NASA-TN-D-7429

Abstract

An experimental study of surface pressure distributions on a family of blunt and sharp large angle cones was made in hypersonic flows of helium, air, and tetrafluoro-methane. The effective isentropic exponents of these flows were 1.67, 1.40, and 1.12. Thus, the effect of large shock density ratios such as might be encountered during planetary entry because of "real-gas" effects could be studied by comparing results in tetra-fluoromethane with those in air and helium. It was found that shock density ratio had a large effect on both shock shape and pressure distribution. The differences in pressure distribution indicate that for atmospheric flight at high speed where "real-gas" effects produce large shock density ratios, large-angle cone vehicles can be expected to experience different trim angles of attack, drag coefficient, and lift-drag ratios than those for ground tests in air wind tunnels. Comparison of the data with several theories indicated that (1) for sharp cones having attached Shockwaves, the sharp-cone solutions provide a good prediction of pressure, and (2) for both sharp and blunt cones having subsonic flow over the forebody, the semiempirical, sin²-deficiency method of Love gave the best prediction of pressure distribution.