fish to swim similar to the way live fish swim, which can adapt and process a complicated environment. The first robot fish (MIT's RoboTuna) was designed to mimic the structure and dynamic properties of a Tuna. In an attempt to gain thrust and maneuvering forces, robot fish control systems are capable of controlling the body and caudal fin, giving them a wave-like motion. In order to control and analyze robotic fish movement, researchers study the shape, dynamic model and lateral movements of the robotic tail. One of the many tail shapes found on robot fish is lunate, or crescent shaped. Some studies show this kind of tail shape increases swimming speeds and creates a high-efficiency robot fish. The posterior tail creates thrust force, making it one of the most important parts of the robot fish. Living fish have powerful muscles that can generate lateral movements for locomotion while the head remains in a relatively motionless state. Thus, researchers have focused on tail kinematics when developing robot fish motion. Slender-body theory is often used when studying robot fish locomotion. The mean rate of work of the lateral movements is equal to the sum of the mean rate of work available for producing the mean thrust and the rate of shedding of kinetic energy of lateral fluid motions.
Robot fish
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Vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air/surface/water conditions, etc. Vehicle dynamics is a part of engineering primarily based on classical mechanics. It may be applied for motorized vehicles (such as automobiles), bicycles and motorcycles, aircraft, and watercraft. Factors affecting vehicle dynamics The aspects of a vehicle's design which affect the dynamics can be grouped into drivetrain and braking, suspension and steering, distribution of mass, aerodynamics and tires. Drivetrain and braking Automobile layout (i.e. location of engine and driven wheels) Powertrain Braking system Suspension and steering Some attributes relate to the geometry of the suspension, steering and chassis. These include: Ackermann steering geometry Axle track Camber angle Caster angle Ride height Roll center Scrub radius Steering ratio Toe Wheel alignment Wheelbase Distribution of mass Some attributes or aspects of vehicle dynamics are purely due to mass and its distribution. These include: Center of mass Moment of inertia Roll moment Sprung mass Unsprung mass Weight distribution Aerodynamics Some attributes or aspects of vehicle dynamics are purely aerodynamic. These include: Automobile drag coefficient Automotive aerodynamics Center of pressure Downforce Ground effect in cars Tires Some attributes or aspects of vehicle dynamics can be attributed directly to the tires. These include: Camber thrust Circle of forces Contact patch Cornering force Ground pressure Pacejka's Magic Formula Pneumatic trail Radial Force Variation Relaxation length Rolling resistance Self aligning torque Skid Slip angle Slip (vehicle dynamics) Spinout Steering ratio Tire load sensitivity Vehicle behaviours Some attributes or aspects of vehicle dynamics are purely dynamic. These include: Body flex Body roll Bump Steer Bundorf analysis Directional stability Critical speed Noise, vibration, and harshness Pitch Ride quality Roll Speed wobble Understeer, oversteer, lift-off oversteer, and fishtailing Weight transfer and load transfer Yaw Analysis and simulation The dynamic behavior of vehicles can be analysed in several different ways. This can be as straightforward as a simple spring mass system, through a three-degree of freedom (DoF) bicycle model, to a large degree of complexity using a multibody system simulation package such as MSC ADAMS or Modelica. As computers have gotten faster, and software user interfaces have improved, commercial packages such as CarSim have become widely used in industry for rapidly evaluating hundreds of test conditions much faster than real time. Vehicle models are often simulated with advanced controller designs provided as software in the loop (SIL) with controller design software such as Simulink, or with physical hardware in the loop (HIL). Vehicle motions are largely due to the shear forces generated between the tires and road, and therefore the tire model is an essential part of the math model. In current vehicle simulator models, the tire model is the weakest and most difficult part to simulate. The tire model must produce realistic shear forces during braking, acceleration, cornering, and combinations, on a range of surface conditions. Many models are in use. Most are semi-empirical, such as the Pacejka Magic Formula model. Racing
Vehicle dynamics
53769380
The webbed foot is a specialized limb with interdigital membranes (webbings) that aids in aquatic locomotion, present in a variety of tetrapod vertebrates. This adaptation is primarily found in semiaquatic species, and has convergently evolved many times across vertebrate taxa. It likely arose from mutations in developmental genes that normally cause tissue between the digits to apoptose. These mutations were beneficial to many semiaquatic animals because the increased surface area from the webbing allowed for more swimming propulsion and swimming efficiency, especially in surface swimmers. The webbed foot also has enabled other novel behaviors like escape responses and mating behaviors. A webbed foot may also be called a paddle to contrast it from a more hydrofoil-like flipper. Morphology A webbed foot has connecting tissue between the toes of the foot. Several distinct conditions can give rise to webbed feet, including interdigital webbing and syndactyly. The webbing can consist of membrane, skin, or other connective tissue and