Mars Sample Return Orbiter concepts using Solar Electric Propulsion for the post-Mars2020 decade

Since the selection of the proposed Mars 2020 mission as a Rover with the capability of sample collection and caching, there has been renewed interest in subsequent mission concepts to return Mars samples to Earth. The general architecture for this series of missions is outlined in the Planetary Science Decadal Survey of 2011. The role of the Sample Return Orbiter (SRO) in The 2011 Decadal Survey MSR architecture was to collect an orbiting sample (OS) from low Mars orbit and deliver it to Earth's surface. The architecture focused on chemical propulsion orbiters with ballistic and aerobraking trajectories that were dedicated entirely to the capture of orbiting samples and returning them to the surface of the Earth. Recent concepts have explored the use of Solar Electric Propulsion (SEP) to Mars and for the return to Earth. SEP could enable significant mission flexibility which includes: lower launch mass or increased mass delivery capability to Mars orbit and return to Earth; longer launch periods for both launch and Earth return; consistency of design across launch opportunities; access to both high and low Mars orbit altitudes; increased on-orbit ΔV budgets for orbit changes and sample rendezvous; and greater control over Earth arrival speed and geometry. With this flexibility come opportunities to: save launch cost; add functions such as remote sensing observations, secondary payload deployment, and relay telecommunications; and choose between direct return of Mars samples to the Earth's biosphere or capturing them to a stable long-term orbit around the Earth. This paper compares the previous SRO chemical-ballistic concepts with the recent SEP orbiter concepts. We will show the potential benefits gained by the inherent flexibility of SEP as applied to launch mass, launch periods, Earth return opportunities, on-orbit ΔV and other architectural drivers.