RBCC Engine-Airframe Integration on an Osculating Cone Waverider Vehicle
O'Brien, Timothy F.
Lewis, Mark J.
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An analytical vehicle study is performed that integrates a rocket-based combined cycle engine with an osculating cones waverider-based fuselage. The integration of the two concepts brings about an interesting design challenge: predicting the aerodynamic performance of a high-speed fuselage design across the full range of Mach numbers from take-off to orbit that a rocket-based combined-cycle engine will operate. The aerodynamic performance of this class of vehicles is analyzed for on- and off-design Mach numbers and angles of attack. Analytical aerodynamic models are developed for the off-design behavior of both the fuselage of the vehicle and the engine. These models arc combined to predict the powered performance of this class of vehicle along a trajectory. The models developed arc rapid enough that they may be applied to initial design studies, optimization algorithms, or trajectory analyses. The aerodynamic model for the fuselage is based on the tangent-wedge, tangent-cone, and shock-expansion theories for hypersonic flow, and the linearized, small perturbation, velocity potential equations for supersonic and transonic flow. Each model is validated with numerical solutions for an example Mach 12 vehicle design. The results show an accurate prediction of the trends in lift and drag of the vehicle fuselage across a range of Mach numbers between 0.4 and 15. The aerodynamic engine model is based on Prandtl-Meyer flow and the oblique shock relations for the internal compression system, and quasi-one dimensional flow (including finite-rate chemistry) for the combustor flowfield. The strut-based compression model is validated with numerical solutions for a range of Mach numbers between 2.5 and 6. The combustor flowfield model is validated by comparison to two experimental hydrogen-fueled scramjet engines. The results showed that this class of geometry generates very little lift at low speeds (below Mach 3) and will require lift augmentation. The transonic drag rise is modeled analytically and numerically, with maximum inviscid drag coefficient occurring at Mach 1.2. Engine integration has a large effect on off-design behavior, including maximum lift-to-drag ratio and zero lift angle of attack.