Characterization of Reduced Toxicity, High Performance Monopropellants at the U.S. Air Force Research Laboratory

Abstract : Current U.S. Air Force programs are working to develop reduced toxicity monopropellant formulations to replace spacecraft hydrazine monopropellant and exceed the monopropellant performance objective (greater than 50% increase in density impulse) specified by the Integrated High Payoff Rocket Propulsion Technology (IHPRPT) Program. The creation of such monopropellants can offer considerable cost savings associated with handling and loading, longer spacecraft service life, smaller vehicle design, and heavier payloads. The Air Force Research Laboratory's (AFRL) approach to replacing hydrazine is the development of energetic liquid salt mixtures with substantially less vapor toxicity and superior performance (specific impulse and density). These liquid salt mixtures show promise as one avenue toward replacement of hydrazine monopropellant. During the last year, work has centered on the production and characterization of a few of these reduced toxicity monopropellant formulations. Aside from a low melting point and toxicity, there are a number of properties that are desirable for a monopropellant successor to hydrazine. This report presents the results of tests of specific properties of a new monopropellant (AFN1) that is under investigation by AFRL and compared them to hydrazine. Experimental results are provided for density, vapor toxicity, carbon content of exhaust, melting point, detonability, friction and impact sensitivity, Adiabatic compressibility, thermal stability, critical diameter, viscosity, velocity, and theoretical performance with regard to specific impulse, density, volumetric impulse, and detonation velocity. The report also provides thruster test results for AFN1 and hydrazine in the following areas: theoretical, measured, and efficiency of catalytic decomposition at 64% ammonia dissociation; chamber pressure; throughput; and pulse duration. (6 tables, 2 figures, 5 refs.)