In many other studies of Mars missions, LOx/hydrogen is usually not chosen, due to the long term storage problems associated with hydrogen. However, included in the cargo on this mission are several refrigeration units [17, 22, 23] (to be used to liquify propellants on Deimos). One or more of these units would be used enroute to limit hydrogen boil-off. The crew section would be very similar to the crew module planned for the NASA space station. A crew of six is assumed, and the module is assumed to mass 30 metric tons. (The NASA crew module on Space Station will weigh about 20 tons. The extra weight comes from extra life support supplies and equipment and the storm cellar: a chamber within the crew module where the crew would go in the event of a solar flare [7]). The storage/power module, which contains life-support system supplies, food, solar power system, and equipment, will mass about 27 tons (Table I). The life support system does not have to be as high-tech as is usually envisioned for manned Mars missions, because the colonists will have access to the resources of Deimos upon arrival. Thus, the water recovery system needs to function for only eight or nine months, rather than the three or four years mentioned in most mission studies. The ship is shown in Fig. 5. Construction The existence of a commercially available 10-ton-to-LEO ELV is assumed (late 1990s-early 2000s time-frame). The Mars ship is constructed in a 300 km circular orbit. The crew module would be launched first, for two reasons: 1. It could serve as a ‘construction shack', housing astronauts while the rest of the ship
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