The use of onboard rocket propellants (dense liquids at room temperature) in place of conventional cryogenic fuel-cell reactants (hydrogen and oxygen) eliminates the mass penalties associated with cryocooling and boil-off. The high energy content and density of the rocket propellants will also require no additional chemical processing.
For a 30-day mission on the Moon that requires a continuous 100 watts of power, the reactant mass and volume would be reduced by 15 and 50 percent, respectively, even without accounting for boil-off losses. The savings increase further with increasing transit times. A high-temperature, solid oxide, electrolyte-based fuel-cell configuration, that can rapidly combine rocket propellants — both mono-propellant system with hydrazine and bi-propellant systems such as monomethyl hydrazine/ unsymmetrical dimethyl hydrazine (MMH/UDMH) and nitrogen tetroxide (NTO) to produce electrical energy — overcomes the severe drawbacks of earlier attempts in 1963–1967 of using fuel reforming and aqueous media. The electrical energy available from such a fuel cell operating at 60-percent efficiency is estimated to be 1,500 Wh/kg of reactants. The proposed use of zirconia-based oxide electrolyte at 800–1,000°C will permit continuous operation, very high power densities, and substantially increased efficiency of conversion over any of the earlier attempts. The solid oxide fuel cell is also tolerant to a wide range of environmental temperatures. Such a system is built for easy refueling for exploration missions and for the ability to turn on after several years of transit. Specific examples of future missions are in-situ landers on Europa and Titan that will face extreme radiation and temperature environments, flyby missions to Saturn, and landed missions on the Moon with 14 day/night cycles.
This work was done by Gani Ganapathi and Sri Narayan of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Physical Sciences category. NPO-44977
This Brief includes a Technical Support Package (TSP).
Fuel-Cell Power Source Based on Onboard Rocket Propellants
(reference NPO-44977) is currently available for download from the TSP library.
Don't have an account?
Overview
The document outlines a project led by S. R. Narayan and Gani Ganapathi at NASA's Jet Propulsion Laboratory (JPL) focused on developing a high energy density fuel cell power source that utilizes onboard rocket propellants. The primary objective is to demonstrate the feasibility of this innovative power source for space missions requiring substantial power over extended durations, such as in-situ landers on Europa and Titan, flyby missions to Saturn, and lunar missions with long day/night cycles.
The proposed fuel cell will leverage existing propulsion tanks containing monomethyl hydrazine (MMH), unsymmetrical dimethyl hydrazine (UDMH), and nitrogen tetroxide (NTO). By combining these reactants in a controlled manner, the fuel cell aims to produce electricity with an estimated efficiency of 60%, yielding approximately 1500 Wh/kg of reactants. This approach offers significant advantages over traditional power sources, such as primary batteries and radioisotope-based systems, which can be too heavy or costly for long-duration missions.
The project is structured over two years. In the first year, activities will include materials selection, cell design, performance studies in a single cell configuration, fuel feed and thermal design, and safety considerations. The second year will focus on demonstrating a laboratory power source system capable of producing between 10 to 50 Watts.
One of the key innovations of this project is the use of dense liquid rocket propellants at room temperature, which eliminates the challenges associated with cryogenic fuel cell reactants, such as cooling and boil-off losses. The high energy content and density of these propellants will lead to significant mass and volume savings, particularly for missions requiring continuous power over extended periods. For instance, a 30-day lunar mission requiring 100 Watts could see a reduction in reactant mass and volume by 15% and 50%, respectively.
The development of this fuel cell power source represents a significant technical advancement for JPL, enabling mission designers to extend mission durations and enhance scientific returns from short-lived landed and flyby missions. This initiative also reinforces JPL's leadership in the field of fuel cell technology for space applications. For further inquiries, contact information is provided for JPL's Innovative Technology Assets Management.
