Some Aspects Concerning the Design of Multistage Earth Orbit Launchers Using Electromagnetic Acceleration

This paper reports on reflections undertaken to establish a possible multistage space-launch system based on the use of combined electromagnetic and rocket launch technology. It is assumed that the direct access to space is not possible using a single-stage system only, since for such a system, muzzle velocities of approximately 10 km/s are required. Multistage chemical rockets have been successfully used for Low Earth Orbit missions. They are now a mature technology; continued system efficiency improvements are expected to yield only marginal progress. Alternative technology paths, such as the Lorentz rail accelerator (LRA), hold the potential for considerable improvements in first-stage efficiencies compared to rocket systems. Such unconventional solution has serious consequences for the accelerator and payload carrier design. In the first part of this paper, some general aspects (size, forces, energy, and power) of an electromagnetic launcher, which could be able to achieve the required muzzle momentum for such a mission, are discussed. More specifically, the design of such a launcher with respect to the type of electromagnetic LRAs (known also as railguns) and to the armature technology is considered, and also, some of the interstage aspects of such a system are investigated. Special attention is paid to solutions increasing the launch efficiency of the electromagnetic launcher. The second part of this paper considers possible design properties of the rocket carrier (booster and kickoff stage). Propulsion system, structure under high acceleration, thermal protection system (TPS), carrier aerodynamics, and flight mechanic properties are analyzed. The performed analysis confirms that the rocket carrier can be realized with the present technology within the next decade. The conclusion is valid under the assumption that a start velocity from a ground-based electromagnetic LRA is limited to about 4.5 km/s if an adequate TPS is applied. At higher velocities, the extreme heat loads destroy the payload carrier.