Experimental and computational investigation of drag reduction by electric-arc airspikes at Mach 10

Aerodynamic drag reduction effects of an on-axis electric-arc airspike have been investigated in Mach 10 flow using RPI's 24-inch Hypersonic Shock Tunnel (HST). The long-range purpose of this study is to examine the feasibility of airspike-augmented flight for future transatmospheric vehicles. The research objective was to characterize airspike phenomena as a function of input arc power (0 to 50-kW) for a 6-inch diameter blunt-body with a fixed arc-to-forebody separation of 6.38 inches. An array of lead-acid batteries supplied power for the self-sustaining discharge. The joint experimental/ numerical investigation began with the acquisition of a substantial experimental database - against which CFD simulations could be calibrated. The results correlated very well. The HST tests were conducted under low enthalpy, 'ideal gas' conditions with a stagnation pressure of 260-psia and total temperature of 560-K. A fast response PCB accelerometer measured drag forces on the blunt-body model during 1-5 ms of 'unrestrained' motion; the model was loosely suspended by four wires. Luminosity photographs of each test were recorded on 35-mm film and Digital Video (DV) to document the airspike's hypersonic flow structure. The CFD investigation modeled the airspike-equipped blunt body under identical flow conditions, assuming an arc-to-body gap of one vehicle diameter. Results from both experimental data and CFD predictions indicate a 60-70% reduction in drag force compared with the blunt body, power-off case.