Velocity limiting magnetohydrodynamic effects in railgun plasma armatures

The results of a four-year theoretical and experimental research program in railgun armature physics at the University of Tennessee Space Institute are reviewed with an emphasis on understanding how the magnetohydrodynamic (MHD) flowfield and electromagnetic interactions limit the velocity in plasma and hybrid armature railguns. The understanding of the 3D plasma armature flowfield has been developed through a combination of highly instrumented railgun experiments, secondary arc performance models, and 2D MHD calculations. These 2D calculations are only qualitative in nature, but they provide insight into the complex armature flow and indicate that the formation of secondary armatures, ablation drag, and primary armature preparation are interrelated. Experimental evidence suggests that 3D MHD flow effects are very important in controlling these phenomena