ASA 124th Meeting New Orleans 1992 October

2pPA2. Overview of current knowledge and activity in sonic boom research.

Domenic J. Maglieri

Eagle Eng., Inc., 2101 Executive Dr., Hampton, VA 23666

This presentation will introduce the session on sonic booms by providing a brief overview of current knowledge and activity relative to their generation, propagation, and effects. A large percentage of the sonic boom flight test database was acquired in the decade of the 1960s in connection with overland flight of the proposed U.S.-SST. Interestingly, on every one of the measurements that included over 20 different vehicles, the sonic boom signature was basically N wave or sawtooth in character. Sonic boom minimization schemes were addressed but were considered, at the time, to be very costly and questionable. Recent renewed interest in high-speed civil transports (HSCT) stimulated another concerted effort to address the overland sonic boom issue. Analytical and experimental studies have been directed toward vehicle designs that will produce minimized sonic boom signatures, which still allows for a viable airplane. A key parameter in shaping the boom signature for reduced response is to increase the rise time. Such modified waveforms have been shown to be ``do-able'' on wind tunnel experiments out to about 50 body lengths. It is generally believed that these modified (non-N-wave) signatures will persist for very large distances (300 body lengths) in a real atmosphere; however, this has yet to be demonstrated. The influence of temperature, pressure, wind gradients, and turbulence on sonic boom N waves propagating down through the atmospheres has already been established. Molecular relaxation of O[sub 2] and N[sub 2] and relative humidity has also been shown to influence boom signatures, especially rise time. The effect of these parameters on modified waveforms are being established. Finally, some unique features relative to sonic booms produced by vehicles flying at very high altitudes at hypersonic speeds are also presented. [Work supported by NASA and USAF.]