ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

3aPAa1. Detection of direct and indirect sonic booms from space shuttle landings.

Joseph Cates

B. Sturtevant

Graduate Aeronaut. Labs., California Inst. of Technol., Caltech 301-46, Pasadena, CA 91125

Hiroo Kanamori

California Inst. of Technol., Pasadena, CA 91125

J. Mori

U.S. Geological Survey, Pasadena, CA 91106

Two hundred seismic stations covering over 50 000 square kilometers in Southern California were used to analyze the sonic boom patterns from the landing of STS-42 in November 1993 and STS-58 in January 1994 at Edwards Air Force Base (EAFB). The instrument ground motion traces show separate arrivals which can be identified as the primary boom, creeping waves generated at the edge of the primary boom carpet, and multiple indirect sonic booms refracted from high altitude. The measured arrival times are compared with the results of linear ray tracing calculations through reference temperature and wind profiles for EAFB. The ray calculations accurately predict the measured arrival times and wavefront angles for the primary sonic boom and the creeping waves in shadow regions, and accurately predict the wavefront angles for the indirect booms. Ray theory using the reference atmosphere fails to predict indirect boom arrival time, observed multiple booms within the first shadow region, and extensive overlap of the multiply refracted sonic booms. These results suggest that boom exposure under the real atmosphere may be larger than previously expected.