Aerothermal and flight mechanic considerations by development of small launchers for low orbit payloads started from lorentz rail accelerator

DLR − Institute for Aerodynamics and Flow Technology Lilienthalplatz 7, Braunschweig 38108, Germany

Abstract

The injection of small payloads in Low Earth Orbit (LEO) by means of propelled launchers starting from a Lorentz Rail Accelerator (LRA) is a concept that may enable the access to space at extremely low cost. A propelled launcher is required since today a LRA is only able to launch a total mass of a few kilograms with a velocity up to 4.4 km/s but LEOpayloads require approximately 10 km/s at higher launch mass. Velocity difference must be assured with another propulsion system. Furthermore and independent of the type of selected propulsion, such solution has serious consequences on launcher design. Reasons are, e.g., the harsh mechanical loads like high acceleration on the LRA ramp, high deceleration due to pressure drag, unsteady phenomena during the transition from the LRA ramp into the free atmosphere and also due to extreme thermal loads in the first 30 s of flight. The study presents a conceptual design of a nominal payload of 3 kg, including dimensions, mass- and velocitybudget estimations. In the focus of the analysis are several concepts for the thermal protection of critical system like the nose cap, the front part of the fuselage which houses a hybrid kick-off engine, flares, and the attitude control engines. Additionally, the potential of plug nozzles in comparison to classical Laval nozzles as well as trajectory calculations are discussed. They underline that an elliptical orbit between 300 and 400 km is possible.