Progress on Hypervelocity Railgun Research for Launch to Space

The Universities of Texas, Minnesota, and New Orleans, and Texas Tech University are undertaking research supported by the Air Force Office of Scientific Research on critical issues for a launch to space from a railgun carried on an airborne platform. The University of Texas at Austin is studying techniques to achieve hypervelocity with a goal of 7 km/s: So far, 5.2 km/s has been achieved in a 7-m augmented railgun using a preinjected plasma armature. Texas Tech University is studying distributed power feed concepts that will improve the efficiency of launch for a long railgun: So far, 11 km/s has been achieved with a plasma arc in a five-stage system. The Universities of Minnesota and New Orleans are investigating the aerothermal behavior of a 10-kg projectile for flight from a high-altitude launch into orbit: So far, the results show that an acceptable amount (~ 15 mm) of nosetip ablation will occur. This paper provides an overview of progress in these areas; more details on specific topics are provided in companion papers.