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

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.

Nytrox as “Drop-in” Replacement for Gaseous Oxygen in SmallSat Hybrid Propulsion Systems

“…Thus, even though the results to be presented later in this paper consider a very small thruster system operating at low chamber pressures, the results have a wider range of applicability. (Copyright Utah State University [46], reproduced with permission).…”

“…The hot-fire testing campaign was performed inside USU's on campus hazardous test facility. Whitmore and Bulcher [1], Whitmore and Stoddard [46]], and Stoddard [50] describe the analytical methods, test apparatus, instrumentation, test procedures, and analysis methods used to derive the presented data in much fuller detail.…”

“…Density of nytrox vapor and liquid phases at vapor pressure for 7 different isotherms. (Copyright Utah State University[46], reproduced with permission).…”

“…Summary of the Nytrox 87/ABS hot-fire test results. (Copyright Utah State University[46], reproduced with permission).…”

Special Issue “Advances in Hybrid Rocket Technology and Related Analysis Methodologies”

“…Finally, the subject analyzed by Whitmore [21] in the twelfth paper, which at the moment of this foreword is still on the publication path, is the investigation into a fluid blend of nitrous oxide and gaseous oxygen as a significantly safer and higher volumetrically-efficient alternative for the current generation of environmentally-unsustainable spacecraft propellants.…”