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patrickfleith

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Astro-mcqa

like 3

A probe is leaving the vicinity of Earth to fly to Mercury. Where will the solar panels generate the most power?

['In the vicinity of Earth.', 'Mid-flight from the Earth to Mercury.', 'In the vicinity of Mercury.', 'The distance to the Sun does not matter.']

[0, 0, 1, 0]

The solar irradiance decreases with the square of the distance to the Sun. Closer objects will receive more solar flux, thus more power is generated in the vicinity of Mercury than in the vicinity of Earth.

04ac75a0-ba3b-4c49-bf33-8105794ad710

The Earth receives an almost constant flux from the Sun of S = 1361 W/m^2. Which of the following is correct?

['All the energy received is funnelled to the core of the Earth to keep it at a constant temperature.', 'The Earth reflects most of the energy received and is kept in its thermal equilibrium by the heat source in its core.', 'The Earth is in constant shadow due to the multitude of satellites that orbit, such that it is in thermal equilibrium.', 'The Earth is in thermal equilibrium because some of the heat received is reflected back to space and the Earth radiates away energy, mostly in the IR.']

[0, 0, 0, 1]

There is an Earth energy budget. The input of energy are the Sun irradiance and the internal energy provided by the molten core. Some of the energy of the Sun is immediately reflected off the surface (via the albedo coefficient) and another output is the black body radiation of the Earth that peaks in the IR.

a59daf71-d948-4d60-b7a4-ace8e86205b3

The exterior of a satellite must be covered with a coating. What would be the best choice such that the temperature of the satellite is the lowest possible?

['Gold (alpha = 0.299, epsilon = 0.023)', 'White Epoxy (alpha = 0.248, epsilon = 0.924)', 'Titanium (alpha = 0.448, epsilon = 0.129)', 'Aluminum (alpha = 0.379, epsilon = 0.0346)']

[0, 1, 0, 0]

The best coating is the one that has the lowest alpha/epsilon ratio, because alpha describes the ability of the material to absorb heat while epsilon describes the capacity to radiate heat away. Among the proposed materials white epoxy is the best choice here. It has an alpha/epsilon ratio of about 0.27.

2afb1154-4608-47bd-9176-2b3503a1e8a6

Which modulation method can have a combination of 2 bits per symbol, a code rate of 0.5 and a spectral efficiency of about 1.0

['BPSK', 'QPSK', '8-PSK', '16-PSK']

[0, 1, 0, 0]

caf7a503-ce34-4d2e-a11a-a8eec2b04dbc

Which of the following statements are true about Precipitation Losses for Communication Link Analysis?

['precipitation losses attenuates RF signals by absorption', 'precipitation losses attenuates RF signals by scattering (depolarization)', 'Geographic databases of rainfall are needed for link analysis', 'precipitation losses are inversely proportional to the humidity in the atmosphere']

[1, 1, 1, 0]

Precipitation in the form of rain and wet snow attenuates RF signals through both absorption and scattering (depolarization). Precipitation-induced losses are dependent upon the product of a rate-dependent attenuation coefficient and the path length that the RF signals are required to traverse through rainfall regions within the atmosphere. Because losses are a function of the concentration of water in the atmosphere, precipitation-induced losses are heavily dependent upon a geographic and seasonal variation in weather. To provide a means for predicting rain precipitation effects, the ITU has created a geographic database of rainfall rates. This helps for link analysis.

61719260-46e9-444f-875e-8ea04e07f2bf

Which of the following influence the total power at the receive amplifier in communication link analyses?

['EIRP, the Equivalent Isotropic Radiated Power', 'mu, the Standard gravitational parameter', 'Ls, the Free-Space Losses', 'Lin, the input losses to the receiver', 'Ltx, the transmitter pointing losses', 'Na, the avogadro number']

[1, 0, 1, 1, 1, 0]

The total power at the receive amplifier can be expressed as C = EIRP + Gr - Ls - Latm - Lprec - Lin - Ltx - Lrx where EIRP is the Equivalent Isotropic Radiated Power, Gr is the gain of the receive antenna, Ls are the free-space losses, Latm and Lprec are the losses due to the atmosphere and precipitation, Lin the input losses to the receiver, Ltx the transmitter pointing losses, and Lrx the depointing losses of the receiver. The standard gravitational parameter has to do with orbital mechanics but not with communication link analysis and the avogadro number is used in chemistry, not in this context.

8a4c5031-a489-4d16-95b6-1049aa4806a3

In spacecraft link analysis which is the name used to refer to the signal transmitted from end users (for instance military troops) to the satellite?

['Forward uplink', 'Forward downlink', 'Return downlink', 'Return uplink']

[0, 0, 0, 1]

Forward communications links carry information toward user terminals, while return communications links carry information away from user terminals. Both forward and return links include uplinks and downlinks

2af4081d-5cf9-4a96-8177-f47711c45929

What does an engineer means when she say that "the link closes" in communication link analysis?

['The communication is finished and there are no more signal passing through the communication chain', 'The difference between the power-to-noise ratio and the detection threshold is positive', 'The difference between the power-to-noise ratio and the detection threshold is negative', "The energy received by the receiving antenna is strictly equal to the emitted energy (outputting the emitter's amplifier)", 'The link margin is negative']

[0, 1, 0, 0, 0]

The difference between the power-to-noise ratio and tabulated detection thresholds refer to a parameter called the link margin. When the link margin is positive, the received signal can be detected, and the link is said to "close". When it is negative however the signal cannot be detected and the link does not close.

a82da0e7-861e-420a-9cec-97be967adbc0

Which satellite band in the electromagnetic spectrum correspond to the highest frequencies?

