High Energy, Low Temperature Gelled Bi-Propellant Formulation for Long-Duration In-Space Propulsion

Development of a candidate bi-propellant system consisting of a gelled hydrocarbon fuel coupled with a highly energetic gelled oxidizer suitable for outer planetary missions is proposed. Theoretical calculations suggest that this innovative combination can meet NASA's propulsion requirements for low power consumption (i.e. minimal use of heaters) while providing a vacuum specific impulse of ~ 360 seconds. Gelling the propellant provides the advantage of higher volumetric efficiency and suspending energetic fine particulates (e.g. boron, carbon, or aluminum) increases the energetic yield. Furthermore, gels do not spread if spilled and have greatly reduced vapor pressure making their handling far less hazardous, compared to current spacecraft fueling procedures that employ highly toxic liquid hypergols. The Phase I program objectives will include the 1) formulation of gel propellant fuel samples, 2) measurement of their rheological properties as a function of temperature, 3) simulation of a gel-fueled thruster propellant flow network using NASA's GFSSP code, and 4) high-fidelity simulations of the gel propellant tank expulsion process at outer planet equilibrium temperatures. The Phase II will include further properties assessments, high-fidelity simulations of the bi-propellant combustion process followed by experimental gel thruster test and evaluation. This innovation will improve the safety, operability reliability, and performance of in-space propulsion systems and extend the existing technology base for human and robotic exploration missions.