Experimental and computational investigation of hypersonic electric-arc airspikes

Drag reduction effects of an electric arc airspike in a hypersonic flow are currently being studied in the Rensselaer Polytechnic Institute 24-inch Hypersonic Shock Tunnel (RPI HST). In tandem these results are being modeled computationally, and compared to existing theory. The arc is driven by a high current lead-acid battery array, producing a maximum of 75-kilowatts into the self-sustaining electrical discharge. The test conditions were for Mach 10, 260 psia stagnation pressure, and 560 K stagnation temperature flow - a low enthalpy, "ideal gas" condition. Schlieren photographs are taken of the arc apparatus and downstream blunt body, with a variety of arc powers and source/body distances. Fast-response accelerometers are used to measure drag on the hanging blunt body. These tests are conducted with and without the arc to establish the most efficient placement and power of the airspike. The computational effort employs the Euler gasdynamic equations to represent a heat source in flow conditions and geometries identical to those tested in the RPI HST. The objective of the combined experimental/computational parametric study is to enhance understanding of the drag reduction features inherent to the airspike phenomenon.