Hypergolic Characterization of HAN-Based Ionic Liquids for Propulsion and Gas Generating Systems
Open Access
- Author:
- Over, Dillon
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 25, 2024
- Committee Members:
- Richard A Yetter, Thesis Advisor/Co-Advisor
Jacqueline Antonia O'Connor, Committee Member
Mary Frecker, Program Head/Chair - Keywords:
- HAN
Hydroxylammonium Nitrate
Hybrid Rocket
Hypergolic Ignition
Ignition Delay
Ionic Liquid
Green
Green Oxidizer
Nitric Acid
Hydrogen Peroxide - Abstract:
- Hypergolic formulations, materials that are capable of spontaneous ignition when brought into contact with one another, are of high importance in the aerospace industry as fuels and propellants due to the simplicity they can bring to propulsion systems. Current hypergolic propellant formulations used are toxic, often carcinogenic, and can possess storability issues due to their high vapor pressure. Propellants based on hydroxylammonium nitrate (HAN), and high-test hydrogen peroxide (HTP) can be less toxic compared to these conventional storable liquids used in hypergolic propellant. Considered as environmentally friendly, green, liquids, dense oxidizer formulations based upon HAN and HTP have the potential to replace traditional toxic monopropellants (e.g., hydrazine) or oxidizers [e.g., nitrogen tetroxide/mixed oxides of nitrogen (MON) or nitric acid]. Unlike hydrazine, formulations of HAN and hydrogen peroxide also do not possess issues of high vapor pressure and have lower freezing points compared to conventional hypergolic liquids. This thesis examines solid material reactivity response to various green HAN-based oxidizer formulations. From all powders tested, lithium aluminum hydride, sodium aluminum hydride, sodium amide, and sodium hydride showed best reactivity with HAN based oxidizer, with sodium amide showing the lowest ignition delay of 1 ms. Partially decomposed HAN via electrolysis provided a more reactive oxidizer which lowered the delays on all powders. Compound mixtures were tested for ignition delay and reactivity levels with OXSOL 1 and 13M HAN. 25 wt% of highly reactive sodium hydride, sodium amide, and lithium aluminum hydride were mixed with less reactive compounds to investigate the reaction and ignition enhancement and possible synergistic effects. The ignition delay of lithium aluminum hydride with 13M HAN could decrease significantly with just a 5 wt% additive of sodium hydride or sodium amide. Pressed pellets of neat lithium aluminum hydride and sodium amide showed similar reactivity as loose powder and continued to react over a longer time. Pressing of lithium aluminum hydride poses challenges due to its friction sensitivity, limiting the size of the pellet and increasing hazards. Consolidation of the hypergolic powders, such as lithium aluminum hydride and sodium borohydride, was successful through a casting technique. This technique used polypropylene or polyethylene as a binder with toluene as a casting solvent. This mixture of binder, solvent, and hypergolic powder would be cast, and the solvent would be allowed to vaporize off. This resulted in a hypergolic pellet that still ignited with 13M HAN and OXSOL, with slightly less reactivity.