AIAA-2015-3867 Effect of Water and Humidity on Hypergolic Propellant Ignition Delay
Figure 1. Representation of the steps identified in MMH/WFNA hypergolic ignition 7 Alternatively, the types of reactions that control the hypergolic ignition with WFNA can be identified as acid- base neutralization, nitration, and oxidation reactions Neutralization reactions begin to occur immediately upon propellant contact. These reactions generally are single step reactions that have low activation energies and release substantial heat. This helps to rapidly vaporize the propellants and starts the ignition process. 8 It is generally believed that nitration reactions only play a minor role in hypergolic ignition because they are relatively slow. However, nitration of organic compounds can lead to explosive products The decomposition to nitrogen is also highly exothermic. Due to these factors, nitration may setup some of the compounds that are critical to ignition. Oxidation at high temperatures leads to highly exothermic, runaway reactions. Although the reactants and products of complete hypergolic combustion are typically understood, the intermediate species and reaction pathways are not well known.