varies widely in different taxa. This modification significantly increases the surface area of the feet. One of the consequences of this modification in some species, specifically birds, is that the feet are a major location for heat loss. In birds, the legs utilize countercurrent heat exchange so that blood reaching the feet is already cooled by blood returning to the heart to minimize this effect. Webbed feet take on a variety of different shapes; in birds, the webbing can even be discontinuous, as seen in lobate-footed birds like grebes. However, one of the most common is the delta (Δ) or triangular shape seen in most waterfowl and frogs. This delta wing shape is a solution that has convergently evolved in many taxa, and is also used in aircraft to allow for high lift forces at high attack angles. This shape allows for the production of large forces during swimming through both drag-based and lift-based propulsion. Webbed feet are a compromise between aquatic and terrestrial locomotion. Aquatic control surfaces of non-piscine vertebrates may be paddles or hydrofoils. Paddles generate less lift than hydrofoils, and paddling is associated with drag-based control surfaces. The roughly triangular design of webbed feet, with a broad distal end, is specialized to increase propulsive efficiency by affecting a larger mass of water over generating increased lift. This is in contrast to a more hydrofoil-like flipper of many permanently aquatic animals. Evolution Development Webbed feet are the result of mutations in genes that normally cause interdigital tissue between the toes to apoptose. Apoptosis, or programmed cell death, in development is mediated by a variety of pathways, and normally causes the creation of digits by death of tissue separating the digits. Different vertebrate species with webbed feet have different mutations that disrupt this process, indicating that the structure arose independently in these lineages. In humans, syndactyly can arise from as many as nine unique subtypes with their own clinical, morphological, and genetic fingerprints. In addition, the same genetic mutations can underlie different phenotypic expressions of syndactyly. While these conditions are disorders in humans,
Webbed foot
140697
A torpedo tube is a cylindrical device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units (also referred to as torpedo launchers) installed aboard surface vessels. Deck-mounted torpedo launchers are usually designed for a specific type of torpedo, while submarine torpedo tubes are general-purpose launchers, and are often also capable of deploying mines and cruise missiles. Most modern launchers are standardized on a diameter for light torpedoes (deck mounted aboard ship) or a diameter for heavy torpedoes (underwater tubes), although other sizes of torpedo tube have been used: see Torpedo classes and diameters. Submarine torpedo tube A submarine torpedo tube is a more complex mechanism than a torpedo tube on a surface ship, because the tube has to accomplish the function of moving the torpedo from the normal atmospheric pressure within the submarine into the sea at the ambient pressure of the water around the submarine. Thus a submarine torpedo tube operates on the principle of an airlock. Torpedo tube operation The diagram illustrates the operation of a submarine torpedo tube. The diagram is somewhat simplified but does show the working of a submarine torpedo launch. A torpedo tube has a considerable number of interlocks for safety reasons. For example, an interlock prevents the breech door and muzzle door from opening at the same time. The submarine torpedo launch sequence is, in simplified form: Open the breech door in the torpedo room. Load the torpedo into the tube. Hook up the wire-guide connection and the torpedo power cable. Shut and lock the breech door. Turn on power to the torpedo. A minimum amount of time is required for torpedo warmup. Fire control programs are uploaded to the torpedo. Flood the torpedo tube. This may be done manually or automatically, from sea or from tanks, depending on the class of submarine. The tube must be vented during this process to allow for complete filling and eliminate air pockets which could escape to the surface or cause damage when firing. Open the equalizing valve to equalize pressure in the tube with ambient sea pressure. Open the muzzle door. If the tube is set up for Impulse Mode the slide valve will open with the muzzle door. If Swim Out Mode is selected, the slide valve remains closed. The slide valve allows water from the ejection pump to enter the tube. When the launch command is given and all interlocks are satisfied, the water ram operates, thrusting a large volume of water into the tube at high pressure, which ejects the torpedo from the tube with considerable force. Modern torpedoes have a safety mechanism that prevents activation of the torpedo unless the torpedo senses the required amount of G-force. The power cable is severed at launch. However, if a guidance wire is used, it remains connected through a drum of wire in the tube. Torpedo propulsion systems vary but electric torpedoes swim out of the tube on their own
Torpedo tube
16459
