Fuel-Flexible Spacecraft Electric Propulsion System

Spacecraft electric propulsion (EP) systems typically rely on noble gas fuels (xenon, krypton, argon) stored in high pressure tanks. These fuels are unattractive for sustained ambient-air operation in very Low Earth Orbit (vLEO), or for liquid refueling operations in higher orbits using water or chemical rocket fuels as output propellants. Furthermore, thruster development to date has been highly specific to individual fuels, requiring costly development of entirely new systems for new propellants—for example, optimizing for air in a vLEO environment versus water in a possible future higher orbit refueling architecture. These dependencies limit total propulsive capability and overall mission flexibility and responsiveness. This topic seeks a system able to operate on air (20-50% O2, balance N2), water (H2O), mixtures of water and carbon dioxide (CO2) derived from combusted hydrocarbons, or nitrogen-hydrogen mixtures derived from decomposed NH3 (ammonia) or N2H4 (hydrazine), using as much shared componentry as possible. Developing a flexible fuel EP system capable of accepting a variety of molecular propellants offers a unique capability for a single product line to serve a significantly larger mission space and total addressable market. This STTR topic seeks to develop a complete, integrated fuel-flexible propulsion system that bridges the gap between laboratory demonstration and fieldable spacecraft technology capable of utilizing in-situ resources.