ET-guns with working media of low molecular weight: a numerical study

Numerical simulations of the electrothermal acceleration process have been carried out in order to assess the potential of different working media. For some interesting substances, the mass/energy ratio and the total dissipated energy are varied in the computations. A comparison to conventional powder guns is made for a small calibre (bore diameter=20 mm) weapon. Using SESAME equations of state, good efficiency is predicted for hydrogen, helium and polyethylene and medium efficiency for lithium vapor. For muzzle velocities around 1500 m/s, ET guns show similar characteristics as chemical guns. Approaching 2500 m/s, the maximum gas pressure in the ET gun is decisively smaller. With a tolerable pressure of 500 MPa, the hydrogen gun can accelerate a mass of 100 g to nearly 2000 m/s in a barrel length of 2.25 m (2300 m/s in 4.25 m).<>