['C-band', 'V-band', 'Ka-band', 'Q-band']

[0, 1, 0, 0]

V-band, mostly used for inter-satellite links uses frequency between 40 GHz and 75 GHz, then Q-band (30-40 GHz), then are Ka-band (18 to 30 GHz). C-band are of much lower frequencies, in the range of 4 to 7 GHz.

2e40b8b7-9830-4de0-b220-d77ad8c90abf

Which of the following satellite band is associated with its correct frequency range?

['Ka-band (18 to 30 GHz)', 'Ku-band (11 to 18 GHz)', 'S-band (7 to 11 GHz)', 'C-band (4 to 7 GHz)', 'Q-band (2 to 4 GHz)', 'V-band (1 to 2 Gz)']

[1, 1, 0, 1, 0, 0]

S-band frequencies are within 2 to 4 GHz, Q-band frequencies are within 30 to 40 GHz (much higher than those reported), and V-band are even higher frequencies, above 40 GHz. It is L-band which correspond to frequencies between 1 and 2 GHz.

e55ec36c-b9b5-45fe-8136-5d52273b54bd

True or False: an electromagnetic wave to that is RHCP means it is right-handed circular polarised and the electric field vector rotates anticlockwise as viewed from the direction of propagation?

['True', 'False']

[0, 1]

It False because RHCP means it is right-handed circular polarised and the electric field vector rotates clockwise (not anticlockwise) as viewed from the direction of propagation.

c2afbc6a-6128-49e9-b339-1ed9933da5a0

Why are Decibels used for communication links analyses?

['In hommage of George Mikari Decibels, the inventor of the mechanical speaker', 'This is a standard introduced by German scientist in Huntsville, Alabama, during Rocket Engine Fire test and was kept for legacy purpose and now introduced in the ECSS', 'Because link analyses involves calculations with numbers that may differ by many orders of magnitude, decibel is simpler, faster and less error-prone.', 'Because of Aristote']

[0, 0, 1, 0]

c41b75d1-8c13-49d1-ab68-ddf74eb73d52

What is the decibel equivalent of a 135 W amplifier output power relative to a 1 W reference?

['16.0', '18.2', '21.3', '23.4']

[0, 0, 1, 0]

The power in Decibels is given by P(dB) = 10 * LOG10( P / Pref ) = 10 * LOG10( 135 / 1 ) = 21.3

7aec6699-a608-4ed4-8140-446f0d5117dd

How do you express the antenna gain G as a function of the antenna directivity D and various losses L?

['G = D / L', 'G = D^2 / L', 'G = (D - L) / L', 'G = D - L']

[0, 0, 0, 1]

The total amplification factor of an antenna is given by its gain G, a value that includes both the focusing effect of the antenna (directivity D), which is a mesure of the antenna's ability to concentrate energy in a given direction, and various losses (including ohmic transmission-line losses, L for example). The formula is G = D - L

d1553f22-46fe-4dd8-9c35-a1df88727d49

What does A refer to in the formula G = etha * (4*pi / lambda^2 ) * A for communication link analyses

['A relates to the absorptivity of the emitting medium (dimensionless)', 'A relates to the physical size of the antenna aperture (m^2)', 'A to the antenna volume (m^3)']

[0, 1, 0]

604dfbb9-035f-4144-968e-4fc8259362e6

How do you compute theta (in degrees), the half-power beamwidth in link analyses?

['You cannot, you need to measure it', 'Theta = frequency / Diameter', 'Theta = - k*frequency, k is a tablulated constant', 'Theta = 21 / (frequency * Diameter)']

[0, 0, 0, 1]

883be593-9c9c-4437-a718-a0699882cc4c

Which is a major contribution to the antenna pointing error on-board satellite?

['thermal distortions', 'atmospheric residual drag', 'fixed misalignment']

[1, 0, 0]

Atmospheric drag is negligible and fixed misalignment is usually mitigated on-ground and static. However, a source for variable pointing error is related to thermal distortion that results from variable heating of different antenna and spacecraft structures, changing with as the orientation of the satellite and its antennas changes with respect to the Sun, Earth, and other satellite structures like solar panels and other antennas?

b774f04e-e3a3-43a1-ab0b-d9bf87639636

What does typical design allow for maximum satellite antennas pointing errors?

['Usually up to 50% of the beamwidth because it is sized to account for that loss', 'Usually around 10% of the beamwidth, so 0.1 degree for 1 degree beamwidth', 'Usually maximum 1% of the beamwidth, because beyond 1% the power-to-noise ratio decays exponentially minus infinity']

[0, 1, 0]

d7b25114-55fc-4143-bb47-9196a2a31f46

Who is not a European Astronaut?

['Thomas Pesquet', 'Christina Koch', 'Jeremy Hansen', 'Samantha Cristoforetti']

[0, 1, 1, 0]

7b251f74-511d-4057-8ed3-decd500f6bb6

What is the key difference between a jet engine and a liquid rocket engine?

