Development and Test of a Highly Energetic AlH3 Difluoramino Propellant

摘要

The object of this program was to combine the difluoramine binder with the AlH3 to produce a propellant having high theoretical impulse and high efficiency. The goal of this effort was to demonstrate a practical propellant having a delivered I superscript 15 sub 1000 of 270 sec and a density of 0.061 lb/cu in. Two polymers were considered for use with the difluoramine plasticizer, TVOPA, on this program. The hydroxyl terminated polyester, Multron R-18, cured with isocyanates, produced the desired combination of mechanical properties, pot life, and low temperature cure rate. The use of a scavenger of HF was found to be necessary for long shelf life. An extensive program was conducted to determine whether the mix conditions would affect the shelf life of the TVOPA/AlH3 propellants. Stripping of an inert diluent at 140F for 16 hours reduced the gassing rate and improved the shelf life markedly. Using this mix process with a more stable AlH3, a shelf life of 5 years for large web grains stored at 70 F may be feasible. In process hazards studies indicate that the AlH3 creates some unusually hazardous conditions. Through the use of a nonvolatile coolant, such as glycerin, and prevention of contact of the blade with hard surfaces, the cured propellant can be safety machined. Ballistic testing of the TVOPA/AlH3 propellant system included the evaluation of a number of ingredient variations on the delivered impulse and burn rate. Three formulations were selected for testing in 5-pound motors. In the 5-pound motor firings, the VML (5:1 TVOPA: polymer ratio, no HMX) propellant delivered as high an impulse as the more energetic compositions so it was chosen for scaleup.