27 th ICDERS July 28 th – August 2 nd , 2019 Beijing, China Correspondence to: cdillier2301@tamu.edu 1 Aluminized and Non-Aluminized AP/HTPB-Composite Propellant Burning Rates at Very-High Pressures Catherine A. M. Dillier, Thomas Sammet, Felix A. Rodriguez, Erica D. Petersen, James C. Thomas and Eric L. Petersen J. Mike Walker ’66 Department of Mechanical Engineering, Texas A&M University College Station, Texas, USA 1 Introduction Solid propellants are composed of either homogeneous or heterogeneous mixtures of fuel and oxidizer. Composite solid propellants can be tailored, particularly the burning rate, for specific applications through the inclusion of additives or by modifying the oxidizer average particle size. Over a limited range of pressures, the burning rate for ammonium perchlorate (AP)-based solid propellants is often described by the Saint Robert-Vielle law, Eqn. 1, where r is the burning rate, P the pressure, and a and n are experimentally determined coefficients. This burning rate-pressure relationship begins to break down however at very high pressures when the pressure exponent, n, drastically increases and the burning rate exhibits a “slope break” or “exponent break”, as referred to henceforth in the current study. This exponent break occurs at some characteristic pressure, P * , which typically lies above 14 MPa (2000 psi) for AP-based propellants [1].  =   (1) As shown in Table 1, very-high-pressure testing has been conducted before [1-8]. Most of these studies however investigated the deflagration characteristics of pure AP only. While additional high-pressure studies with AP-based propellants have been performed in government research laboratories, Table 1 demonstrates the limited amount of burning rate data available for composite AP/HTPB-based propellants in the open literature. Many strand burner facilities are capable of determining composite propellant burning rates, but most of these only test regularly up to about 15.5 MPa (2250 psi). Few burning rate data exist for higher pressures and almost none for pressures exceeding 34.5 MPa (5000 psi). As a result, most studies fail to capture the exponent break phenomenon. Therefore, the objective of this study was to expand the burning rate pressure range for aluminized and non-aluminized AP/HTPB-composite propellants up to 68.9 MPa (10,000 psi). This paper presents the results of these new data, with emphasis on ballistic curve exponent changes at these extreme pressures.