Investigations on Liquid Fly-Back Boosters Based on Existing Rocket Engines

This paper describes a parametrical investigation of different types of liquid fly-back boosters (LFBB)performed at DLR. The preliminary design and performance estimation is exclusively restricted to the incorporation of rocket motors, already under development or in operation. Staged combustion as well as gas-generator cycle is looked upon. The focus is on the LOX/RP1 RD-170/172 of NPO Energomash/Pratt&Whittney, the NK-33 (AJ-26) of Kuznetzov/Aerojet, the cryogenic RD-0120 of KB Khimavtomatiki, and the LOX/LH2 Vulcain 2 of SNECMA/SEP. The attached reference expendable space transportation system is the Ariane 5 ECB with cryogenic upper stage, but skipped SRB. The basic requirement is to reach almost the same commercial GTO payload as for the launcher with solid rocket boosters. The investigation includes trajectory simulations and optimizations for ascent. Return to the launch site by the LFBB is regarded, concerning the propellant requirements and the loads on the vehicle. The booster geometry is generated by CAD for a preliminary dimensioning and mass estimation. The paper includes a comparison of size and mass, as well as flight data of the different liquid fly-back booster configurations. The relevant rocket engine figures of performance, mass, reusability, and throttling capability are presented