Sizing of scramjet vehicles

Abstract

The current European project LAPCAT II has the ambitious goal to de¦ne a conceptual vehicle capable of achieving the antipodal range Brussels Sydney (∼ 18,000 km) in about 2 h at Mach number Ma = 8. At this high speed, the requirement of high lift to drag (L/D) ratio is critical to high performance, because of high skin friction and wave drag: in fact, as the Mach number increases, the L/D ratio decreases. The design of the vehicle architecture (shape and propulsion system) is, as a consequence, crucial to achieve a reasonably high L/D. In this work, critical parameters for the preliminary sizing of a hypersonic airbreathing airliner have been identi¦ed. In particular, for a given Technology Readiness Level (TRL) and mission requirements, a solution space of possible vehicle architectures at cruise have been obtained. In this work, the Gross Weight at Take-O¨ (TOGW) was deliberately discarded as a constraint, based on previous studies by Czysz and Vanderkerkhove [1]. Typically, limiting from the beginning, the TOGW leads to a vicious spiral where weight and propulsion system requirements keep growing, eventually denying convergence. In designing passenger airliners, in fact, it is the payload that is assumed ¦xed from the start, not the total weight. In order to screen the solutions found, requirements for taking-o¨ (TO) and landing as well as the trajectory have been accounted for. A consistent solution has ¦nally been obtained by imposing typical airliner