Reusable Booster Stages: A Potential Concept for Future European Launchers

Abstract

This paper describes the final design status of a p artially reusable space transportation system which has been under study for almost five y ears within the German future launcher technology research program ASTRA. It consists of dual booster stages, which are attached to an advanced expendable core. The design of the r eference liquid fly-back boosters (LFBB) is focused on LOX/LH2 propellant and a future advanced gas-generator cycle rocket motor. The preliminary design study was performed in close cooperation between DLR and the German space industry. A structural dynamic analysis of the complete launcher including Ariane 5 core has been carried out and the mechanical lay-out of the nose section has been refined. The aerodynamic section of the paper is de voted to the investigation of the base flow and its interaction with the LFBB's bodyflap and promising measures for improvement are discussed. The propellant feed and tank pressurizat ion system is preliminarily designed by DLR and flight abort scenarios are investigated che cking engine-out capability. Throttling demand on the reusable engine is relatively benign and its demand on the reusable engines' internal conditions will be described. The semi-reu sable launcher has been subject to a System Requirements Review with an international board in 2004. Major points of the review are summarized. Realizing the fact that a si ngle launch system application alone might not be sufficient to justify the development of a reusable stage, the options for continuous operation of such stages or of their der ivatives in a timeframe of at least 50 years have been investigated. The paper finally assesses a long-term, strategic scenario of the reusable stage’s operation. Some data of the prelim inary sizing and payload performance of these evolved launchers are provided.