Pressure investigation of the hypersonic 'Directed-Energy Air Spike' inlet at Mach number 10 with arc power up to 70 kW

The use of thermal energy as a means of enhancing flight performance of blunt bodies at hypersonic speeds is investigated. The "DirectedEnergy Air Spike" (DBAS) inlet concept proposes the beamed transmission of concentrated energy forward of a moving vehicle in order to change the bow shock configuration from a detached normal (strong) shock wave to an oblique, parabolicshaped (weak) shock wave. This new approach provides low aerodynamic drag and heating, and also deflects the oncoming air into an annular hypersonic inlet. The compressed inlet air can either be accelerated to produce thrust or decelerated to extract onboard electric power. A 6in. diameter blunt body model was fabricated and pressure transducers are installed at its surface and equipped with 6-in. long slender plasma torch at the stagnation point. This model has been installed in the RPI 24-in. diameter Hypersonic Shock Tunnel and used to test the Directed-Energy Air Spike concept. Pitot pressures have been measured at the maximum diameter annular region of the blunt body. Surface pressure and pitot rake pressure surveys as well as the Schlieren photographs will be presented for Mach number 10 up to 70 kW power at the tip of the spike § Graduate Student, AIAA Student Member. t Associate Professor of Engineer Physics, AIAA Member. J Active Professor Emeritus Engineering, AIAA Fellow. of Aeronautical Copyright © 1998 by L.N. Myrabo and P G. P. Toro. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. INTRODUCTION In an attempt to travel at ever increasing velocities in an efficient manner, Myrabo and Raizer have recently proposed the "DirectedEnergy Air Spike" (DBAS). The DBAS inlet concept enables active control of external aerothermodynamics for an advanced hypersonic transatmospheric vehicle by replacing directed energy for mass, conventionally in the form of a sharp nosed structure. One major advantage of the directedenergy air spike over a solid mass spike is that it has no weight. In addition, the propulsion system design of a transatmospheric vehicle using the DBAS inlet presents two more advantages: 1) employs a detached parabolic bow shock wave to contain a rarefied, "hot air pocket" that substantially reduces the flow Mach number impacting the vehicle forebody; and 2) directs the incident hypersonic air flow toward the periphery of the craft where the annular inlet of the (MHD) magnetohydrodynamic slipstream accelerator is located. The directed-energy air spike in front of a craft may be created by a shock wave propagating from a weak laser-supported detonation (LSD) wave. The pressure at the LSD wave front, being higher than atmospheric pressure, deflects the incident air flow from the axial direction and forces it to flow over the spike to the periphery of the craft (Figure 1). The feasibility of transatmospheric flight is limited by phenomena such as aerodynamic drag and heating, as well as related thermal management problems. Traditional blunt nosed hypersonic vehicles generate a strong detached, normal shock wave in the nose region, which produces a high aerodynamic drag and low aerodynamic heating. On the other hand, a traditional slender body with a sharp leading edge produces a conical, weak attached shock wave (with low drag), but significant heating is created at the tip of this forebody . American Institute of Aeronautics and Astronautics 1 Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.