An architecture for sustainable human exploration of Mars enabled by water from the lunar poles

This paper describes an architecture for human exploration of Mars that would be enabled by 10 metric tons (t) per day of ISRU water extracted at the lunar poles. The architecture involves a concept for a standardized “self-propelled tank” having an 85% propellant mass fraction that could hold up to 51 t of LH
₂
/LO
₂
propellant. A variant of this tank would be equipped with landing legs so that, when fully-loaded, it could lift another full tank into Low Lunar Orbit (LLO), release it, and have enough propellant remaining to mate with an empty tank and to land safely back at the ISRU plant in a lunar polar crater. Two such pairs would be launched each lunar sidereal month such that the two payload tanks could mate together in LLO and depart to a carefully-selected High Earth Orbit (HEO). This orbit is such that exactly one tank would be consumed propelling one full tank to HEO and returning one empty tank from HEO to LLO, with both tanks arriving empty. Also, a Low Earth Orbit (LEO) is selected where two full tanks in HEO could mate together such that one full tank arrives in LEO while the other tank has just enough propellant left to return to HEO, arriving empty. This combination of capabilities allows payloads to be launched from Earth into LEO, where they could be ferried to HEO using lunar propellant. Such payloads could be assembled together as stacks in HEO, where an array of full tanks accumulated over time from lunar ISRU could propel them on Hohmann transfers to Mars on every opportunity (every 26 months). The notional payload we envision launching to Mars every 26 months includes two 31 t Deep Space Habitats (DSHs, one for the outbound journey and one for the return journey) plus a 48 t Mars Surface Habitat with Ascent Vehicle (MSHAV). The stack departs HEO with a small burn from the array of 24 standardized propellant tanks - just enough to put it on an Oberth Maneuver trajectory, swinging by the top of the Earth's atmosphere where the main Trans-Mars Injection (TMI) burn occurs, consuming 7.8 of the 24 tanks. No tanks are jettisoned, so as to make this architecture sustainable and affordable. Upon arrival at Mars ~7-9 months later, another 9.2 tanks are burned to inject the stack into Low Mars Orbit (LMO). Exactly one tank is burned to de-orbit the MSHAV, reducing its velocity to zero at some point deep in the Mars atmosphere. The one tank that de-orbits the Mars entry stack is lost. After ~500 days on the Mars surface, the MAV launches and mates with the main stack in LMO. The returning DSH and the 23 tanks depart LMO with a burn of 4.3 tanks for Trans-Earth Injection. Upon arrival at Earth, 1.7 tanks are burned to inject into HEO, where the tanks could be shuttled back to the lunar surface for re-fueling. The DSH is mated with a single full tank at HEO that brings it to LEO to rendezvous with a crew capsule for re-entry.