Advanced air-breathing propulsion concepts for winged launch vehicles

Abstract Ascent preformance of five airbreathing propulsion concepts for future reusable two-stage and single-stage launch vehicles designed for horizontal takeoff and landing is evaluated and compared. For direct ascent flights to low Earth orbit an air turborocket propulsion system is superior to an ejector-ramjet design of the single-stage vehicle variant in terms of propellant consumption but is penalized by increased engine weight. A propulsion system consisting of separate rockets and ramjets proves competitive to these systems for a sole accelerating mission. The hydrogen expansion engine system conceived for first stage propulsion of the two-stage space transportation system is preferable to the turboramjet configuration considered. The decision among the engine options, however, depend on specific mission requirements regarding quasistationary and cruise flight legs.