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Current programs are aiming to develop reduced toxicity monopropellant formulations to replace spacecraft hydrazine monopropellant. The Air Force Research Laboratory's (AFRL's) approach to replacing hydrazine is the synthesis and development of energetic compounds/formulations with substantially less vapor toxicity and superior performance (specific impulse and density). Characterization and testing of these high energy density materials is an essential part of the screening process for viable advanced propellants. Hazardous handling characteristics, undesirable physical properties or unacceptable sensitivity behaviors must also be identified and/or modified to further development by a potential user. AFRL has successfully identified a novel monopropellant (designated AF-M315E) that shows great promise as an avenue toward replacement of hydrazine monopropellant for spacecraft propulsion. Hazard and safety/sensitivity, stability, and toxicity studies have been conducted on the monopropellant and will be described. The results from AF-M315E indicate that a >50% improvement in propulsion system performance over hydrazine is achievable while simultaneously providing a safer environment for the general public, ground personnel, crews and flight participants., For presentation at the International Association for the Advancement of Space Safety Conference (4th) to be held in Huntsville, AL on 19-21 May 2010.

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.), Paper presented at the Int'l Conference on Green Propellant for Space Propulsion held in Noordwijk, The Netherlands, on 20 Jun 2001. Prepared in collaboration with Engineering Research and Consulting, Inc., Edwards AFB, CA.

AFN has demonstrated acceptable properties to further propellant development: displayed good stability (thermal, friction, impact and detonability), low melt point is suitable for monopropellant applications, and extremely low toxic vapor concentrations. AFN based propellant has been evaluated to indicate additional development is warranted: high performance demonstrated in thruster test bed, acceptable safety properties and low toxic vapor concentrations.