Jet Propulsion Laboratory (JPL) is a federally funded research and development center in La Cañada Flintridge, California, United States. Founded in 1936 by Caltech researchers, the laboratory is now owned and sponsored by the National Aeronautics and Space Administration (NASA) and administered and managed by the California Institute of Technology. The laboratory's primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating the NASA Deep Space Network. Among the laboratory's major active projects are the Mars 2020 mission, which includes the Perseverance rover; the Mars Science Laboratory mission, including the Curiosity rover; the Mars Reconnaissance Orbiter; the Juno spacecraft orbiting Jupiter; the SMAP satellite for earth surface soil moisture monitoring; the NuSTAR X-ray telescope; and the Psyche asteroid orbiter. It is also responsible for managing the JPL Small-Body Database, and provides physical data and lists of publications for all known small Solar System bodies. JPL's Space Flight Operations Facility and Twenty-Five-Foot Space Simulator are designated National Historic Landmarks. History JPL traces its beginnings to 1936 in the Guggenheim Aeronautical Laboratory at the California Institute of Technology (GALCIT) when the first set of rocket experiments were carried out in the Arroyo Seco. This initial venture involved Caltech graduate students Frank Malina, Qian Xuesen, Weld Arnold and Apollo M. O. Smith, along with Jack Parsons and Edward S. Forman, often referred to as the "Suicide Squad" due to the dangerous nature of their experiments. Together, they tested a small, alcohol-fueled motor to gather data for Malina's graduate thesis. Malina's thesis advisor was engineer/aerodynamicist Theodore von Kármán, who eventually secured U.S. Army financial support for this "GALCIT Rocket Project" in 1939. Rocketry beginnings In the early years of the project, work was primarily focused on the development of rocket technology. In 1941, Malina, Parsons, Forman, Martin Summerfield, and pilot Homer Bushey demonstrated the first jet-assisted takeoff (JATO) rockets to the Army. In 1943, von Kármán, Malina, Parsons, and Forman established the Aerojet Corporation to manufacture JATO rockets. The project took on the name Jet Propulsion Laboratory in November 1943, formally becoming an Army facility operated under contract by the university. In the same year, Qian and two of his colleagues drafted the first document to use the name Jet Propulsion Laboratory. In a NASA conference on the history of early rocketry, Malina wrote that the work of the JPL was "considered to include" the research carried out by the GALCIT Rocket Research Group from 1936 on. In 1944, Parsons was expelled due to his "unorthodox and unsafe working methods" following one of several FBI investigations into his involvement with the occult, drugs and sexual promiscuity. During JPL's Army years, the laboratory developed two significant deployed weapon systems, the MGM-5 Corporal and MGM-29 Sergeant intermediate-range ballistic missiles, marking the first US ballistic missiles developed at JPL. It also developed several other weapons system prototypes, such as the Loki anti-aircraft missile system, and the forerunner of the Aerobee sounding rocket.
Jet Propulsion Laboratory
949363
The Gepard-class frigates, Russian designation Project 11661, is a Russian class of frigates that were intended as successors to the earlier s and , and corvettes. The first unit of the class, Yastreb (Hawk), was laid down at the Zelenodol'sk Zavod shipyard at Tatarstan in 1991. She was launched in July 1993, after which she began fitting out; fitting was nearly completed by late 1995, when it was suspended due to lack of funds. Renamed Tatarstan, the ship was finally completed in July 2002, and became the flagship of the Caspian Flotilla. She has two sister ships, Albatross (renamed Dagestan), and Burevestnik (Storm Petrel), which was still under construction . Vietnam is the main operator of the class with its navy having commissioned 4 frigates - twice the size of Russia's Project 11661 inventory - and having plans to order at least 2 more. Design These vessels are capable of employing their weapons systems in conditions up to Sea State 5. The hull and superstructure are constructed primarily of steel, with some aluminium-magnesium being used in the upper superstructure(stealth technology). They are equipped with fin stabilizers and twin rudders, and can use either gas turbines or diesel for propulsion in a CODOG configuration. Gepard is Russian for cheetah. Service history In October 2015, Dagestan, in company with three other Russian Navy ships serving with the Caspian Flotilla, launched cruise missiles at targets in Syria. The missiles flew nearly over Iran and Iraq and struck targets in Raqqa and Aleppo provinces (controlled by the Islamic State) as well as Idlib province (controlled by the al-Qaeda-linked Nusra Front). Peshmerga forces (Kurdish armed forces located in northern Iraq) published a video allegedly depicting two cruise missiles mid-flight en route to Syria. Export The Gepard-class was designed from the outset as a lightweight, inexpensive export vessel. Russia offers three variants of the class to the market: Gepard 3.9: designed to search, track and fight against surface, underwater and air enemy independently and within task force, plant mine fields, provide protection and patrol of maritime state border and exclusive economic zone, perform combat missions, patrol service. Powered by gas-turbine engines with CODOG configuration. Fitted with two inclined quadruple launchers for eight Kh-35 anti-ship missiles with alternative options to be featured with VLS systems such as UKSK (for cruise missiles such as Club-N and Yakhont) and Shtil-1 air-defense system. Being the only exported variant with Vietnam being its first and only operator. Gepard 5.1: configured as an ocean-going patrol ship. Intended for patrolling territorial waters, helping in distress on the sea, environment protection, support to marine missions and flag demonstration in areas being of state interest. Can be featured with "heavier" weapons if necessary. Powered entirely by diesel engines with a two-shaft CODAD propulsion plant. Gepard 5.3: designed to search, track and fight against surface, underwater and air enemy independently and within task force, carry out convoy missions and patrol duty, guard maritime state border and economic zone. Featured with four quadruple launchers for sixteen Kh-35
