As part of a global drive to move towards less toxic propellants, Nitrous Oxide Fuel Blends (NOFB) have been identified as a potential monopropellant to replace hydrazine. These have high performance and the potential to be long term storable, but little is known about their combustion performance or long-term storability in practice.
AEL were approached by TNO to perform combustion testing of a liquid nitrous oxide blend with ethanol. Due to the potential risk of explosion once the oxidiser and fuel are mixed, AEL had to design a very low volume pre-mixing chamber to mix the two liquids in real-time directly before injection into the chamber. This used an additively manufactured injector to inject the flow of ethanol into the shear layer between two counter-rotating annular streams of nitrous oxide. The project culminated with the first European firing of a liquid nitrous-oxide fuel blend.