Comparison of scramjet and scramjet propulsion for an hypersonic wave rider configuration

Ramjet propulsion is often proposed for airbreathing applications with speeds higher than Mach 3. However, for speeds higher than Mach 5, the performance of a ramjet drops significantly and the scramjet is the preferred option. The shock-induced combustion ramjet, or shcramjet, is also an interesting alternative at higher flight speeds. Its configuration differs significantly from the scramjet with a longer intake to provide for fuel injection and evaporation while maintaining a lower air temperature to prevent ignition of the flammable mixture with a slower pressure recovery. A detonation wave completes the pressure recovery and ensures ignition of the air-fuel mixture upon reaching the combustion chamber. This longer intake, necessary for adequate air and fuel mixing, can be combined with a much shorter combustion section. Overall, when the entire vehicle is considered, the shcramjet may result in improved performance for the same mission over the scramjet-powered vehicle. To complete a preliminary design of scramjet and shcramjet vehicles powered at hypersonic speeds, an on-design computational tool was developed to optimize their configurations and compare various performance parameters as a function of Mach number in the range from 7 to 12. In order to compare common baselines for the scramjet and the shcramjet, a configuration was chosen with a mass limited to 430 kg for validation with other design tools. Eventually the configurations were optimized for a balance between the thrust-drag and lift-weight forces by tailoring the external geometry and configuring the internal components to offer the best performance for both vehicles. Since a mixing submodel with not yet available to interact with the other submodels, the various performance parameters were calculated and presented graphically for constant combustion efficiency values. Ultimately both configurations give approximately the same performance when compared with the same combustion efficiency. The resulting hypersonic shapes are presented with detailed explanations of their on-design configurations as the Mach number is varied from 7 to 12. © 2008 by the Department of National Defence and Université.