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Quieting the Boom: The Shaped Sonic Boom Demonstrator and the Quest for Quiet Supersonic Flight.

Quieting the Boom: The Shaped Sonic Boom Demonstrator and the Quest for Quiet Supersonic Flight. By Lawrence Benson. Washington, D.C.: National Air and Space Administration, 2013. Photographs. Illustrations. Bibliography. Index. Pp. 388. $24.00 (Printed version) ISBN: 978-1-626-83-004-2

This book is part of NASA's Aeronautics Book Series and covers development and flight testing of its Shaped Sonic Boom Demonstrator (SSBD).

Benson begins by explaining the science behind the cause of the sonic phenomenon known as a sonic boom. He discusses early research, beginning with Austrian physicist-philosopher Ernst Mach, who explained the concept of sonic booms. Mach determined that the speed of sound was affected by the medium through which an object passes. In the case of flight, sound waves travel faster in warmer temperatures. In recognition of his work, the Mach number (the ratio between the speed of an object and the speed of sound) is named in his honor.

After briefly outlining the events surrounding Yeager's breaking the sound barrier in October 1947, Benson explains how sonic booms are created. He uses multiple diagrams to show both the sonic boom signature and shock cone. Having provided the reader with a basic understanding of sonic booms, Benson discusses in detail subsequent research into the phenomenon as well as the rise in sonic boom complaints submitted to the Air Force, more than 38,000 from 1956 to 1968.

Benson tackles the efforts of the newly formed NASA and its work with the supersonic transport (SST) concept. Coupled with NASA and USAF sonic-boom research of the late fifties and sixties, the FAA entered the sonic-boom-research arena by participating in tests to understand the effects of sonic booms on people, structures, and animals. As a result of concerns over the noise from SSTs, the FAA banned "commercial or civil aircraft from supersonic flight over the landmass or territorial waters of the United States if measurable overpressure would reach the surface" in 1973. With cancellation of the American SST program, research into sonic-booms and their abatement decreased significantly.

The final three chapters focus on the SSBD. Begun in the spring of 2001, the program used a specially modified F-5E fighter to show the persistence of a shaped sonic boom. To achieve the desired results, Northrop engineers produced sixty different aircraft configurations, primarily focused on the F-5E's nose. Ultimately, the final design adding a curved lower addition to the nose that resulted in the moniker "Pelican." In test flights, the Pelican nose proved to be successful in reducing the intensity of sonic booms by creating a plateau of "flattopped" sonic wave signature. Success!

The book ends by describing subsequent, yet dwindling, research efforts. Benson notes that when the day comes for a practical SST, "a worn out former fighter plane, with the front of its fuselage modified to resemble a long pelican's beak, will have helped lead the way."

Quieting the Boom is a very detailed study available in both printed and electronic ( formats. Benson mentions, by name, all of the key participants in an effort to credit everyone involved. Each SSBD test flight is described in detail. The book is heavily annotated, with close to half of the text devoted to endnotes. The graphics are small and challenging for older eyes to read, but the electronic version provides an excellent way to study the graphics in greater enlarged detail. While the technical detail will not appeal to everyone, readers interested in either supersonic flight or flight research will find this work a valuable read.

Lt. Col. Daniel J. Simonsen, USAF (Ret.), Bossier City, Louisiana
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Author:Simonsen, Daniel J.
Publication:Air Power History
Article Type:Book review
Date:Dec 22, 2014
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