['The jet engine is in general more expensive', 'The liquid rocket engine has to carry the oxidizer', 'The jet engine produce a long flamme tail after combustion']

[0, 1, 0]

The difference between a jet engine and a rocket engine, the jet engine only needs to carry its own fuel. A rocket, on the other hand, has to carry not only its own fuel but also the oxidizer, which in most cases is oxygen, either a compressed gas or liquid oxygen.

ae4e517f-c4a6-440c-98ff-c3d8d11faf09

How do satellite communication missions usually cover irregular areas such as the United States, without providing bandwidth to unwanted areas (oceans, prohibited areas)?

['Increasing satellite altitude', 'Utilising higher frequency bands', 'Encrypting the signal', 'Using shaped beam reflector antennas']

[0, 0, 0, 1]

Increasing the altitude would actually broaden the signal. Higher frequency bandas can offer more focused beams, but don't inherently prevent signal spill-over into unwanted areas. The key is the shape and direction of the beam, not the frequency. Finally, encrypting the signal does not prevent it from being broadcast over unwanted area, it only controls who can access the content of the signal.

c2a98060-6a75-4353-9d4a-2e157218c1d0

Assuming that D_ideal is the ideal antenna maximum directivity and A_theta is the coverage area in deg^2: Which of the following is a valid formula expressing the maximum directivity achievable for an ideal antenna that covers a small solid angle?

['D_ideal = 10 * log (A_theta)', 'D_ideal = exp(-A_theta)', 'D_ideal = A_theta / log(A_theta)', 'D_ideal = 46.15 - 10 * log(A_theta)']

[0, 0, 0, 1]

This provides a first level approximation for the link equation.

2a970ab4-5fd5-4e03-8e66-abaa2094b2cf

In space communication link analyses, the ideal directivity calculations do not include antenna radiated efficiency, which is a measure of the power being radiated outside of the desired coverage area. What is the typical range of antenna efficiencies to adjust the ideal directivity?

['20 to 40%', '55 to 75%', '80 to 99%', '98 to 99.5%']

[0, 1, 0, 0]

33c67e43-0041-4b8f-b867-37165c71c612

For ground or satellite antennas, which of the following are typical contributing components to the noise temperature?

["noise temperature that originates from the thermally radiated energy of objects that appear within the antenna's field of view", 'noise temperature that originates from the temperature of the antenna feed structure and transmission losses within the antenna and feed assembly itself', 'noise temperature that originates high energy ionizing particles deposited energy hitting the antenna structure', 'noise temperature that originates from the delta-phi (smalled boresight angle possible) product with the Earth reflected magnetic field when crossing of the south atlantic anomaly (SAA)']

[1, 1, 0, 0]

noise temperature that originates high energy ionising particles deposited energy hitting the antenna structure is negligible and the following "noise temperature that originates from the delta-phi (smallest bore-sight angle possible) product with the Earth reflected magnetic field when crossing of the South Atlantic Anomaly (SAA)" is not a concept used or reference in space mission engineering.

c41bef86-8e11-4f1d-a082-abbcecf64bd4

What are realistic mission objectives for a missions to Mars?

['ISRU Technology Demonstration', "Geological and topological study to understand the historical Mars-Earth collision which led to the creation of Earth's Moon.", 'Oild fields scoutting for future super tanker missions', 'Search for scientific evidence for past life on Mars']

[1, 0, 0, 1]

815136a9-3969-44c6-87d5-8bcea3f9517c

How long would a typical human crewed mission to Mars last (only the duration of the trip to reach Mars) for conjunction-type missions?

['3 to 4 months', '6 to 9 months', '3 to 4 years', 'more than 7 years']

[0, 1, 0, 0]

cc48db84-1b81-4670-a195-076dee267592

How are the two types chemical compounds of bipropellant propulsion systems called?

['Igniter and fuel', 'igniter and oxidizer', 'fuel and oxidizer']

[0, 0, 1]

73bf0237-afac-4dd9-a330-d8fcb3580379

Which of the following rocket engine(s) is / were manufactured by "Aerojet" ?

['MONARC-445', 'MR-111C', 'CHT-20']

[0, 1, 0]

The MR-111C is a flight proven monopropellant hydrazine thruster.

64fc0fa7-43af-41d6-b8c4-268ba0c928c8

Having stages in space launchers is advantageous because it disposes the the mass of the expended stage (tank, engine, etc...). But are there single stage launchers that are operational as of today in 2024 capable of launching a payload to Low Earth Orbit?

['Yes', 'No']

[0, 1]

41456ac5-fe9b-4178-9e48-70deaca2a5b1

Select all the combinations of propulsion system and applications that are typical among the following?

['Cold Gas propulsion for orbit insertion', 'Solid propulsion for orbit insertion', 'Liquid monopropellant for orbit insertion', 'Liquid monopropellant for attitude control', 'Electric propulsion for orbit maintenance and maneuvering', 'Liquid bipropellant for orbit insertion']

[0, 1, 0, 1, 1, 1]

ea7c422b-60f6-4178-9732-0d615939c26f

What is the typical range of specific impulse for liquid monopropellant systems?

['45 - 75s', '200 - 235s', '274 - 467s', '500 - 3000s']

[0, 1, 0, 0]

3f9f6c75-740b-4c5f-a010-231506efad98

Select all the advantages of monopropellant hydrazine propulsion systems over bipropellants propulsion systems?

