Impact of mission requirements and constraints on conceptual launch vehicle design

The objective of this paper is to analyse the impact of mission requirement s and constraints on both the optimum vehicle design and the effects on fli ght path selection for two types of reusable two-stage-to-orbit launch vehi cles. The first vehicle type considered provides horizontal take-off and la nding capabilities and is intended to be propelled by an airbreathing propu lsion system during stage I flight. The second vehicle type assumes a verti cal launch and is accelerated by a rocket propulsion system during the boos ter stage ascent flight. The analysis employs a design tool for simultaneou s system and mission optimization. It consists of a CAD-based preliminary v ehicle design tool, aerodynamic and aerothermodynamic calculation software, flight simulation programs, and a two-level decomposition optimization alg orithm enabling simultaneous system and flight optimization. The results to be presented show that the cruise flight requirement for an European launc hed mission of the airbreathing vehicle results in a loss of 60 % payload m ass as compared to a mere accelerated ascent for a near equatorial mission into the same target orbit assuming constant takeoff mass. The strong depen dencies of mission requirements on both the optimal vehicle design and the ascent performance are determined for the rocket-powered vehicle type by va rying the inclination and altitude of the target orbit. (C) 1999 Editions s cientifiques et medicales Elsevier SAS. All rights reserved.