Aerothermal and Flight Mechanic Considerations by Development of Small Launchers for Low Orbit Payloads Started from Lorentz Rail Accelerator

Abstract

The injection of small payloads in Low Earth Orbit 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 LEO-payloads require approx. 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 sec of flight. The study presents a conceptual design of a nominal payload of three kilograms, including dimensions, mass- and velocity budget 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 300km and 400km is possible.