Advanced Propellant Pressurization System

Spacecraft frequently use pressurized helium for propellant tank pressurization, which while safe and effective carries a weight penalty that becomes burdensome as tank size increases. In this project, Ultramet will investigate pressurization systems wherein the pressurant will come from either the thermal decomposition of a solid or from the decomposition of existing liquid propellant on the spacecraft. Both approaches eliminate the need for a helium reservoir. In one approach, a solid will fill the pores of an electrically heated monolith of ceramic foam, and gas will be generated on demand by passing electricity through the foam to thermally decompose the solid. An endothermic solid will be used so the system cannot undergo thermal runaway. In the other approach, small volumes of propellant will be fed into a small reaction vessel filled with electrically heated foam. In both approaches, the resulting gases will be fed into the pressurant side of the propellant tank to provide pressurization. Such systems will reduce the mass relative to a helium-based system. Because the hardware mass for this concept is independent of propellant throughput, the benefits become more pronounced with larger spacecraft. This approach also enables tank pressure to be regulated for reduced impulse variability.