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

Abstract

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 orbitaltitudes; increased on-orbit ∆V 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 ∆V and other architectural drivers.

NASA must protect Earth's biosphere even if Mars samples hold mirror life – motivating planetary protection with new scenarios like mirror life - survey of recent research relevant to a Mars sample return - and how to keep Earth's biosphere 100% safe with a miniature telerobotic lab above GEO, and protect other biospheres 100% with sterile robotic explorers

“…One way is to return the sample via a lunar retrograde orbit (actually a prograde orbit around Earth but retrograde around the Moon). Lock et al proposed returning a sample from Mars using a close flyby of Earth followed by a flyby of the Moon which then can get captured in a lunar retrograde orbit with a delta v of only 100 meters per second (Lock et al, 2014). First they need to reduce the speed of the spacecraft relative to Earth on the flight back, to make this capture easier.…”

“…This increases the fuel mass by about 30% for their hypothetical mission. Assuming a 1000 kg dry mass and fuel mass of just under 370 kg for the direct flight with aerocapture, this increases to a fuel mass of just under 480 kg for the low energy transfer (Lock et al, 2014).…”

NASA and ESA are likely to be legally required to sterilize Mars samples to protect the environment until proven safe – the technology doesn't yet exist to comply with the ESF study's requirement to contain viable starved ultramicrobacteria proven to pass through 0.1 micron nanopores - proposal to study samples of astrobiological interest remotely in a safe high orbit above GEO with miniature life detection instruments – and immediately return sterilized subsamples to Earth

“…One way for the ERV to get captured to above GEO, starting from a return orbit from Mars is via a distant retrograde orbit (DRO) around the Moon as an intermediary orbit (Lock et al, 2014). A DRO is essentially an Earth centered prograde orbit with the same orbital period as the Moon with the satellite alternating between outside of the Moon and inside of the Moon in its orbit, in such a way as to also be a Moon centered retrograde orbit.…”

NASA and ESA will need to sterilize Mars samples to protect Earth's biosphere, because of the many years to complete the legal process and then build a receiving facility to the legally approved design - recommendation to study unsterilized samples telerobotically in a safe orbit above GEO, and return sterilized sub-samples to Earth immediately - PLEASE READ LATEST VERSION AT: https://osf.io/rk2gd

“…This is also perfect for a continuous thrust. It would start by spiralling outwards to a high orbit several million kilometers from Mars, and from there, if the right moment is chosen to depart from that distance orbit around Mars, the delta v to Earth is greatly reduced (Topputo et al, 2015) One way for the ERV to get captured to above GEO, starting from a return orbit from Mars is via a distant retrograde orbit (DRO) around the Moon as an intermediary orbit (Lock et al, 2014). A DRO is essentially an Earth centered prograde orbit with the same orbital period as the Moon with the satellite alternating between outside of the Moon and inside of the Moon in its orbit, in such a way as to also be a Moon centered retrograde orbit.…”