Gepard-class frigate
1044906
A flipper is a broad, flattened limb adapted for aquatic locomotion. It refers to the fully webbed, swimming appendages of aquatic vertebrates that are not fish. In animals with two flippers, such as whales, the flipper refers solely to the forelimbs. In animals with four flippers, such as pinnipeds and sea turtles, one may distinguish fore- and hind-flippers, or pectoral flippers and pelvic flippers. Animals with flippers include penguins (whose flippers are also called wings), cetaceans (e.g., dolphins and whales), pinnipeds (e.g., walruses, earless and eared seals), sirenians (e.g., manatees and dugongs), and marine reptiles such as the sea turtles and the now-extinct plesiosaurs, mosasaurs, ichthyosaurs, and metriorhynchids. Usage of the terms "fin" and "flipper" is sometimes inconsistent, even in the scientific literature. However, the hydrodynamic control surfaces of fish are always referred to as "fins" and never "flippers". Tetrapod limbs which have evolved into fin-like structures are usually (but not always) called "flippers" rather than fins. The dorsal structure on cetaceans is called the "dorsal fin" and the large cetacean tails are referred to primarily as flukes but occasionally as "caudal fins"; neither of these structures are flippers. Some flippers are very efficient hydrofoils, analogous to wings (airfoils), used to propel and maneuver through the water with great speed and maneuverability (see Foil). Swimming appendages with the digits still apparent, as in the webbed forefeet of amphibious turtles and platypus, are considered paddles rather than flippers. Locomotion For all species of aquatic vertebrates, swimming performance depends upon the animal's control surfaces, which include flippers, flukes and fins. Flippers are used for different types of propulsion, control, and rotation. In cetaceans, they are primarily used for control while the fluke is used for propulsion. The evolution of flippers in penguins was at the expense of their flying capabilities, in spite of evolving from an auk-like ancestor that could 'fly' underwater as well in the air. Form constrains function, and the wings of diving flying species, such as the murre or cormorant have not developed into flippers. The flippers of penguins became thicker, denser and smaller while being modified for hydrodynamic properties. Hydrodynamics Cetacean flippers may be viewed as being analogous to modern engineered hydrofoils, which have hydrodynamic properties: lift coefficient, drag coefficient and efficiency. Flippers are one of the principal control surfaces of cetaceans (whales, dolphins and porpoises) due to their position in front of the center of mass, and their mobility which provides three degrees of freedom. Flippers on humpback whales (Megaptera novaeangliae) have non-smooth leading edges, yet demonstrate superior fluid dynamics to the characteristically smooth leading edges of artificial wings, turbines and other kinds of blades. The whale's surprising dexterity is due primarily to its non-conventional flippers, which have large, irregular looking bumps called tubercles across their leading edges. The tubercles break up the passage of water, maintaining even channels of the fast-moving water, limiting turbulence and providing greater maneuverability. The foreflippers used by the pinnipeds act as oscillatory hydrofoils. Both fore and hind flippers are used for
Flipper (anatomy)
26162908
The DRDO Anti-Tank Missile is a first generation wire-guided anti-tank guided missile (ATGM) developed in India by Defence Research and Development Laboratory (DRDL), a part of the Defence Research and Development Organisation (DRDO). It has a subsonic speed up to with a range of and carries a 106 mm high-explosive anti-tank (HEAT) warhead. Introduction In 1959, India began a feasibility study on a first generation ATGM. New General Staff Qualitative Requirements (GSQR) were issued and the task of preliminary study and wind testing was assigned to Department of Aeronautics and Institute of Science, Bangalore. Development In 1962, DRDO was granted to begin work on developing an anti-tank missile due to a conflict with China in Ladakh. It has a range of 500 meters to about 2 km. After the first aerodynamic design was completed, a full-scale model of the complete configuration was tested in a wind tunnel at Indian Institute of Science (IISc), Bangalore. There, the model was given force and momentum tests which were completed in 1961. Vibrating spoilers were used during these tests to determine control effectiveness. The ATM was designed to have a subsonic flight speed of about . In 1963, the entire design was reworked to hold a 106 mm HEAT warhead in the nose. Propulsion DRDL determined the propulsion motor requirement and designed the propulsion system. The motor was made of aluminium alloy. It had two compartments, one for the sustainer and one for the booster. Another part of DRDO, the Explosives Research & Development Laboratory (ERDL), made the propellant compositions and also developed the SUK black propulsion grains. Molybdenum inserts were used as sustainer. The booster grain had star type hole for very fast burn and the sustainer was cigarette burning type for constant thrust. Control and guidance The actuator and gyroscope were the main components of the control and guidance system of the missile. The actuators were spoiler type, (similar to Mosquito (missile)), which gave a response time of 10 milliseconds with a stay time varying from 80–20 and 20–80 milliseconds. The gyroscope developed for the missile had three degrees freedom. Testing The missile was test-fired near Imarat, a village on the outskirts of Hyderabad, India, which held the reliability order of 65%. The test trials were attended by Gen Bewoor, then Deputy Chief of Army Staff of the Indian Army. The missile was tested 16 times and hit its target 14 times. Two Indian army teams which were trained on European ATMs, Cobra and ENTAC, carried out the tests. These test revealed no significant difference between firing the European and indigenous ATMs. Work was still to be done on inhibition of the sustainer motor. Termination After waiting for more than 10 years with no results, in 1969 ATM project was terminated as the Indian Army revised its General Staff Qualitative Requirements (GSQR). The new GSQR extended the range of the missile from 1.6 km to 3 km. They also required the formerly man-portable missile to be able to mount and fire from
DRDO Anti Tank Missile
69634293
An active Brownian particle (ABP) is a model of self-propelled motion in a dissipative environment. It is a nonequilibrium generalization of a Brownian particle. The self-propulsion results from a force that acts on the particle's center of mass and points in the direction of an intrinsic body axis (the particle orientation). It is common to treat particles as spheres, though other shapes (such as rods) have also been studied. Both the center of mass and the direction of the propulsive force are subjected to white noise, which contributes a diffusive component to the overall dynamics. In its simplest version, the dynamics is overdamped and the propulsive force has constant magnitude, so that the magnitude of the velocity is likewise constant (speed-up to terminal velocity is instantaneous). The term active Brownian particle usually refers to this simple model and its straightforward extensions, though some authors have used it for more general self-propelled particle models. Equations of motion Mathematically, an active Brownian particle is described by its center of mass coordinates and a unit vector giving the orientation. In two dimensions, the orientation vector can be parameterized by the 2D polar angle , so that . The equations of motion in this case are the following stochastic differential equations: where with the 2×2 identity matrix. The terms and are translational and rotational white noise, which is understood as a heuristic representation of the Wiener process. Finally, is an external potential, is the mass, is the friction, is the magnitude of the self-propulsion velocity, and and are the translational and rotational diffusion coefficients. The dynamics can also be described in terms of a probability density function , which gives the probability, at time , of finding a particle at position and with orientation . By averaging over the stochastic trajectories from the equations of motion, can be shown to obey the following partial differential equation: Behavior For an isolated particle far from boundaries, the combination of diffusion and self-propulsion produces a stochastic (fluctuating) trajectory that appears ballistic over short length scales and diffusive over large length scales. The transition from ballistic to diffusive motion is defined by a characteristic length , called the persistence length. In the presence of boundaries or other particles, more complex behavior is possible. Even in the absence of attractive forces, particles tend to accumulate at boundaries. Obstacles placed within a bath of active Brownian particles can induce long-range density variations and nonzero currents in steady state. Sufficiently concentrated suspensions of active Brownian particles phase separate into a dense and dilute regions. The particles' motility drives a positive feedback loop, in which particles collide and hinder each other's motion, leading to further collisions and particle accumulation. At a coarse-grained level, a particle's effective self-propulsion velocity decreases with increased density, which promotes clustering. In the more general context of self-propelled particle models, this behavior is known as motility-induced phase separation. It is a type of athermal phase separation because it occurs even if the particles are spheres with hard-core (purely
Active Brownian particle
3839064
The behavioural despair test (or Porsolt forced swimming test) is a test, centered on a rodent's response to the threat of drowning, whose result has been interpreted as measuring susceptibility to negative mood. It is commonly used to measure the effectiveness of antidepressants, although significant criticisms of its interpretation have been made. Method Animals are subjected to two trials during which they are forced to swim in an acrylic glass cylinder filled with water, and from which they cannot escape. The first trial lasts 15 minutes. Then, after 24-hours, a second trial is performed that lasts 5 minutes. The time that the test animal spends in the second trial without making any movements beyond those required to keep its head above water is measured. This immobility time is decreased by various types of antidepressants and also by electroconvulsive shock. Another common variant of this behavioural test specifically used for mice is conducted only for one trial and lasts six minutes. Modern implementations of the test score swimming and climbing behaviours separately, because swimming behaviour has been shown to be increased by selective serotonin reuptake inhibitors, while climbing behaviour is increased by selective norepinephrine