Railgun assisted Launches of Projectiles with Sub- and Low - Earth - Orbit – Payloads (The European View)

Abstract

A Railgun-concept for the launch of small payloads into low Earth orbits is currently under investigation. The system design of this entirely new launch system foresees the acceleration of slim projectiles to hypersonic speeds by an electromagnetic railgun. The expected high performance concerning efficiency, cost and repetition rates makes this system attractive for space applications. As a first cornerstone in the development of this unconventional and alternative access to space the launch of scientific experiments into suborbital altitudes is planned, enabling to validate all basic features and characteristics. The first project foresees a 32 MJ railgun system able to launch non-propelled projectiles with experiments for high-atmospheric research to an altitude of 115 km. This application will strongly concentrate on actual market needs and will be capable to provide low-cost flights for atmospheric sounding as a first goal. This will be followed by a system to launch single stage rocket propelled projectiles to put in orbit nano-satellites using a 3.4 GJ railgun with a length of 180 m. One of the main issues to be investigated, beside the gun structure, is the extreme thermal conditions the projectile's surfaces are exposed to, namely high temperatures and high thermal loads. These are caused by friction and turbulent flow properties, when the projectile rushes through the dense Earth's atmosphere in less than 30 s. The important questions to be answered for the design of a hypersonic projectile are the determination of the duration, magnitude and location of the maximum temperatures with respect to the projectile's surface and its corresponding internal structure. For the determination of this complicated physical conditions a DLR has developed a set of self developed design/CFD tools. Results of analysis are heir presented and commented. This paper presents the main concepts and the design aspects with special emphasis on flight mechanics, aero-/thermodynamics, materials and propulsion characteristics.