Chemical Propulsion Systems for Low Cost Mars Sample Return

Abstract

The European Space Agency (ESA) instigated the Aurora Exploration Programme in 2001. A cornerstone of the initial robotic phase of Aurora is Mars Sample Return, MSR. ESA has designed the first iteration of a ‘minimal complexity’ (and cost) MSR mission centred around a dual Ariane V launch in 2011. Mission elements include an Orbiter, including an Earth return capsule, which will launch to Mars in mid 2011. A separate descent module / Mars ascent vehicle composite will launch direct to Mars later in 2011. A Descent Module (DM) will slow the composite to a controlled soft landing near the Mars equator, and will provide a science package, sample collection arm and supporting platform functions such as power during a 14 week surface stay. A two stage Mars Ascent Vehicle (MAV) will then launch a 0.5kg sealed Mars sample onto a rendezvous trajectory with the awaiting Orbiter. A combination of 3-axis control on the MAV upper stage and Orbiter propulsion will enable sample capture by the Orbiter, transfer to the upper stage and Earth Return Vehicle for launch back to Earth, arriving in 2014. This paper critically examines the demanding propulsion requirements of the Orbiter, DM and MAV mission elements for the ESA MSR mission. Suggested solutions from the inventory of European and non-European engines have been identified and are outlined. The Orbiter requires a high reliability high Isp engine of around 800N thrust and at least 50 restarts to minimise propulsive losses on the ~4ton platform during deceleration into Mars orbit. The DM system is required to perform close loop regulation of a retro rocket system from measurements of approach velocity. A total thrust of 8000-10000N has been estimated, with an engine capable of throttling to ~10% of maximum thrust with a rapid response time, an Isp requirement has not been determined. The DM thrust depends on the MAV, two MAV’s of differing complexity and mass are being studied by major European contractors. The MAV engine will have a thrust requirement of between 2750 and 5500N, depending on the design selected. A comparable Isp to the Orbiter, in excess of 310s, is common to both, as is the survival a 14 week surface stay. All engines are intended to use storable liquid propellants.