reuptake inhibitors such as desipramine and maprotiline. Controversy in interpretation Classically, immobility in the second test has been interpreted as a behavioural correlate of negative mood, representing a kind of hopelessness in the animal. Rodents given antidepressants swim harder and longer than controls (which forms the basis for claims of the test's validity). However, there is some debate between scientists whether increased immobility instead demonstrates learning or habituation, and would therefore be a positive behavioural adaptation: the animal is less fearful because it is now familiar with the environment of the test. This interpretation is supported by the fact that even rats who are first put into a container from which they can escape (and therefore do not experience despair) show reduced mobility in the second test. Some pharmacological compounds that influence motor movement, like stimulants and sedatives, may cause animals to swim for different amounts of time that are unrelated to the antidepressant properties of the compound. Researchers need to assess locomotor activity in the animal's homecage or by a locomotor test. If locomotion is altered compared to controls then other animal antidepressant models should be used. The term "behavioural despair test" bears an anthropomorphic connotation and is a somewhat subjective description as it is uncertain whether the test reliably gauges mood or despair. Strictly speaking, the descriptive term "forced swimming test" is preferred by researchers. The use of forced swimming tests is criticised by animal rights groups, notably PETA. See also Animal models of depression Learned helplessness Open field (animal test) Tail suspension test References Animal testing techniques Psychology experiments
Behavioural despair test
39135116
Various marine animals are capable of aerial locomotion, i.e., jumping out of the water and moving through air. Some possible reasons for this behavior are hunting, escaping from predators, and saving energy for swimming or breathing. Some of the jumping behaviors initiate gliding and taxiing in air, while some of them end up falling back to water. Penetrating water surface The speed of motion in air is faster than in water because of drag force. The drag force is proportional to density of the fluid. The animal jumping out of water will feel almost no drag, since the air density is 1,000 times less than water density. Usually animals gain thrust for the jumping as how they lift themselves underwater. Some of them are group behavior. Mechanism Jet propulsion Jet propulsion generates thrust and momentum by shooting out water jets. Flying squid is known for their behavior of leaping out of the water. Ommastrephinae and Todarodinae are two subfamilies of squids under the family of Ommastrephidae. They utilize jet propulsion to jump out of water as they do underwater, including Japanese flying squid.., Humboldt squid, Neon flying squid, sevenstar flying squid, and Wellington flying squid. Squid flight may be thought to reduce the cost of migration. The acceleration of Sthenoteuthis pteropus in air is 265 body lengths/s2 (24.5 m/s2), which is found to exceed that in water (79 body lengths/s2). Tail beating The fish approach the water surface at high speed (about 10 m/s in large fish; 20-30 body lengths/s) with their lateral fins furled against the body. They get accelerated by beating their tails rapidly, and break through the water surface at a shallow angle to the horizontal. Four fish in ray-finned fish family (Beloniformes) and salmon have this jumping behavior. The ray-finned fish includes needlefish, flyingfish, halfbeak, and sauries. Salmon jump out waterfalls during upstream spawning migrations. C-start C-start is escape reflex employed by fish. The fish move upward by curving their slender body as a letter C. Most of the fish jump out of water by C-start. Freshwater butterflyfish jumps out of water by curving its body. The fish is known for its enlarged pectoral fins but it falls back to water instead of gliding. Freshwater hatchetfish exhibits a ballistic aerial path. Porpoising Porpoising is high-speed swimming close to water surface with many leaving and re-entering the water nose-first. Dolphin, Penguin, and Seal porpoise in the wild. Dolphin saves energy at high speed porpoising. Penguin porpoises in group for long-distance traveling. Seal porpoises as group play Other The mechanisms and jumping patterns of some aquatic animals are not clear. Mobula penetrates sea surface by many photo evidences. Great white shark attacks seals near water surface at Seal Island in South Africa See also Tradeoffs for locomotion in air and water Flying and gliding animals The Flying Mobulas of the Sea of Cortez References Animal locomotion
Aerial locomotion in marine animals
13108497
Myomeres are blocks of skeletal muscle tissue arranged in sequence, commonly found in aquatic chordates. Myomeres are separated from adjacent myomeres by connective fascia (myosepta) and most easily seen in larval fishes or in the olm. Myomere counts are sometimes used for identifying specimens, since their number corresponds to the number of vertebrae in the adults. Location varies, with some species containing these only near the tails, while some have them located near the scapular or pelvic girdles. Depending on the species, myomeres could be arranged in an epaxial or hypaxial manner. Hypaxial refers to ventral muscles and related structures while epaxial refers to more dorsal muscles. The horizontal septum divides these two regions in vertebrates from cyclostomes to gnathostomes. In terrestrial chordates, the myomeres become fused as well as indistinct, due to the disappearance