A Multiphase Rail Launcher With Circular Geometry and Modular Design: Development, Construction, and First Experiments

Abstract

Electromagnetic railguns allow to accelerate payloads to extremely high muzzle speeds ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 2 km/s). Conventionally, the launcher design is based on two rails. The power supply consists of a capacitor bank and a pulse-forming network allowing unipolar operation. In this work, a different system setup is presented. The idea is to use multiphase alternating current instead of direct current to drive a rail launcher. The basic idea had been brought up in the past in connection with the use of compulsators as power supply. Here, it is suggested to connect the launcher to a (noncompensated) multiphase generator. An interesting but not obvious feature of such an approach is that a stationary acceleration force profile can be realized. However, the launcher becomes more complex as more than two rails are required and an appropriate power supply has to be developed. When considering this approach, an important finding is that if one aims at high speeds, several stages are required. It means that a modular or segmented setup is required. As the passage of the armature between the segments is expected to be a critical point, the idea came up to build a three-phase circular geometry, meaning that the armature leaves at the “muzzle” and re-enters at the “breech” of the launcher. This also allows using an electric motor for a preacceleration in order to minimize sliding contact problems during start. As power supply served a redesigned 100-kW high-current transformer, which can be connected directly to the local power grid. Experimental data including electrical parameters (e.g., an armature current of 20 kA) are presented and discussed. For the first time, it can be experimentally shown that stationary acceleration profiles can be realized, in principle.