Solar Sails for Mars Cargo Missions

Abstract

This paper presents an analysis of Solar Sails for the Mars Cargo Mission. The figures-of-merit used are the total system Initial Mass in Low Earth Orbit (IMLEO) and Trip Time. The total IMLEO includes the payload, solar sail, and any orbit transfer vehicle (OTV) required to move the sail and its payload to the operational altitude of the sail (e.g., 2.000 km minimum altitude Earth orbit for the solar sail due to air drag). Once the sail and its payload are transported to the sail’s minimum operational orbit by the OTV, the sail begins its Earth-escape spiral and heliocentric transfer to the orbit of Mars. In order to minimize the payload’s Earth-to-Mars trip time, the sail does not perform a Mars orbit insertion capture spiral but rather deploys its payload during Mars flyby. The payload then aerobrakes into Mars orbit or to the surface to await arrival of the crewed portion of the mission. The sail loiters in heliocentric space until it is time to return to Earth. Note that one important constraint on the payload’s Earth-to-Mars trip time is the requirement that the payload be delivered to Mars (and be checked-out and verified operational) before the crew departs Earth at the next Earth-Mars launch opportunity. We further assumed that the solar sail would be a reusable system; thus, in addition to delivering the payload to Mars prior to the next crew departure, the solar sail must return to Earth before the next sail Earth-departure opportunity. With these constraints, the solar sail areas required for a 58 and 72 metric ton (MT) payload are, respectively, 20 and 25 km2. The corresponding IMLEO values are 149 and 185 MT, such that the total transportation system (sail and OTV) is only 1.6 times the payload mass.