Benefits of a Hybrid Propulsion System Using In Situ Produced Oxidizer for a Mars Ascent Vehicle

Paper number

IAC-15,C4,2,10,x30128

Author

Dr. Ashley Karp, Jet Propulsion Laboratory - California Institute of Technology, United States

Coauthor

Mr. Barry Nakazono, Jet Propulsion Laboratory, United States

Coauthor

Ms. Rebekah Tanimoto, Jet Propulsion Laboratory - California Institute of Technology, United States

Coauthor

Mr. David Vaughan, United States

Coauthor

Dr. Gerald Voecks, United States

Coauthor

Mr. Joseph Lewis, Jet Propulsion Laboratory - California Institute of Technology, United States

Coauthor

Ms. Audra Kudirka, Jet Propulsion Laboratory - California Institute of Technology, United States

Coauthor

Mr. Loren Jones, Jet Propulsion Laboratory - California Institute of Technology, United States

Coauthor

Mr. Dhack Muthulingam, Jet Propulsion Laboratory - California Institute of Technology, United States

Year

2015

Abstract

In-Situ Propellant Production (ISPP) makes hybrid propulsion especially attractive for a Mars Ascent Vehicle (MAV) that could be part of a potential Mars Sample Return (MSR) Campaign. Gaseous oxygen can be produced from the Martian atmosphere. Therefore, only the dense, hybrid fuel would need to make the trip from Earth. The paraffin/oxygen hybrid design concept being presented here optimizes in performance at a fuel to oxidizer ratio of about 2.5/1. This translates into a ~70\% propellant mass savings for the MAV. Additionally hybrids have systems benefits over traditional (solid propulsion) MAV designs. The thermal “igloo” typically required can be minimized with this design because paraffin enjoys a particularly low glass transition temperature. A hybrid MAV could also be throttled, enabling more accurate Mars orbit insertion to ease the requirements on the rest of the campaign.

The ISPP process is completed in three relatively simple steps. A low power cryocooler is used to freeze CO2 out of the Martian atmosphere. Of all the constituents in the Martian atmosphere, CO2 has the highest freezing point (about 150K at Martian surface pressure), meaning it will freeze first. The relatively pure CO2 is then allowed to warm up in a small, holding volume, where it increases in pressure. The pressurized CO2 is then passed through a solid oxide electrolysis (SOXE) unit. The SOXE unit converts the CO2 to O2 with approximately 67\% conversion efficiency. Unconverted CO2 can be passed through the SOXE again or vented. The rate of production depends on the power input into the SOXE. Roughly 50g/hr can be produced at 250W. The ISPP oxidizer can then be transferred to the MAV as high pressure, gaseous oxygen. A similar process is currently being developed for the MOXIE instrument, a Mars 2020 payload.

The merits of a hybrid system design will be presented in comparison with a solid MAV concept. The entire system will be evaluated including: the rocket itself, the hardware required for the in-situ propellant production and the thermal insulation of the system. The representative solid system is presented by scaling previous designs using CTPB-based (low temperature, Mars qualified) propellant. Residual challenges for the hybrid MAV will be discussed. As will, potential complementary benefits, such as oxygen production at Mars, which could be the first step in human exploration of the red planet. The mass savings enabled by the ISPP/hybrid MAV could enable or substantially augment a potential MSR campaign.

Abstract document

IAC-15,C4,2,10,x30128.brief.pdf

Manuscript document

(absent)