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N2O/O2 blends safe and volumetrically efficient oxidizers for small spacecraft hybrid propulsion


Aeronautics and Aerospace Open Access Journal
Stephen A Whitmore,1 Robb L Stoddard2

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Abstract

A medical grade nitrous oxide and gaseous oxygen fluid blend, “Nytrox,” is investigated as significantly safer, but superior performing, alternative for the current generation of environmentally unsustainable spacecraft propellants. In a manner directly analogous to the creation of soda-water using dissolved carbon dioxide, Nytrox is created by bubbling gaseous oxygen under high pressure into nitrous oxide until the solution reaches saturation level. Oxygen in the ullage vapor dilutes the nitrous oxide vapor and increases the required decomposition activation energy of the fluid by several orders of magnitude. Consequently, any risk of inadvertent thermal or catalytic decomposition is virtually eliminated. This paper reports on a preliminary test-and-evaluation campaign where an existing small spacecraft thruster is first tested using gaseous oxygen and 3-D printed ABS as propellants as a baseline. The baseline tests were then repeated using an optimized Nytrox bend as “drop-in” replacement for gaseous oxygen. Test parameters compared include; ignition reliability and required energy, thrust coefficient, characteristic velocity, specific impulse, and fuel regression rate. Nytrox is shown to work effectively and reliably as a replacement for gaseous oxygen, exhibiting a slightly reduced specific impulse and regression rate, but with significantly higher volumetric efficiency. Recommended topics for future research are discussed.

Keywords

hybrid rocket, “Green” propellants, nitrous oxide decomposition, energy of activation, 3-D printing, Nytrox

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