In-Air-Capturing Development Roadmap (State of the Art)

Abstract

Any RLV degrades the launcher’s performance compared to an ELV due to additional stage inert mass. This mass increase is on the one hand due to increased life-time requirements of the major components. The major impact on additional RLV mass stems from the need to bring the used stages fully intact back to the launch site. This task is a fundamental challenge of all RLV compared to ELV for which expended stages are simply crashing into oceans or desert areas. The controlled deceleration of high-speed vehicles in the atmosphere and the subsequent landing on ground are having a significant impact on the RLV-stage inert mass. Several different technical approaches have been proposed in the past for the return of RLV. The technical approaches of SpaceX and Blue Origin are similar with vertical take-off and vertical landing (VTL) of the reusable stages. Despite the fact that this is obviously a feasible and potentially promising option, several other methodologies of the first stage’s reentry and return exist. Four different return modes are most relevant: RTLS: autonomous rocket-powered return flight (similar to some Falcon 9 missions that return to Cape Canaveral), DRL: down-range landing; in case of Kourou-missions only possible on a sea-going platform (“barge”) which subsequently brings the stage back to the launch site, LFBB: autonomous airbreathing-powered return flight at subsonic speed, IAC: capturing in flight of the winged unpowered stage with an aircraft and subsequent towing back for an autonomous landing in gliding flight. The approach currently chosen by some players in the USA is not necessarily the optimum for each application or different operational scenario. A comparison of the different performances is of strong interest because these are related to stage size and hence cost. Since a reliable and sufficiently precise estimation of RLV costs is almost impossible today, the performance impact comparison gives a first sound indication of how promising the modes are.