Development of a deterred propellant for a large caliber weapon system

Abstract There is a continuing need to increase the velocity and associated terminal performance of kinetic energy ammunition as tougher armor targets are encountered. Application of a deterrent, or burning rate reducer, into the surface of standard propellants, together with appropriate changes in geometry and loading density, has been suggested as a means of increasing velocity by as much as ten percent. The attainment of such a desirable performance gain is critically dependent on the deterrent's satisfying certain requirements: (1) chemical compatability with the base propellant, (2) sufficient penetration of the base propellant, (3) diffusion stability of the deterred region over an extended time, (4) ignitability of the deterred layer, (5) sufficient decrease in burning rate. Unfortunately, there exists only a minuscule data base on the way deterrents behave when applied to various base propellants. The deterred propellants used in small arms and anti-aircraft guns were developed by a cut-and-try technique, and the sort of data required for rational design of large caliber weapons systems, e.g. burning rates in the deterred region, is extremely scarce. Since we lack an appropriate data base we have used thermochemical calculations and burning rate estimates to identify promising deterrent/base propellant combinations. The burning rate estimates were based on empirical fits to available closed bomb and strand burner tests with small arms propellants. Several promising deterrent systems are presented, including five candidates which exhibit a decrease in burning rate with no decrease in propellant energy. On the basis of these theoretical predictions, an experimental deterrent coating and analysis study has been initiated at Radford Army Ammunition Plant.