Combustion characteristics of low flame temperature, chlorine-free composite solid propellants

Abstract

Presently, there is an increased interest in composite solid propellants that burn with low flame temperatures and do not contain chlorine or chlorine compounds. Applications for such propellants may be found in solid propellant gas generators and turbine pump starters. Phase-stabilized ammonium nitrate (ANS)-based propellants meet these requirements, but other composite propellant formulations are also feasible, such as propellants based on a rubber binder and nitroglycerin (NG) or trimethylol-ethane-trinitrate (TMETN). In order to compare the combustion characteristics of these propellants, three different families have been developed and tested: 1) Hydroxy-terminated polybutadiene (HTPB) binder with ANS and various catalysts; 2) Polyester-urethane (PU) binder with NG and nitroguanidine (NQ) or guanidine nitrate (GuNi); and 3) PU binder with TMETN and NQ or GuNi. With some exceptions, all propellant formulations have calculated flame temperatures between 1200 and 1400 K. In a special burner, the combustion characteristics of these propellants have been investigated in the pressure region between 1 and 10 MPa. The results of this study show that burning rates up to 7 mm/s at 10 MPa may be obtained, while the burning rate exponent may vary between 0.3 and 0.7. In addition, the importance of catalysts to improve the ignitability of (ANS)-based propellants is confirmed.