Combining Solar Electric Propulsion and chemical propulsion for crewed missions to Mars
This paper documents the results of an investigation of human Mars mission architectures that leverage near-term technology investments and infrastructures resulting from the planned Asteroid Redirect Robotic Mission (ARRM), including high-power Solar Electric Propulsion (SEP) and a human presence in Lunar Distant Retrograde Orbit (LDRO). The architectures investigated use a combination of SEP and chemical propulsion elements. Through this combination of propulsion technologies, these architectures take advantage of the high efficiency SEP propulsion system to deliver cargo, while maintaining the faster trip times afforded by chemical propulsion for crew transport. Evolved configurations of the Asteroid Redirect Vehicle (ARV) are considered for cargo delivery. Sensitivities to SEP system design parameters, including power level and propellant quantity, are presented. For the crew delivery, liquid oxygen and methane stages were designed using engines common to future human Mars landers. Impacts of various Earth departure orbits, Mars loiter orbits, and Earth return strategies are presented. The use of the Space Launch System for delivery of the various architecture elements was also investigated and launch vehicle manifesting, launch scheduling and mission timelines are also discussed. The study results show that viable Mars architecture can be constructed using LDRO and SEP in order to take advantage of investments made in the ARRM mission.
Human and Robotic Exploration Missions to Phobos Prior to Crewed Mars Surface Missions
Phobos is a scientifically significant destination and exploring it would facilitate the development and operation of the human Mars transportation infrastructure, unmanned cargo delivery systems and other Mars surface systems. In addition to fostering development of systems relevant to Mars surface missions, exploring Phobos offers engineering and operational opportunities that could enhance subsequent Mars surface operations. These opportunities include the use of low-latency teleoperations to control Mars surface assets associated with exploration science, human landing-site selection, and infrastructure development, which may include in situ resource utilization to provide liquid oxygen for the Mars ascent vehicle (MAV). A human mission to the moons of Mars would be preceded by a cargo predeploy of a surface habitat and a pressurized excursion vehicle (PEV) to Mars orbit. Once in Mars orbit, the habitat and PEV would spiral to Phobos using solar electric propulsion-based systems. When a crewed mission is launched to Phobos, it would include the remaining systems to support the crew during the Earth-to-Mars transit and to reach Phobos after insertion into Mars orbit. The crew would taxi from Mars orbit to Phobos in a spacecraft that is based on a MAV to join with the predeployed systems. A mostly static Phobos surface habitat was chosen as a baseline architecture. The habitat would have limited capability to relocate on the surface to shorten excursion distances required by the PEV during exploration and to provide rescue capability should the PEV become disabled. To supplement exploration capabilities of the PEV, the surface habitat may use deployable EVA support structures that allow astronauts to work from portable foot restraints or body restraint tethers in the vicinity of the habitat. Prototype structures were tested as part of NASA Extreme Environment Mission Operations (NEEMO) 20. PEVs would contain closed-loop guidance and provide life support and consumables for 2 crewmembers for 2 weeks plus reserves. The PEV has a cabin that uses the exploration atmosphere of 8.2psi with 34% oxygen. This atmosphere enables EVA to occur with minimal oxygen prebreathe before crewmembers enter their EVA suits through suit ports, and dust control to occur by keeping the suits outside the pressurized volume. When equipped with outriggers, the PEV enables EVA tasks without the need to anchor. Tasks with higher force requirements can be performed with PEV propulsion providing the necessary thrust to counteract forces. Exploration of Phobos builds heavily on the development of the cis-lunar proving ground and significantly reduces Mars surface risk by facilitating the development and testing of habitats, MAVs, and pressurized rover cabins that are all Mars surface forward.
Fortune and Responsibility in Calderón's La gran Cenobia
La gran Cenobia deals with the war between Queen Zenobia of Palmyra and the Emperor Aurelian. Calderón de la Barca draws most of his information from historical sources; the dramatist, however, changes history and adapts it to his own dramatic purpose. The theme of Fortune gives unity to the play. Aureliano is portrayed as a tyrant who, to prove his independence from Fortune, behaves tyrannically, causing his eventual downfall. Cenobia believes that Fortune controls her life, but does not acknowledge that her own actions contribute to her misfortune. The analysis concludes that Fortune, as depicted in this play, is not an omnipotent and blind force, but what one has forged with his or her own actions coupled with the actions of others and circumstance.