Simulation of Hypersonic Conditions Over a Blunt Body Using a Hybrid Rocket with Nitrogen Plume Cooling

Reliable, ground-based simulations of high-enthalpy flows are crucial for hypersonic flight vehicle development, as they allow detailed assessment of aerodynamic behavior, heat transfer, and material durability. Yet, current hypersonic test facilities, such as shock tunnels and arc-heated wind tunnels, have notable constraints: they are costly, require significant preparation time, and are not readily available for testing early-stage designs. This restricted access slows down innovation and limits experimentation with novel hypersonic technologies. This paper introduces an alternative approach that employs hybrid rocket propulsion to generate high enthalpy flows, simulating hypersonic flight conditions. The presented method adapts a laboratory-scale green-propellant hybrid rocket into a gas generator, channeling its exhaust directly onto the leading edge of a subscale test article representing the forebody of a hypersonic craft. The resulting system produces a partial continuum flow around the test object, allowing simultaneous simulation of both the enthalpy and dynamic pressure found in stratospheric hypersonic flight—something traditional arc-jet facilities do not offer. During experiments, the motor performance characteristics, surface pressure distributions, and leading-edge temperatures on the test article were measured and logged. Initial results showed unexpectedly high plume temperatures with impinging enthalpy exceeding those typical of Mach 10 flight. By introducing gaseous nitrogen at the nozzle exit plane, the plume's temperature is significantly reduced, enabling the recreation of flow enthalpies consistent with Mach 6 through 9 flight conditions. As an added benefit, the nitrogen injection changed the exhaust plume’s properties, making experiments more like real atmospheric flight. The presented results demonstrate this method to be effective in providing an affordable, practical platform for early hypersonic research and supports design and endurance studies without expensive facilities. Such affordable options are valuable for maturing innovative concepts prior to undertaking expensive, high-fidelity tests.