LeRC rail accelerators: Test designs and diagnostic techniques

As a part of electromagnetic propulsion research at Lewis Research Center (LeRC), an in-house effort has been initiated to investigate the feasibility of using rail accelerators for various in-space and to-space propulsion applications. A 1 meter, 4×6 mm bore accelerator has been designed with the goal of demonstrating projectile velocities of 15 km/sec using a peak current of 200 kA. A second rail accelerator, 1 meter long with a 12.5×12.5 mm bore, has been designed with clear polycarbonate sidewalls to permit visual observation of the plasma arc. This paper presents a study of available diagnostic techniques and their application to the rail accelerator. Specific topics of discussion include the use of interferometry and spectroscopy to examine the plasma armature as well as the use of optical sensors to measure rail displacement during acceleration.