The pulse shape requirements of an ETC gun

An assessment of the trade-offs between total electrical energy, the pulse shape which is delivered to the gun and the chemical energy is presented for a future medium/large calibre (circa 130 mm) electrothermal-chemical (ETC) indirect fire gun system. In particular, this paper discusses the implications on total gun system volume i.e. including the electrical power supply and pulse conditioning system. The study considered electrical requirements of up to 25 MJ per shot. The potential performance improvements, compared with a similar sized chemical gun system, are also presented. The FNGUN finite difference based internal ballistics code has been used to simulate the likely trade-offs between electrical input energy, chemical energy and gun performance. This has shown that there is a dependence of the overall system performance on such parameters as: the anticipated electrical behaviour of the plasma; the shape of the electrical pulse supplied to the gun; and the internal ballistics of the gun. In particular it has been found that there is potentially a practical limit to the extent of pulse forming which is worth carrying out before parasitic losses in the pulse conditioning system become too great. Consequently, it is concluded that while some pulse shaping is necessary to meet the requirements of the internal ballistics, i,e, power increasing with time, there is little benefit from further optimisation of the pulse shape.<>