Commerce/T ransport The cargo ship burns into HEEO, and matches with the aerobrake left there by the colony ship. This aerobrake was sized specifically for the cargo ship. After aerobraking, the cargo ship ends up in LEO, ready to be unloaded. Each cargo ship carries 180 tons of water. Also, the ship itself represents almost 65 tons of useful mass. The 10 ships the first mission is equipped to build represent almost 2500 tons of returned material, which means a MPBR (Mass Pay Back Ratio) of about 8. By the time the first cargo ship arrives in LEO, the crew module/space platform for the second mission will be in orbit. Here, enough water will be electrolysized to fuel an OTV that will put the aerobrake back in HEEO. The rest of the water will be stored. Combined with water from the second cargo ship (minus enough once again to put the aerobrake in HEEO), there is now enough to launch the second group of colonists. This vehicle will burn directly from LEO to MTO, and will consist of just a crew module/storage module/Mars aerobrake combination. Depending on the colony's needs at the time, payload may be sacrificed in order to carry more people. (Note: The LEO-HEEO aerobrake would be designed to have a lifetime of 50 to 100 uses, before replacement is required. Repairs and refurbishment could occur after
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