['system simplicity', 'long term storability', 'capability to restart', 'higher specific impulse', 'lower toxicity']

[1, 1, 1, 0, 0]

Hydrazine monopropellant systems have lower Isp (max 230s) not higher than most bipropellants systems. Also hydrazine toxicity poses several challenges, and research is being conducted to find alternatives which are safer to handle.

beefd301-4e93-4e57-923b-3d992f6e8030

How does the combustion takes place for hydrazine monoprop system?

['Hydrazine ignites spontaneous in contact of an hydrogen isotope, typically deuterium', 'Hydrazine decomposes on a micro-fluidic chip, typically made of palladium enriched carbon nanotubes in a sillicon wafer', 'Hydrazine ignites spontaneous in presence of an high-voltage electric discharge, typically 20,000 - 30,000 Volts', 'Hydrazine decomposes on a catalyst material, typically iridium']

[0, 0, 0, 1]

2870f350-5488-40da-bd0c-e026b991b01f

What is the name of the nozzle cooling technique, sometimes using in expander cycles, where one of the propellant (usually the fuel but not always) passes around the nozzle to cool it?

['Regenerative cooling', 'Ablative cooling', 'Film cooling']

[1, 0, 0]

1a348c80-de10-43bc-ba82-d74ad7fd1f69

What does ablative cooling in rocket engine propulsion systems refer to?

['chamber walls made of ablative material which decomposes into gas when heat up, hence acting as a coolant', 'combustion-generated heat is conducted through the chamber walls and rejected through radiation', 'the heat is absorbed by a thin film coating made of ablatium']

[1, 0, 0]

ebd8e218-ba8f-482c-b7e1-6ee1eb7c92ec

What does AOCS usually refer to in Astronautics?

['Astronomical Observation and Calculation System', 'Advanced Orbital Communication Satellite', 'Aerodynamic Optimization for Crew Safety', 'Attitude and Orbit Control System']

[0, 0, 0, 1]

19af499b-7a42-4a72-b393-e63bb4fd6e5c

Which axis of the coordinate system for the ISS AOCS is used in the direction of the velocity vector?

['+X (roll)', '+X (pitch)', '+X (yaw)', '-X (roll)', '-X (pitch)', '-X (yaw)']

[0, 0, 0, 0, 0, 0]

The choice of the ISS fixed coordinate system is pretty much like in aviation where we have the forward portion of ISS oriented toward the velocity vector and that's a + X axis. X is also correspond to the roll.

07b3bd15-13d5-45ad-b0cc-9a64d5214561

In the LVLH coordinate system that is often used for AOCS, what is the direction of each axis ofr a spacecraft on orbit around the Earth?

['X towards the center of the Earth, Y towards the rear of the spacecraft, Z towards the north of the orbit', 'X towards the Noth of the orbit, Y towards the center of the Earth, Z towards the spacecraft velocity vector', 'X towards the spacecraft velocity vector, Y towards the south of the orbit, Z towards the center of the Earth']

[0, 0, 1]

70710915-a079-49fd-874a-28d9470489ea

ISS and Space Shuttle euler sequence was Pitch, Yaw, Roll. This is difference from most spacecraft. Which Euler sequence do spacecrafts in general?

['Yaw Roll Pitch (YRP)', 'Yaw Pitch Roll (YPR)', 'Roll Pitch Yaw (RPY)', 'Roll Yaw Pitch (RYP)']

[0, 1, 0, 0]

e904a2e2-67c6-4da6-820e-1861b040d617

How it is possible to maintain a certain orientation by spinning a spacecraft?

['Due to the electron spin', 'Due to the gyroscopic effect', 'Due to the rotational speed being waved']

[0, 1, 0]

c2bd96c1-08db-4bb3-bdc0-67097d6f174c

How is it possible to use gravity gradient for attitude control?

['For an elongated object, the gravity force at the bottom of the object is greater than the force at the top', 'For an elongated object, the gravity force at the top of the object is greater than the force at the bottom', 'For a spherical rotating object, the gravity at the bottom of the sphere is greater than the gravity at the top', 'For a spherical rotating object, the gravity gradient originates from the fluid forces momentum in the intern structure.']

[1, 0, 0, 0]

b185c125-a603-4e68-97bf-796ee0dd929a

Which of the following is the primary factor determine the voltage of a solar array?

['The temperature of the environment where the solar array is in', 'The solar cell thickness', 'The number of cells connected in series to form a string', 'The mounting structure of the solar cell']

[0, 0, 1, 0]

57f57993-5f84-46b7-82ab-37aba7f12d70

Which of the following time point is used to size a satellite photovoltaic system?

['Beginning-of-life power requirements', 'Average life power requirements plus a 10 to 20 margin', 'End-of-life power requirements']

[0, 0, 1]

This is because power requirement have to be met, even at end-of-life otherwise the satellite would not be able to operate nominally at towards the end of its mission. This results in the system often being oversized for BOL requirements and can cause power problems if not taken care of.

ca57a7ff-3145-4c26-ad77-1e8b1ce2fcb1

Which of the following are the lower costs cells that could be in use for satellite solar arrays?

['Thin film amorphous Silicon cells', 'Gallium-Arsenide Triple Junction cells', 'Indium Phosphide cells']

[1, 0, 0]

848d888b-d844-46ad-a5db-7b9fbaf9cb93

Which of the following rechargeable battery technologies used for satellite has the higher energy density?

