DEVELOPMENT OF AN ADVANCED ELECTROMAGNETIC GUN BARREL

An advanced electromagnetic gun (AEMG) barrel was developed for the Air Force Wright Laboratory (Armament Directorate) (WL/MN) to repetitively accelerate large mass projectiles. The AEMG barrel employed 5-m rails, had a 50-mm square bore, and was designed to operate at a peak current of 1.5 MA (bore pressure 25 ksi). Key technical achievements included (1) an efficient barrel containment structure that weighs approximately 25% of a similarly rated clamped barrel, (2) an insulator material that retains surface resistivity after repeated firings, and (3) a high-velocity water cooling system designed to remove a peak heat flux of 5 MJ/m2 per shot. The AEMG barrel's thermal management system employed a high-pressure (500 psi) blowdown system that generated high velocity coolant flow rates in five axial coolant channels within each rail. Innovative fabrication processes used to develop the barrel included: (1) the ''gun-drilling'' of small diameter axial coolant passages in the copper rails, (2) electron-beam welding of rail segments to form continuous 5-m rail lengths, and (3) preloading the barrel uniformly by injecting high-pressure epoxy between the bore components and an outer filament-wound containment tube. A 2-m prototype of the AEMG barrel was tested in General Atomics 4 MJ electromagnetic launcher test facility.