Theoretical Approach to 1 Amp/1 Watt, No-Fire Ordnance Designs

A heat transfer analysis has been made of a typical ordnance header to derive the relationship between the various parameters which determine thermo-dissipative characteristics of the device. Because of the complex geometries and the large number of parameters involved, the solution to this general problem has long been regarded as too complex for direct solution. It has been shown that an equation may be greatly simplified and the number of parameters reduced to eight important ones so that the problem can be programmed for solution by a computer. The program yields temperature distributions as a function of both space and time and for time periods appropriate to the all-fire and the no-fire test conditions, i.e., milliseconds or five minutes. The solutions of the equation have been checked by over 400 firings with various header geometries, materials, and firing currents and found to be quite accurate. The solutions allow one to design ordnance hardware to have a wide range of all-fire characteristics for any designated no-fire characteristic. They also make it possible to predict the changes in ordnance design necessary to increase the no-fire characteristic from present one watt levels to 2, 5, or 10 watt no-fire levels.