['Li-ion', 'Ni-Cd', 'Ni-H2']

[1, 0, 0]

Ni-Cd has about 30 Wh/kg, Ni-H2 has about 60 Wh/kg and Li-ion more than 125 Wh/kg energy storage density

f84011f6-edb0-4748-ba0d-c5a01d1bee78

Assuming a similar lifetime, and temperature maintained range, which of the following orbit would enable to use secondary batteries with a higher depth of discharge?

['Low-Earth Equatorial Orbit mission', 'Sun-Synchronous Polar Orbit mission', 'Geostationary Orbit mission']

[0, 0, 1]

Geostationary satellite experience less frequent eclipse than Low-Earth orbiting missing, reducing the number of charge/discharge cycle on the batteries. Relaxing the number of charge/discharge requirement enables usually to increase the depth-of-discharge.

4efab579-4b0a-4647-9dff-4aaaf6f12713

Which of the following are typical ranges of load input power requirements in satellite engineering?

['Normal Steady State Voltage Range: 5 to 7 V DC', 'Normal Steady State Voltage Range: 25 to 21 V DC', 'Normal Steady State Voltage Range: 150 to 220 V DC', 'Max Current 60 Amp', 'Nominal Ripple 1 V peak to peak']

[0, 1, 0, 0, 1]

Typical max current is often around 15 Amp (even though not always!)

a95ff8d7-d775-4602-a2b9-52aa613af262

Which are the most common power bus control techniques used in satellite electrical power subsystems?

['Alternating Current Frequency Adjustment (ACFA)', 'Voltage Multiplication Regulation (VMR)', 'Capacitive Load Stabilization (CLS)', 'Direct Energy Transfer (DET)', 'Peak Power Tracker (PPT)']

[0, 0, 0, 1, 1]

7bff3a67-9181-48dd-811b-48ca49851e30

Which of the following buck-boost derived regulator is the most complex among the following?

['Full Bridge Regulator', 'Flyback', 'Two-switch Forward']

[1, 0, 0]

From least complex to most complex are the flyback, single switch forward, two switch forward, push-pull, and full-bridge regulators

ea3c5ee5-1439-4e00-9555-026fc3c8837f

Which technique used on spacecraft power regulators (buck-boost) enables to further enhance their efficiency?

['Resonant Mode Switching', 'Continuous Current Calibration', 'Voltage Ripple Reduction']

[1, 0, 0]

dda35b83-c23f-4682-b89c-b4d217366785

Which of the following power source in spacecraft design usually require storage in case of Eclipse?

['Fuell cells', 'Nuclear reactor', 'Radioistope Thermoelectric Generator', 'Solar Thermal Dynamic', 'Solar Photovoltaic']

[0, 0, 0, 1, 1]

Both solar thermal dynamic and solar photovoltaic do not generate power during eclipse so storage is require to keep the satellite powered on.

8d14f358-de2e-46fa-8eb2-26edb2eee900

Which of these statements are true of solid rockets?

['They are relatively simple to build and operate', 'They provide limited ability to control thrust', 'They inherently produce more thrust than liquid rockets', 'They generate a lot of noise and vibration']

[1, 1, 0, 1]

6a41ebbc-8a34-4036-a1b0-8507b0164ac1

Which of these statements are true of liquid rockets? Tell all that apply.

['They inherently produce less thrust than solid rockets', 'They must store the oxidizer and fuel propellant components onboard in separate compartments', 'To get high performance, they must use turbo pumps to direct the propellant into the combustion chamber', 'They encounter high temperatures and pressures during combustion']

[0, 1, 1, 1]

10f3799c-63b3-4154-af37-bb371b1fee35

When applying the idea rocket equation, which components usually comprise the the rocket initial mass ?

['Payload', 'Propellant', 'Structure']

[1, 1, 1]

The initial mass at launch consists of payload, propellant, and rocket structure. The final mass refers to when the propellant has been consumed, and thus consists of payload and structure.

195bc8ba-e67d-435d-b384-7d23ecc1e3c8

When applying the idea rocket equation, which components usually comprise the the rocket final mass ?

['Payload', 'Propellant', 'Structure']

[1, 0, 1]

The initial mass at launch consists of payload, propellant, and rocket structure. The final mass refers to when the propellant has been consumed, and thus consists of payload and structure.

85b1737f-ce24-40eb-9cac-71220489ded7

Consider a rocket in free space having two engines with identical Isp, connected to a single propellant system. Recall that the relationship between specific impulse and exhaust velocity is Vexhaust = go * Isp. If one engine fails, what is the impact on the total ΔV that can be obtained from the system?

['ΔV will double', 'ΔV will be cut in half', 'ΔV will stay the same']

[0, 0, 1]

If one engine fails, there is no change in specific impulse, or in the total amount of propellant available. Therefore, the total ΔV that is obtainable from the system is the same. However, the thrust is cut in half, so it will take twice as long to achieve the same ΔV (until the propellant is consumed).

9c2d1b44-c462-4db4-9664-7625b8b054c6

Consider a rocket carrying 100,000 kg of propellant, 10,000 kg of structure and 5,000 kg of payload. What is the structure fraction of this rocket?

['0.053', '0.075', '0.087', '0.019']

[0, 0, 1, 0]

The structure fraction is given by the ration of the mass of the structure (10,000 kg) divided by the sum of the structure, payload and propellant (100,000 + 10,000 + 5,000). The result is 10,000 / 115,000 which is approximately 0.087.

