ANALYSIS OF ELECTRIC PROPULSION PROPELLANT TYPE FOR CREWED MARS MISSIONS

An analysis of alternative Hall thruster propellants to xenon for a crewed Mars mission using nuclear electric/chemical propulsion is performed. Xenon, the preferred propellant when considering storage density and Hall thruster performance, is not readily available in the quantities needed for this mission, creating significant mission planning challenges. Therefore, this analysis considers the use of more available propellants and multiple storage strategies. This includes gaseous and cryogenic storage of krypton and argon and solid storage of zinc. The 1.8 MW Compass vehicle design and mission planning for a 2039 opposition class mission to Mars is utilized as a reference. A framework is developed to re-design the reference vehicle and recalculate the mission for each propellant type. The results indicate that cryogenic krypton or argon, and zinc may be feasible replacements to xenon for this mission. This result is largely driven by the comparable storage density/tank weight of these propellants to standard xenon. The low storage density of gaseous krypton and argon, coupled with launch vehicle mass/volume requirements, leads to the inability to meet mission requirements. The key limitations of this analysis and outstanding development challenges are discussed in the context of the EP system and each alternative propellant. The framework developed in this work is extendable to analyze any Hall thruster propellant for crewed Mars missions.