Plasma Armature Railgun Launcher Simulations
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The Center for Electromechanics at the University of Texas (CEM- UT) at Austin has developed a velocity dependent friction model which accurately predicts the losses associated with a plasma armature railgun while performing research associated with several Defense Advanced Research Projects Agency (DARPA) contracts. Test results from CEM-UT's 1 m long, 1.27 cm square bore, plasma-armature railgun have been used to determine the validity of the model. Deviation between calculated and measured performance is typically less than 5% at railgun currents below 500 kA, however, at currents greater than 500 kA, the deviation increases. Experimental evidence suggests that the rail gun' s lack of stiffness and subsequent venting of driving pressure rather than the electromechanical model is primarily responsible for the divergence between predicted and measured results. To test this theory a railgun was built using external preloading rings (Ringfeder®) to increase its stiffness. On the first test of the Ringfeder® railgun, 700 kA was discharged into the gun and the projectile was accelerated to 5.9 km/s. Test data indicates that the projectile accelerated through the entire length of the railgun and that a minimum amount of plasma leakage had occurred during the test. An analysis of the 700-kA test was done to compare the results of CEM-UT's frictional loss model to ablation and viscous drag loss models.