French-Russian partnership on hypersonic wide-range ramjets

France and Russia have an ongoing fruitful cooperation to jointly develop a wide-range ramjet (WRR) able to accelerate a reusable launch vehicle from similar to Mach 3 to Mach 12. The WRR engine has a fully variable internal geometry, which enables a high performance level over the whole Mach-number range. Propulsion-oriented system studies have been conducted both on 30-t ons-class experimental flight vehicle and on 500 tons-class single-stage-to -orbit (SSTO) reusable vehicles. In particular, the WRR airbreathing propul sion system has been integrated into a SSTO generic vehicle. Then, trajecto ry simulation, using mass, propulsion, and aerodynamic models, has allowed determining the payload as a function of total takeoff weight, confirming t he utility of the variable geometry features of the WRR. Preliminary experi mental and numerical studies have been conducted for several years to desig n the WRR prototype. The present contribution describes the synthesis of th is engine and provides an overview of this common work. Consideration is gi ven to various aspects of the project, including system studies, technology development, and analyses using contour control codes.