of myosepta. Shape The shape of myomeres varies by species. Myomeres are commonly zig-zag, "V" (lancelets), "W" (fishes), or straight (tetrapods)– shaped muscle fibers. Generally, cyclostome myomeres are arranged in vertical strips while those of jawed fishes are folded in a complex matter due to swimming capability evolution. Specifically, myomeres of elasmobranchs and eels are W-shaped. Contrastingly, myomeres of tetrapods run vertically and do not display complex folding. Another species with simply-lain myomeres are mudpuppies. Myomeres overlap each other in succession, meaning myomere activation also allows neighboring myomeres to activate. Myomeres are made up of myoglobin-rich dark muscle as well as white muscle. Dark muscle, generally, functions as slow-twitch muscle fibers while white muscle is composed of fast-twitch fibers. Function Specifically, three types of myomeres in fish-like chordates include amphioxine (lancelet), cyclostomine (jawless fish), and gnathostomine (jawed fish). A common function shared by all of these is that they function to flex the body laterally into concavity to provide force for locomotion. Since myomeres are composed of multinucleated myofibers (contractile cells), force can be generated via muscle contraction that gets transmitted by the intricate connective tissue (myosepta) network. Function in fishes The folded shape of each myomere as V- or W-shaped extends over various axial segments, allowing fibers control over a large amount of the body. Specifically, myomeres are overlapping cones bound by connective tissue. Myomeres compose most of the lateral musculature and provide propulsive force to travel along the line of travel. In this sense, they cause flexion to either side in order to produce locomotor force. Myomeres attach to centra of vertebrae, and neural and haemal spines. Further, myomeres of fish are divided by a horizontal septum into dorsal (epaxial) and ventral (hypaxial) sections as mentioned in previous paragraphs. Further, spinal nerves pass into each myomere. There are different variations of myomere activation depending on the type of swimming or movement. For example, high loading situations such as fast-starts and turning require almost maximal myomere activation in teleost fish. Further, if swim speeds are lower and movement is in one plane, there is less activation of myomeres. Further, research has discovered that fish are able to spatially restrict axial myomeres during different swimming
Myomere
56834712
The Asahi class of destroyers is a class of warships of the Japan Maritime Self-Defense Force. The Ashai is largely based on the Akizuki-class destroyer; While the Akizuki-class specialized in anti-air warfare, the Asahi-class was designed to specialize in anti-submarine warfare. The design was initially designated "25DD", referring to a date on the Japanese calendar, specifically the 25th fiscal year of the Heisei period (2013), the year that procurement of the class began. The lead ship, Asahi, is the third ship to hold the name after the Asahi-class destroyer escort lent from the United States Navy in 1955, and the Imperial Japanese battleship. The second ship of the class, Shiranui, is the third ship to hold the name after the Murakumo and Kagerō-class destroyers. Development The procurement of the destroyer began in 2013 in response to the reduction in the number of destroyers (namely the ) within the JMSDF. The two major characteristics of this destroyer is its bigger emphasis on anti-submarine warfare and the adoption of the COGLAG (combined gas turbine electric and gas turbine: a modification of the combined gas and gas propulsion system employing electric propulsion system for low-speed cruising) propulsion system. A second destroyer was procured a year later. Design The Asahi class is based on the existing to reduce acquisition cost and allow future development and growth. Unlike the Akizuki class (which focuses on anti-aircraft warfare) the Asahi class focuses on anti-submarine warfare. Features The Asahi class is the first Japanese warship to be equipped with a COGLAG propulsion system. This allows the destroyer to be more fuel efficient than previous warships. Another unique feature about this destroyer is the usage of a GaN-AESA (gallium nitride - active electronically scanned array) Multifunction Radar. The Asahi class is the second Japanese class of warship to be outfitted with this technology (the Akizuki class was the first). The destroyer's radar is based on the FCS-3A radar used for the Akizuki class and uses gallium nitride to improve performance. In radar technology, gallium nitride offers a number of advantages over the traditionally used gallium arsenide (GaA). These advantages include higher power density, efficiency, thermal spreading and frequency coverage. This in turn allows the GaN chip to be smaller than their GaA counterpart, thus reducing cost and increasing overall cost effectiveness. Ships in the class References
Asahi-class destroyer
51708180
