Experiments on simple railgun with the compacted plasma armature

The authors\´ objective was to elucidate the physical reasons of the velocity limitation in the plasma armature (PA) railgun at the 6 km/s level. To do this, they designed a simple system having no vacuum and no preaccelerator. The 1-2 g mass projectile is launched at the maximum possible constant acceleration-the limit of the projectile strength or the electrothermal explosion of rail surfaces, while making use of the effects of the material strengthening under the great confining pressure and rail current redistribution due to the presence of conducting shields. Such an approach provides the maximum possible energy efficiency of the launcher at its minimum conceivable length (as short as 50-80 cm). This greatly simplifies the design and fabrication but leads inevitably to the idea of the "fixed round"-"one assembly-one shot". The 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 overload of PA with the ablated matter. The use of a compacted PA allowed the authors 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%. The authors believe that the simplest way to further velocity increase, while taking advantage of the compacted PA, is to increase the barrel length along with a corresponding increase of the energy stored.<>