655147dd-fc22-4c82-a964-a234ef65c2b7

Consider a rocket carrying 100,000 kg of propellant, 10,000 kg of structure and 5,000 kg of payload. Using the ideal rocket equation, and assuming a specific impulse of 450s, what would be value of the Delta V in m/s that this rocket would be able to produce if all the propellant is consumed in one stage?

['8991 m/s', '9991 m/s', '10991 m/s', '11991 m/s', '12991 m/s']

[1, 0, 0, 0, 0]

The ideal rocket equation gives ΔV = g0 * Isp * ln(mass_initial / mass_final). g0 = 9.81 m/s^2 Isp = 450 s We need to compute the initial mass of the rocket and the final mass of the rocket. 1. Initial mass of the rocket: initial_mass = payload_mass + structure_mass + propellant_mass = 5,000 + 10,000 + 100,000 = 115,000 kg. 2. Final mass of the rocket (everything except the propellant that has been burnt) final_mass = payload_mass + structure_mass = 5,000 + 10,000 = 15,000 kg ΔV = 9.81 * 450 * ln( 115,000 / 15,000) = 8991 m/s

830a0d7a-0ce6-4c92-9a65-e7599ac1b700

What would be the Delta V in m/s of the first stage of a rocket under the following conditions?

['1519', '2519', '3519', '4519', '5519']

[0, 1, 0, 0, 0]

The ideal rocket equation gives ΔV = g0 * Isp * ln(mass_initial / mass_final). g0 = 9.81 m/s^2 Isp = 450 s We need to compute the initial mass of the rocket and the final mass of the rocket. 1. Initial mass of the rocket before the first stage has brunt (all the propellant is remaining) initial_mass = payload_mass + structure_mass + propellant_mass = 5,000 + 10,000 + 100,000 = 115,000 kg. 2. Final mass of the rocket after first stage burnt (everything is included except the half of the propellant that has been burnt) final_mass = payload_mass + structure_mass = 5,000 + 10,000 + 100,000/2 = 65,000 kg ΔV = g0 * Isp * ln(115,000 / 65,000) = 2519 m/s

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What Delta V can be achieve by the second stage of a rocket, after first stage has been jettisoned and under the following assumptions?

['6910 m/s', '7910 m/s', '8910 m/s', '9910 m/s']

[0, 1, 0, 0]

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What does ECLSS refer to in astronautics?

['Engineering Calibration and Logistics Support Services', 'Extra-terrestrial Colonization and Landing Systems', 'Electrical Circuitry and Load Support Systems', 'Environmental Control and Life Support System']

[0, 0, 0, 1]

e9c6d3d7-c413-49b8-9877-4f95294d4b70

Which of the following environmental control requirements are in general specific to human spaceflight, hence not applicable to unmanned satellite missions?

['Atmospheric Pressure Control', 'Temperature Control', 'Waste Disposal', 'Water and Food']

[1, 0, 1, 1]

326efd57-822c-45e9-a16e-707e7389f102

Which of the following is true about ECLSS Closed Loop System in comparison to Open-Loop ECLSS?

['They are reliable because there are a few moving parts', 'Resource scale linearly with flight duration', 'They require less resupply', 'They are more complex and more expensive', 'Recycling equipment can increase the launch mass']

[0, 0, 1, 1, 1]

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What is the primary driver to choose between a closed-loop or an open-loop ECLSS?

['Spacecraft Size', 'Crew Size', 'Mission Duration', 'Launcher reliability']

[0, 0, 1, 0]

Due to the additional mass from recycling equipement, open-loop ECLSS are more interesting for short-term missions. There is a crossover point in the mission duration after which the initial investment of bringing with you recycling equipment becomes more interesting (in terms of total mass) due to the recycled matter.

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Which of the following recycling is represent the more mass savings using a closed loop ECLSS?

['Food production from wastes', 'Oxygen recovery from CO2', 'Water recycling', 'Leaks prevention']

[0, 0, 1, 0]

Recycling water is by far the most important source of mass saving

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Which of the following are the most import source of water consumption on-board ISS missions?

['Drinking water', 'Food preparation water', 'Clothes wash water']

[1, 0, 0]

Clothes are not washed onboard the ISS otherwise it would consume too much water. Food preparation water is usually half of drinking water requirements.

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Assuming there are 3 sources of independent errors on the knowledge of the volume of a given reservoir. These independent errors are 0.1 L, 0.2 L and 0.5 L. Which is the combined errors of these 3 sources of errors?

['0.30 L', '0.50 L', '0.55 L', '0.80 L']

[0, 0, 1, 0]

If the errors are independent the combined error is given by the square root of the sum of individual error squared. sqrt(0.1ˆ2 + 0.2ˆ2 + 0.5ˆ2) = 0.547. L

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What is the formula used to combined errors (e1, e2, e3) which are depend from each other? Assume that all errors are given in absolute values.

['error = e1 + e2 + e3', 'error = e1ˆ2 + e2ˆ2 + e3ˆ2', 'error = max(e1, e2, e3)', 'error = sqrt(e1 + e2 + e3)', 'error = sqrt(e1ˆ2 + e2ˆ2 + e3ˆ2)']

[1, 0, 0, 0, 0]

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How do you usually compute a risk score in aerospace risk management?

['Division of severity by probability of occurrence', 'Summation of individual risk severity', 'Average probability of occurrence of all risks', 'Multiplication of probability of occurrence by risk']

[0, 0, 0, 1]

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What is usually true when talking about spacecraft active redundancy systems?