Simone Arrigoni (born in Rome, Italy, on 4 September 1973) is an Italian free-diver. He holds multiple free-diving world records. He is an ActionAid Ambassador and Honorary Member of the Centro Studi Cetacei, a non-profit Italian association that is concerned with the study and rescue of marine mammals and reptiles since 1986. Free-diving Since 2008, Arrigoni has collaborated with biologists and students at Zoomarine Italia to carry on research projects on the study of free-diving and the comparative physiology of humans and dolphins. New disciplines He opened two new specialties of dynamic apnea: Horizontal Free Immersion, devised by Arrigoni in 2009 to allow disabled persons to play this aquatic sport, in which the freediver covers a horizontal distance pulling on a rope; Dolphin's Breath, which consists of freediving with monofin along a horizontal distance of predetermined length, periodically resurfacing to take a single breath of 1 second, and aiming at taking as few breaths as possible during the declared distance. The Dolphin's Breath was inaugurated by Arrigoni to disseminate two important slogans: "Mind the dolphins", to raise public awareness to protect marine mammals and their environment, and "Never alone", to remind people to never practice freediving alone for safety reasons, following the example given by dolphins which live and swim in a group, always helping each other in case of difficulty. World records Arrigoni set many world records: Dynamic freedive without fins in sea, 60 mt, Porto Santo Stefano, Italy, November 9, 2003. Dynamic freedive without fins under ice, 30 mt, at the 19th Stage of Diving Under Ice A.N.I.S., Lavarone, Italy, January 31, 2004. Dynamic freedive without fins in sea, 83 mt, Giochi del Mare, Balestrate, Italy, June 17, 2004. Dynamic freedive without fins in lake, 70 mt, Bracciano, Italy, June 7, 2005. Dynamic freedive without fins under ice, 41 mt, at the 21st Stage of Diving Under Ice A.N.I.S, Lavarone, Italy, February 4, 2006. Dynamic freedive with DPV (Dive Propulsion Vehicle) in sea, 231 mt, Giochi del Mare, Formia, Italy, June 25, 2007. Dynamic freedive with DPV (Diver propulsion vehicle) in lake, 381 mt, Bracciano, Italy, June 2, 2008. Freedive pushed by two dolphins, distance of 9 Zoomarine's swimming pools length (estimated of about 450 mt), Zoomarine, Torvaianica, Italy, May 17, 2009. Horizontal Free Immersion in sea, 101 mt, Giochi del Mare, Formia, Italy, June 17, 2009. Freedive pushed by two dolphins, 12 underwater loops, Zoomarine, Torvaianica, Italy, May 27, 2010. Freedive pushed by two dolphins, 13 underwater loops, Zoomarine, Torvaianica, Italy, May 19, 2011. Freedive pushed by two dolphins, 14 underwater loops, Zoomarine, Torvaianica, Italy, May 23, 2013. Dynamic freedive with DPV (Flyboard) in sea, 500 mt, Tropea, Italy, September 30, 2013. Freedive pushed by two dolphins, 15 underwater loops, Zoomarine, Torvaianica, Italy, May 22, 2014. Freedive pushed by one dolphin, 7 underwater loops, Zoomarine, Torvaianica, Italy, May 28, 2015. Dolphin's Breath with monofin in sea, 1 km with 95 single breaths (total time 23'30" with 1'35" of breathing), Giochi del Mare, Santa Marinella, Italy, June 8,
Simone Arrigoni
7621913
James Robert Thompson Jr. (March 6, 1936 – November 7, 2017), known as J.R. Thompson, was the fifth director of the NASA Marshall Space Flight Center located in Huntsville, Alabama. He served as director from September 29, 1986, to July 6, 1989. Thompson also served as NASA's deputy director from July 6, 1989, to November 8, 1991. Early life and education Born in Greenville, South Carolina, in 1936, Thompson graduated from Druid Hills High School in Atlanta in 1954. He was awarded a Bachelor of Science degree in aeronautical engineering from the Georgia Institute of Technology in 1958 and a Master of Science degree in mechanical engineering from the University of Florida in 1963. He has completed all course work at the University of Alabama toward a Ph.D. in fluid mechanics. Career Mr. Thompson served as a lieutenant in the U.S. Navy from 1958 to 1960 and was stationed at Green Cove Springs, Florida, as an administrative officer in the Atlantic Fleet. Mr. Thompson began his professional career in 1960 as a development engineer with Pratt and Whitney Aircraft in West Palm Beach, Florida. Mr. Thompson spent 20 years with NASA at the Marshall Space Flight Center in various positions, including associate director for engineering in the Science and Engineering Directorate and as manager of the Space Shuttle Main Engine Project in the Shuttle Projects Office. He joined the research and development team at the Marshall Center in 1963 as a liquid propulsion system engineer responsible for component design and performance analysis associated with the J-2 engine system on the Saturn Launch Vehicle. In 1966 he joined the Space Engine Section in the former Propulsion and Vehicle Engineering Laboratory at Marshall and became chief of the section in 1968. In that capacity, he was responsible for the design and test evaluation of auxiliary space engine propulsion systems for the Saturn Launch Vehicle and experimental small interplanetary propulsion systems. In 1969, Thompson transferred to Marshall's Astronautics Laboratory where he served as chief of the Man/Systems Integration Branch from 1969 to 1974. In September 1974, he was named manager of the Main Engine Projects Office at the Marshall Space Flight Center. In that position he was responsible for the development and operation of the most advanced liquid propulsion rocket engine ever developed. He served in that position almost from the beginning of early development testing on the Shuttle main engine through the initial Shuttle flights. In February 1982, Thompson was named associate director for engineering in the Marshall Science and Engineering Directorate. In that position, he was responsible for planning and executing the engineering overview, analysis, evaluation and support for all Marshall Center projects that were in the hardware development stage. He served three years as deputy director for technical operations at Princeton University's Plasma Physics Laboratory in Princeton, New Jersey. From March to June 1986, he was vice-chair of the NASA task force inquiring into the cause of the Space Shuttle Challenger accident. In that capacity, he headed the day-to-day operations
James R. Thompson Jr.