Ultra-stiff, low mass, EM gun design

High performance in an electromagnetic (EM) gun implies high velocity with minimal transition from a solid to plasma armature. Factors that affect gun performance include armature integrity, bore straightness and bore stiffness. Experiences firing solid armature at CEM-UT since 1987 have shown that the lack of one or more of these three ingredients will result in less than desirable performance. This paper presents a simple, ultra-stiff and low mass EM gun design that provides five to six times the rail-to-rail structural stiffness than a conventional bolted, composite sidewall-type EM gun construction. This translates into minimal bore deflection which lessens the amount the armature must distort to maintain a low voltage contact with the rails. The EM gun design incorporates a passive preloading mechanism that maintains a compressive stress state in the bore components without the use of hydraulics. Bore preload is provided that exceeds the maximum rail-to-rail EM loads and is reacted by a composite structure that also provides longitudinal barrel stiffness. Manufacturing techniques are presented that would allow the design to be built on a small or large scale using standard manufacturing tolerances and demonstrated assembly processes. Material selection and impact on the ability to actively cool a railgun is also presented.