The third Mars mission is a one-way cargo flight which departs Earth in November 2009 for Phobos. The cargo is an automated propellant production plant designed to operate on Phobos and a ‘dry' MCL loaded with 45 tons of equipment to upgrade the Mars outpost to human-tended base status. The flight arrives in August 2010, the vehicles aerobrake separately in the Martian atmosphere and rendezvous separately with Phobos. The propellant plant begins telerobotic operation to produce water and then propellants from the carbonaceous chondrite material of Phobos, so that the Mars gateway station will take on operational status the following year. The MCL ‘docks' with Phobos and awaits the arrival of the next manned mission. The fourth mission departs Earth in November 2011 using the same refurbished MPV and arrives at Mars in September 2012. The MPV aerobrakes at Mars and proceeds to Phobos where the crew controls fueling of the MCSV, the MCL, and the MPV. After propellant transfer the MCL descends to the vicinity of the Mars Outpost and is followed shortly by the MSCSV containing the entire crew. During the year long stay on the surface the outpost is upgraded to base status with the capability to grow some food and utilize in situ resources to increase stored supplies of air and water. In August 2013, the crew secures the Mars base and returns to the Phobos gateway in the MCSV. They return to Earth in the gateway refueled MPV, which is then used in subsequent cycles. 3 Description of Potential Nuclear Elements Since this paper addresses the benefits of space nuclear power we will only describe, in depth, those transportation and surface elements for which acceptable nuclear alternatives exist. At this moment, the acceptable nuclear alternatives are all orbit-to-orbit transfer vehicles. Other nuclear alternatives have been proposed (e.g. for surface landers), but they present serious environmental concerns and are beyond the scope of this paper. Lunar Transfer Vehicles The lunar transfer vehicle is capable of delivery of cargo or crew modules to Low Lunar Orbit (LLO), and return of cargo or crew to LEO. The baseline propulsion system is LO2/LH2, with other options including nuclear thermal rockets, and nuclear electric propulsion. For the purposes of this study, it was assumed the baseline LEO- to-LLO transportation vehicle would be the LO2/LH2 Space Transportation Vehicle (STV), which is the subject of current Phase A studies. Support of the lunar evolutionary mission cases is a primary STV design requirement. We will assume the manned missions will always use chemical propulsion, and concentrate on the lunar cargo missions as possible applications for space nuclear power. For cargo missions, the Lunar Cargo Vehicle assembled in LEO includes the transfer stage with droptanks, and the fully fueled lunar cargo lander with payload. Upon arrival at lunar orbit, the cargo lander detaches and performs its lunar descent and cargo delivery. The lunar transfer stage departs lunar orbit and splits into tankset and propulsion module prior to Earth aeromaneuver. The tankset is expended and the propulsion module performs an aeromaneuver and returns to LEO for reuse. A sequential performance summary is shown for the chemical lunar cargo mission in Table I. The nuclear thermal rocket propulsion system could also be a partially reusable system, with the propulsion elements and avionics packaged in an aerobraked module and the hydrogen propellant tankage discarded after propellant depletion. Trip time for the NTR system is comparable to the chemical system, as both systems require similar delta-V's for lunar transfer. A sequential performance summary for the NTR
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