Ignition of a Green Hypergolic Hybrid Rocket Propellant under Oxidizer Sprays

This paper describes spray ignition experiments involving a promising green hypergolic hybrid rocket propellant combination. The propellant consists of rocket grade hydrogen peroxide (RGHP) as oxidizer, highdensity polyethylene (HDPE) as fuel and sodium borohydride (NaBH4) as the energetic hypergolic additive embedded in the HDPE matrix. The setup consists of the HDPE + NaBH4 fuel sample placed under a spray nozzle. RGHP is sprayed on the fuel sample, causing ignition. High speed visible (monochrome) and infrared imaging cameras are utilized to study the ignition event. The high-speed infrared camera with a water vapor filter is used to detect presence of water vapor, likely resulting from the RGHP-NaBH4 reaction. The spray oxidizer feed configuration utilized in this work closely emulates the injection systems in actual rocket motors; as such the experiments can lead to accurate and comprehensive ignition characterization of this promising propellant combination.