Book Description

Two HTV-1 Hypersonic Test Vehicles, Rounds A-40 and A-41, were flown at Holloman AFB in October 1959, with blunted and sharp 20 degree half angle nose cones, respectively. Round A-40 also incorporated nose cone incidence and a pitch disturber rocket. A maximum flight velociety of 5800 feet per second was attained, corresponding to a local shap cone Mach number and unit Reynolds number of 3.4 and 50 x 10(6) per foot respectively. Fligh dynamics data for the second stage of Round A-40 were obtained from analyses of the vector angle of attack history. The measured maximum trim angle of attack (1.5 degrees) agreed closely with the predicted trim based on an elastic structure and a nose cone incidence of 0.36 degrees. Surface temperatures and aerodynamic heating rates were obtained for one station and three radial positions on the conical portion of the blunted nose cone (Round A-40) and at 3 stations on each of the two longitudinal rays on the sharp cone (Round A-41). In addition, the temperature and heating rates were determined on the cylindrical portion of the Round A-41 payload and on the base of on Stage II fin for both vehicles. The maximum heating rate for the sharp cone was about 30 percent greater for the blunt cone as a result of higher local Mach numbers and Reynolds numbers on the sharp cone. Correlation of the blunted cone circumferential heating rates with the measured angle of attack showed that only a small increase in heating rate (less than about 5 percent increase from the zero angle of attack heating rate) occurs on the windward ray for turbulent heating conditions. The measured decrease in Stanton mumber with increasing Reynolds number (running length) for the sharp cone was found to be in close agreement with turbulent flow theory. Boundary layer transition reversal from turbulent to laminar flow was experienced on both the sharp and blunted tip cones. Transition reversal for the sharp cone, which had almost twice the local Mach number of the blunted cone, was found to occur at an enthalpy ratio, hw/hr, 30 percent greater than for the blunted cone. For both cones turbulent flow occurred within the Mach number and enthalpy region for complete stability of two dimensional disturbance as defined by Dunn and Lin. The possible effects of surface roughness in producing the observed transition reversal are discussed.