EXPERIMENTS ON SIMPLE RAILGUN WITH THE COMPACTED PLASMA ARMATURE

Our objective was to elucidate the physical reasons of the velocity li mitation in the plasma armature (PA) railgun at the 6 km/s level. To d o this, we have designed a simple system having no vacuum and no preac celerator. The 1-2 g mass projectile is launched at the maximum possib le constant acceleration-the limit of the projectile strength or the e lectrothermal explosion of rail surfaces, while making use of the effe cts of the material strengthening under the great confining pressure a nd rail current redistribution due to the presence of conducting shiel ds. Such an approach provides the maximum possible energy efficiency o f the launcher at its minimum conceivable length (as short as 50-80 cm ), This greatly simplifies the design and fabrication but leads inevit ably to the idea of the ''fixed round''-''one assembly-one shot''. Our experiments have confirmed the known hypothesis that the cause of the velocity saturation at the 6 km/s level is drag and decay of PA owing to the increase of the inductive counter-emf with velocity and overlo ad of PA with the ablated matter. The use of a compacted PA allowed us to overcome the ''6 km/s limit'' and to launch a 1 g projectile to 7. 1 km/s in a bore length of 56 cm at a total efficiency of 10%. We beli eve that the simplest way to further velocity increase, while taking a dvantage of the compacted PA, is to increase the barrel length along w ith a corresponding increase of the energy stored.