Burn-Rate Investigations of HAN-Based Candidate Liquid Propellants

Abstract

Abstract : High-pressure windowed strand burners have been used to obtain burning rates for some hydroxyl ammonium nitrate (HAN) liquid propellants over the pressure range from about 10 to 300 MPa. Measured linear burn rates for these liquids were erratic due to the manifestation of surface irregularities. This burning surface variable has been minimized by gelling. A pressure break occurs around 80 MPa for these gelled propellants. The burn rate (r) vs. pressure (p) can be adequately expressed by an exponential of the form r = Ap(exp n). For pressures below 70 MPa, n ^ 0.2, and for pressures between 70 and 300 MPa, n ^ 1.1. One HAN-based liquid propellant, XM46, has been investigated as a function of temperature as well. Due to the substantial increase in viscosity, cold-temperature (^ -50 deg C) burn rates were obtained without the use of any gelling agent These cold temperature burn rates are slightly lower than the ambient temperature rates and follow a similar pressure behavior at pressures above about 30 MPa. Hot-temperature (^ +60 deg C) gelled XM46 burn rates are slightly larger than the ambient-temperature rates, again with a similar pressure behavior. Burn rates were also determined for gelled 9.1 M HAN through the 70-MPa pressure region, but no convincing evidence of a similar pressure break was observed.