Improved Design, Fabrication, and Testing of an Ascent Vehicle Reaction Control System

Sample return missions generally have the largest velocity change (Delta;V) requirements for a mission to a given body, especially bodies with large gravity wells. For every gram of liftoff mass removed from the return vehicle, the incremental reduction in gross liftoff mass from Earth is several orders of magnitude greater. Consequently, any technology that can reduce the mass that must be lifted out of the target bodyrsquo;s gravity well will have a huge impact on the amount of mass that must be lifted off the Earthrsquo;s surface. For an ascent vehicle, regardless of whether a solid, liquid, or hybrid rocket is used, thrusters will be needed for the reaction control system. Studies have shown that above a certain threshold, monopropellant systems become more mass-efficient than cold gas systems. An in-house trade study has shown that for total impulses above 140 Nmiddot;s, a traditional hydrazine system has less mass than a cold-gas system. The same study also showed that if a foam-based ignition system is used with hydrazine instead of a granular catalyst and external heaters, the breakeven point drops to just 44 Nmiddot;s. Furthermore, as the total impulse requirement increases, the mass advantage of the foam-based hydrazine system increases significantly. In this project, Ultramet will build upon a recently completed effort in which a foam-based ignition system for hydrazine was designed, fabricated, and hot-fire tested. In particular, modifications will be made to the design to facilitate testing, and more extensive hot-fire testing will be performed.