['Often used in non-critical application', 'Often used in critical application', 'Suitable for digital systems but not for mechanical systems', 'Requires manual switching to backup components upon failure', 'No action is needed to ensure the service continuity after the failure']

[0, 1, 0, 0, 1]

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What are trade trees in astronautics?

['A catalog of spacecraft components traded on international markets', 'A new class algorithms for optimizing fuel consumption during space missions', 'Mathematical models for predicting the trajectory of celestial bodies', 'A hierarchical decomposition of decisions to make the most important decisions first']

[0, 0, 0, 1]

5b7a8008-b65d-44c0-99c8-7acb5ac6a59d

Which of the following best describe push broom scanning technique for electro-optical instruments?

['Scanning a single detector element on the ground in the cross-track direction', 'Scanning covering a full swath width using a linear arrangement of detector elements', 'Scanning using a 2-dimensional array of detector element']

[0, 1, 0]

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True of false: Active RF systems can be used in satellite observation payload to observe emission of the highest energy photons from astrophysical objects (including Sun and supernovae)?

['True', 'False']

[0, 1]

False because, the capability to observe emission of the highest energy photons from astrophysical objects (including Sun and supernovae) is usually provided by gamma ray payloads while active RF system like radars and synthetic aperture radars (SARs) are used for RF imagery of precipitation in clouds, surface wakes on the ocean and detailed topography of Earth and other planetary solid surfaces.

81c196de-f705-44da-875d-10df8dc84c1b

Which of the following was the first known SAR in space?

['CALIPSO', 'ICESAT', 'SEASAT', 'TRMM']

[0, 0, 1, 0]

SEASAT launched in 1978 is the first known SAR in space and operated in L-band .

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Which of the following aberrations can be fully corrected by Doublet/Schmidt optical systems?

['Lateral Chromatic', 'Length Chromatic', 'Astigmatism', 'Curvature of Field', 'Spherical']

[1, 1, 0, 0, 1]

1e3d4af8-4eaf-4730-8155-fb1a9cab4ecf

Which of the following reflective optical system is analogous to the Tele-optic refractive optical system?

['Lens Doublet', 'Schmidt', 'Cassegrain', 'TMA (Three-mirror anastigmatic)']

[0, 0, 1, 0]

c68460d2-8cd8-4f88-a407-6cc47d3af00d

Which of the following best describe a spherical aberration?

["when a sharp image is formed on a focal surface which isn't flat", 'when light from the periphery of a spherical lens or mirror is focused nearer the element than light from the center', 'when an otherwise sharp image is distorted in shape, such as when straight light on the surface being viewed appear curved on the focal plane', 'dispersion of the light due to the refractive index of a lens being a function of the wavelength']

[0, 1, 0, 0]

881245b2-6dfa-4b39-93fa-454b10919ef7

Assuming you are calculating parameters for a passive optical sensor, what would be the sensor dynamic range DR (with respect to cold space) assuming that the number of photocarriers available Ne = 7.3e6 (evaluated for an ideal detector) and number of read-out noise electrons is Nr = 5000?

['DR = Neˆ2 / Nr = 1.07e10', 'DR = Ne / Nr = 1460', 'DR = sqrt(Ne) / Nr = 0.54']

[0, 1, 0]

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Which type of satellite sensor should you select for you AOCS if you need an accuracy of 0.1 deg and have string mass constraint?

['Sun Sensor', 'Star Sensor', 'Magnetometer']

[1, 0, 0]

Sun sensors have a typical accuracy of 0.005 def to 3 deg with mass varying from 0.1 to 2 kg which is accurate but weight less than star sensors. Magnetometers are not accurate enough for this performance requirements

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Which of the following definition is correct in the domain of spacecraft mechanisms?

['Deployables - devices used to provide optical adjustments for space instruments', 'Drives - devices requiring continuous or frequent operation for the life of the mission where wear, lubrication and life are critical', 'Instrument mechanisms - devices generally used to create spacecraft on-orbit configurations which are larger than can be packed in the launch vehicle fairing']

[0, 1, 0]

34f1d6d5-a95f-4e56-b19c-8a54a8cb5da3

What is true about MLI for satellites?

['MLI stands for Micro Layer Insulation', 'MLI stands for Multiple Layer Insulation', 'Composed of multiples layers of low-emittance films with low conductivity', 'Composed of micrometer thickness layers of high-emittance films sandwiched with carbon fiber reinforced mesh']

[0, 1, 1, 0]

8c856182-3296-4088-b56f-9be8c16eb27e

Which of the following thermal dissipation mechanism is usually not accounted for for satellite thermal balance?

['Conduction', 'Radiation', 'Convection']

[0, 0, 1]

a63a44bc-930e-4048-986e-2a2f80bf4a53

Which of the following thermal control component is used to warmup the catalyst bed of hydrazine thrusters?

['Surface finish', 'Louvers', 'Patch heater', 'Cartridge heater', 'Grooved Heat pipe']

[0, 0, 0, 1, 0]

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Which of the following reviews according to European Space Agency space program life cycle comes last?

['CDR', 'MCR', 'PDR', 'SRR']

[1, 0, 0, 0]

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Select all which are commonly accepted end item verification methods?

