Characterization of Ethylenediamine Bisborane as a Hypergolic Hybrid Rocket Fuel Additive

A boron-based catalytic and energetic fuel additive is explored as a mechanism to enhance performance of hybrid motors using nitric-acid-based oxidizers. Ethylenediamine bisborane is highly hypergolic with nitric acid, thereby eliminating the need for a separate ignition system and providing the potential for restart. Ignition delays of 2.9±0.3 ms for ethylenediamine bisborane powder and 31.7±19.6 ms for ethylenediamine bisborane/hydroxyl-terminated polybutadiene combinations have been measured using white fuming nitric acid as the oxidizer. Theoretical specific impulse values higher than any other nitric-acid-based hypergolic hybrid combination tested are obtained; in addition, ethylenediamine bisborane is air stable and not toxic. Also presented is a method of manufacturing large quantities of high-purity ethylenediamine bisborane.