An Experimental Study of the Relative Sensitivity to Oxidative Aging of NaBH ₄ ‐promoted Green Hypergolic Fuels

ABSTRACT Conventional hypergolic propellants cause technical problems due to their toxicity and carcinogenic properties, which increase development costs and lead to significant environmental issues. These challenges can be addressed by incorporating additives with low‐toxicity fuels to render them hypergolic. It is necessary to approach the storage stability challenges associated with these low‐toxicity hypergolic propellants. In this study, the storage characteristics of a NaBH 4 ‐promoted hypergolic fuel were investigated. A reactive fuel was prepared by dissolving 4 wt.% sodium borohydride as the ignition agent. Fuel stability tests were performed in air, dry air, nitrogen, and vacuum to determine oxidation effects. Tests were also performed at relative humidity levels of 10%, 40%, and 80% to analyze the effect of moisture on the degree of fuel oxidation. The degree of fuel deterioration was evaluated based on changes in density, viscosity, chemical composition, and ignition performance. The relative influence of oxygen on fuel deterioration was confirmed in the order of air > dry air > nitrogen > vacuum. Fuel deterioration accelerated with increasing relative humidity. NaBO 2 was the main sediment, and the degree of oxidation was more pronounced with moisture than with oxygen.