['Verification by inspection', 'Verification by analysis', 'Verification by test', 'Verification by similarity']

[1, 1, 1, 1]

All 4 methods are widely recognized methods of formal verification. Some users add another category of verification method: demonstration.

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What are burn-in tests for spacecraft components?

['application of radiation stesses simulating single events', 'application of electrical stresses above normal use, or rating, usually high voltage', 'application of pseudo-random vibration spectum predicted for launch and atmospheric ascent', 'sustained high temperature operation over pre-defined time span', 'application of transients simulating those resulting from sudden release of loads (staging/separation, deployment)']

[0, 0, 0, 1, 0]

828838d1-992e-412b-91ea-fe10ed216ec5

What type of environmental tests for units under tests correspond to rapid temperature transitions between defined extremes under normal atmospheric conditions, dwelling at extremes for hours at a time?

['Pyro-shock', 'Thermal vacuum', 'Burn-in', 'Thermal cycling', 'Enhanced low dose rate sensitivity (ELDRS)']

[0, 0, 0, 1, 0]

2147b0f6-662f-4872-8b8e-18e280d5e29d

How can you compute the MTBF assuming you know the failure rate lambda?

['lambdaˆ2', 'lambdaˆ(1/2)', '1 / lambda', 'lambda / (1 - lambda)']

[0, 0, 1, 0]

beb8a417-4d86-44f1-b07b-e3ba7dbf6194

Consider a propellant feed system with two valves in series. Valve one has a probability of failure in close position of 0.01 and the other valve has a probability of failure in close position of 0.02. If any of the valve fail in the close position, the propellant cannot flow anymore. What is the overall reliability R of the feed system to still be open?

['Approximately 0.95', 'Approximately 0.97', 'Approximately 0.03', 'Approximately 0.02', 'Exactly 0.87', 'Exactly 0.76']

[0, 1, 0, 0, 0, 0]

R = (1 - 0.01)*(1-0.02) = 0.99 * 0.98 = approx. 0.97

0908d052-016a-410e-a96c-ab10b813b4f6

Which of the following languages will you have to learn as a minimum if your are selected as an Astronaut?

['French', 'Chinese', 'English', 'Japanese', 'Russian']

[0, 0, 1, 0, 1]

1f9fc6c5-c327-4450-80bf-270c646f093d

Which of this center are knwon for Astronaut training?

['Jet Propulsion Laboratory', 'Kennedy Space Center', 'Johnson Space Center', 'Star City', 'ESA/ESTEC', 'ESA/EAC']

[0, 0, 1, 1, 0, 1]

fba43aad-6a08-4d7a-946e-d73a65a99742

Which of the following system enable astronaut to experience up to 20 seconds of weightlessness?

['zero-G flight', 'Drop tower', 'Centrifuges', 'Water Buoyancy Lab']

[1, 0, 0, 0]

cf12aa3a-38cc-4067-b829-0510a550874e

What should you do first when a non-confirmance is detected according to the ECSS?

['Implement corrective and preventive actions', 'Call the supplier and fire them', 'Issue a non-conformance test plan (NCTP)', 'Organize an internal non-conformance review board (NRB)', 'Issue an internal Non-conformance report (NCR)', 'Notify the customer and call out for a customer non-conformance review board (NRB)']

[0, 0, 0, 0, 1, 0]

793b77a7-204e-4acc-a252-b56ed5e25263

Which of the following are commonly accepted dispositions of minor non-conformances?

['Return to supplier', 'Use "As Is"', 'Rework', 'Repair', 'Scrap', 'Test again until test pass']

[1, 1, 1, 1, 1, 0]

7e74f9c0-2899-40b3-a143-19cd380ebdd2

What type of orbit is famous for its long dwell time over North America and Russia while passeing quickly over the southern hemisphere?

['Geostationary Orbit', 'Polar Orbit', 'Sun Synchronous Orbit', 'Korolev Orbit', 'Molniya Orbit', 'Kennedy Orbit']

[0, 0, 0, 0, 1, 0]

6e49ffae-e12f-4053-b482-0f35294b805c

Which of the following gas is the main component of the Mars atmosphere?

['N2', 'O2', 'CO2', 'CH4', 'Ar']

[0, 0, 1, 0, 0]

Mars Atmosphere is made up to 96% of CO2

80f3bfa3-5198-4c0f-a137-4c679b192a58

How long do Lunar night last near the Moon equator (period of time where your solar array will not generate electricity and where you would have to run on batteries)

['3.5 hours', '35 hours', '350 hours', '3500 hours']

[0, 0, 1, 0]

73f86516-6e00-4668-91e8-9e15ebb3912e

Which can you find on the Moon surface?

['Liquid methane', 'Lava tubes', 'Ilmenite', 'Iron, Titanium, and Aluminum oxides', 'A thin atmosphere']

[0, 1, 1, 1, 0]

10a3f4eb-6269-41c8-9a78-410ff0189ffb

Which mission types to Mars often include a Venus fly-by?

['Conjunction mission', 'Cross-trapped mission', 'Opposition mission', 'S-type mission', 'J-type mission']

[0, 0, 1, 0, 0]

ed958ac6-616f-479d-b73c-203016fdf5d5

Which of the following methods are well known for propellant gauging in satellite propellant subsystems?

['Pressure-Volume-Temperature', 'Entropy-Enthalpy-Gibbs', 'Book-keeping', 'Station-keeping']

[1, 0, 1, 0]

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