Cryogenic upper stage engine trade-off

Abstract

These analyses have shown great benefit to Expander cycle. Early in the development of ARIANE 5 two different upper stages was foreseen, one burning storable propellants, the second powered by the current ARIANE i to 4 LOX/LH2 engine HM7B. The first stage powered by the AESTUS Engine was developed and, it is currently flight reference engine. However to follow the commercial satellite market characterised by an increase of the payload and to keeps to ARIANE the dual launch characteristic, the use of a modern upper stage with a very efficient engine has been recognised as the best way. The development of a new cryogenic engine is a tough task which needs a great investment of the ESA countries, so trade-off dedicated to engine cycle, thrust pressure chamber has to be done to anchor the program. The main specifications thrust (Fv), ISPv and mixture ratio (Rm) are issued from Launcher performance analysis which indicate as target Fv = 150 KN ; ISPv = 466 s ; Rm = 6. A new important requirement, to cope with the future ARIANE missions like GEO is the reignition, up to 6, capacity and the possibility for a long, up to 6 hr, coast phase. According this set of specifications Gas Generator, Bleed and Expander cycle were investigated considering two level of thrust combustion pressure (40 bar and 60 bar). Copyright © 2000 by the Centre National d'Etudes Spatiales. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. Introduction The analysis of near future commercial launch market shows the necessity for ARIANE 5 to update its performances. To keep the dual launch capacity the GTO performance has to increase from 6000 Kg, the current payload capacity up to 11,5 T. To cope with new missions, and added flexibility it must be foreseen multiple ignitions, up to 6 and long coast phase (up to 6 hrs). The evolutions for ARIANE 5 are step by step as described in ref. (1] and [2]. The need for an up-todate LOX/LH2 engine to power the new cryogenic upper stage has appeared early in the investigations ARIANE system analysis. To anchor the proposition to ESA to develop in short time the VINCI Engine ref. [3] CNES has performed trade-off regarding thermodynamical cycle engine, thrust combustion chamber pressure. The candidate cycles which have been regarded are ; a) Gas generator cycle, the current cycle for European engines from VIKING to VULCAIN via HM7B ref. [4] b) Bleed cycle like LE5A and B ref. [8] c) Expander cycle like RL10 ref. [7] The preliminary set of specification was the following :