Mars Ascent Vehicle Hybrid Motor Development Testing

The Jet Propulsion Laboratory (JPL) is designing a Mars Ascent Vehicle (MAV) as part of a potential Mars Sample Return mission to boost collected samples from the surface to Mars orbit for eventual return to Earth. Due to some unique requirements for high performance, storability and survivability at low surface temperatures, JPL has selected a unique hybrid motor for single stage to orbit boost propulsion. The 6,050 N (1,360 lb) thrust hybrid rocket motor will be fed with MON30 as the oxidizer and will burn a specialized formulation of a paraffin fuel named SP7 in a single circular port configuration. Total burn time is slated to be ~115 seconds. This paper presents the recent development of four full-scale MAV motors at Whittinghill Aerospace. Propulsion testing began with MON03. Burn times have ranged from 20 to 90 continuous seconds, including an automated two-burn ascent profile consisting of a 85 second burn, shutdown and 15 second delay, followed by a 5 second “orbit injection” burn. The motors have demonstrated good stability and combustion efficiency throughout the burn. Two of the motors featured liquid injection thrust vector control with MON03 as the injectant. The figures of merit of Isp, c* efficiency, side Isp, SP7 regression and mechanical performance, fuel utilization, and throat erosion were evaluated. The test results are very encouraging, and point to a viable propulsion solution for the MAV.