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

Abstract

A medical grade nitrous oxide (N2O) and gaseous oxygen (GOX) “Nytrox” blend is investigated as a volumetrically-efficient replacement for GOX in SmallSat-scale hybrid propulsion systems. Combined with 3-D printed acrylonitrile butadiene styrene (ABS), the propellants represent a significantly safer, but superior performing, alternative to environmentally-unsustainable spacecraft propellants like hydrazine. In a manner analogous to the creation of soda-water using dissolved carbon dioxide, Nytrox is created by bubbling GOX under pressure into N2O until the solution reaches saturation. Oxygen in the ullage dilutes N2O vapor and increases the required decomposition energy barrier by several orders of magnitude. Thus, risks associated with inadvertent thermal or catalytic N2O decomposition are virtually eliminated. Preliminary results of a test-and-evaluation campaign are reported. A small spacecraft thruster is first tested using gaseous oxygen and 3-D printed ABS as the baseline propellants. Tests were then repeated using Nytrox as a “drop-in” replacement for GOX. Parameters compared include ignition reliability, latency, initiation energy, thrust coefficient, characteristic velocity, specific impulse, combustion efficiency, and fuel regression rate. Tests demonstrate Nytrox as an effective replacement for GOX, exhibiting a slightly reduced specific impulse, but with significantly higher volumetric efficiency. Vacuum specific impulse exceeding 300 s is reported. Future research topics are recommended.

Testing of the N2O/HDPE Vortex Flow Pancake Hybrid Rocket Engine with Augmented Spark Igniter

“…From the short list of green oxidizers, N 2 O and HTP (hydrogen peroxide) appear to be the most practical options for space propulsion [30]. Recently Nytrox (a mixture of O 2 and N 2 O) was proposed [3,31] to enhance N 2 O performance and safety, but it requires temperatures below 0 • C, thereby excluding it from the category of storable propellants. Although HTP offers potentially higher specific impulse and storage density compared to the systems based on the N 2 O, the latter seems to achieve significant market traction as a green chemical propulsion replacement [32].…”

“…However, these ionic liquid-based propellants, while less toxic than hydrazine, are not environmentally friendly and are harmful to organic tissue. Ionic liquid-based propellants also require catalyst bed preheating to more than 340-370 • C due to their high-water content, as pointed out by Whitmore [3]. This preheating requirement increases system complexity, dry mass, and power consumption, making them unsuitable for small spacecraft.…”

Test Activities on Hybrid Rocket Engines: Combustion Analyses and Green Storable Oxidizers—A Short Review

“…For hydrogen peroxide, two different concentrations are considered: 90 wt.% and 98 wt.%. As reported by Whitmore [95], the use of H 2 O 2 with a concentration >90 wt.% makes the definition of a green propellant only slightly applicable (see also [96]). However, high concentrations of hydrogen peroxide are typically accepted as green reactants.…”

In-Situ Optical Measurements of Solid and Hybrid-Propellant Combustion Plumes

“…This fuel rich operation, coupled with the noted combustion inefficiencies, resulted in flame-temperatures and specific impulse values that are lower than have been previously achieved for GOX/ABS combustion. (Whitmore [25]) The fuel rich operation also limited any effects due to nozzle erosion during the burn.…”