A MIT group has found that taking a detour to the moon to refuel would reduce the mass of a Mars mission upon launch by 68 percent.
The most mass-efficient path involves launching a crew from Earth with just enough fuel to get into orbit around the Earth. A fuel-producing plant on the surface of the moon would then launch tankers of fuel into space, where they would enter gravitational orbit. The tankers would eventually be picked up by the Mars-bound crew, which would then head to a nearby fueling station to gas up before ultimately heading to Mars.
Missions to Mars and other distant destinations may benefit from a supply strategy that hinges on “in-situ resource utilization” — the idea that resources such as fuel, and provisions such as water and oxygen, may be produced and collected along the route of space exploration. Materials produced in space would replace those that would otherwise be transported from Earth.
For example, water ice — which could potentially be mined and processed into rocket fuel —has been found on both Mars and the moon.
The model assumes a future scenario in which fuel can be processed on, and transported from, the moon to rendezvous points in space. Likewise, the model assumes that fuel depots can be located at certain gravitationally bound locations in space, called Lagrange points. Given a mission objective, such as a set of weight restrictions, the model identifies the best route in the supply network, while also satisfying the constraints of basic physics.
Simple logistics strategies such as “carry-along” and Earth-based “resupply” were sufficient for past human space programs. Next-generation space logistics paradigms are expected to be more complex, involving multiple exploration destinations and insitu resource utilization (ISRU). Optional ISRU brings additional complexity to the interplanetary supply chain network design problem. This paper presents an interdependent network flow modeling method for determining optimal logistics strategies for space exploration and its application to the human exploration of Mars. It is found that a strategy utilizing lunar resources in the cislunar network may improve overall launch mass to low Earth orbit for recurring missions to Mars compared to NASA’s Mars Design Reference Architecture 5.0, even when including the mass of the ISRU infrastructures that need to be pre-deployed. Other findings suggest that chemical propulsion using LOX/LH2, lunar ISRU water production, and the use of aerocapture significantly contribute to reducing launch mass from Earth. A sensitivity analysis of ISRU reveals that under the given assumptions, local lunar resources become attractive at productivity levels above 1.8 kg/year/kg in the context of future human exploration of Mars.
SOURCES- MIT, Technology Review, Journal of Spacecraft and Rockets.