Foam-Based Ignition System for Non-Toxic Propellants

Hydroxylammonium nitrate (HAN)-based propellant promises many improvements over hydrazine and NTO/MMH propellants. Chief among these is improved safety, which will significantly decrease overall use costs. However, reduced toxicity monopropellants are difficult to ignite. Although this characteristic is an asset for safety, it is a liability for design. Before HAN-based propellants can be commercialized, a reliable ignition system must be established. Ultramet has completed several projects for DoD and NASA directed toward the development of an ignition system for HAN-based monopropellants that have led to many key advances. The goal of the proposed effort is to reliably ignite HAN-based monopropellants by using a variation of resistojet technology based on resistively heating Ultramet foam. Ultramet will develop an ignition system consisting of open-cell foam made of refractory materials that can be heated resistively and can then transfer thermal energy to the propellant stream to initiate decomposition. Ultramet will characterize the electrical and thermal characteristics of several refractory foams and demonstrate ignition characteristics using spot plate testing and hot-fire testing on test engine sizes appropriate for kinetic kill vehicle divert and attitude control system and microsatellite attitude control system applications. In follow-on work, pino testing, macrodifferential thermal analysis, and additional hot-fire testing would be performed.