Effect of Complex Metal Hydrides on the Elimination of Hydrochloric Acid Exhaust Products from High-Performance Composite Solid Propellants: A Theoretical Analysis

Ammonium perchlorate (AP)-based solid rocket propellants generate hydrochloric acid (HCl) as an exhaust product during combustion. This latter displays numerous environmental problems such as the depletion of the ozone layer and the increase of the concentration of acid rains. This paper offers a theoretical analysis concerning the employment of metal hydrides as efficient additives to mitigate some of the negative effects of HCl on the environment during the combustion of AP-based composite propellants. Nine complex metal hydrides, expected to generate desirable performance gains, are selected to assess their scavenging effect on the HCl during propellant combustion. Based on NASA Lewis Code, Chemical Equilibrium with Application (CEA), comparative analysis of the theoretical performance of specific impulse, adiabatic flame temperatures, condensed combustion products as well as the exhaust gaseous species has been carried out. This study reveals that complex metal hydrides-based propellants exhibited better performance than those containing simple metal hydrides, showing a synergetic effect of high specific impulse and low environmental impact. It is consequently anticipated that a good choice of metal hydride can provide clean/green propellant formulations that can satisfy the current environmental requirements with better performance than current aluminum propellants.