Title of Presentation:  Pump Fed Propulsion for Mars Ascent and Other Challenging Maneuvers

Primary (Corresponding) Author:  John Whitehead

Organization of Primary Author:  Lawrence Livermore National Laboratory

Abstract: High-pressure pump-fed rocket cycles greatly reduce the mass of both tanks and engines, while offering an increase in specific impulse.  Launch vehicles rely on this principle routinely, because it enables high delta-V maneuvers in a few minutes.  Science can also benefit from implementing pump-fed propulsion technology on a small scale to achieve more with limited resources, including missions that have never been done.  Mars Sample Return is a prime example, because ascending from Mars to orbit requires a miniature launch vehicle.  Another aggressive launch-like maneuver is needed to depart Mars orbit and reach Earth.

The technology also makes sense for reducing the weight of Mars descent propulsion, in order to increase the science payload on future landers.  Other potential applications include visiting the moons of Earth and the outer planets, e.g. descent to the surface of Europa.  A miniature launch vehicle might enable a Venus atmospheric sample return mission.  A Mars airplane powered by rocket propellants could have unpressurized wing tanks, for a higher fuel fraction and a greater range.

From 2004 to 2006, NASA's Mars Technology Program funded the development and successful testing of a miniature propellant pump at the Lawrence Livermore National Laboratory.  A pair of the 300-gram pumps would deliver oxidizer and fuel from low-pressure tanks to above 800 psi.  Demonstrated flow is sufficient for 1000-N thrust, as needed for a 100-kg Mars Ascent Vehicle (MAV).  By permitting a compact, high-pressure engine to be fed from lightweight 50-psi tanks, the unique pump technology results in propellant mass fractions near 90 percent, unheard of on a small scale.  The measured consumption of high-temperature (900 F) gas that powered the pump is sufficiently low that a net increase in specific impulse is expected.

A complete technology development effort requires testing the pump with propellants, and a compact high-pressure thrust chamber.  Pump-fed system testing is needed to verify and tune the gas generator circuit, which derives energy from a few percent of the fuel to power both the oxidizer pump and the fuel pump.  The resulting technology would then be packaged as a lightweight integrated rocket stage for mission applications.