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Facing the Heat Barrier: A History of Hypersonics

by T.A. Heppenheimer, NASA History Series, Washington, D.C., 2008, $57.41.

Tom Heppenheimer is well known for his books and articles on technical subjects, and Facing the Heat Barrier is a fitting showcase for his talents. His interesting approach to a difficult topic makes one realize that while hypersonic flight is hardly new, it has always been challenging.

Heppenheimer defines hypersonic flight as flight at airspeeds in excess of Mach 5. And as swift as Mach 5 seems at first, he points out that ballistic missiles and the space shuttle have been operating at far faster speeds for decades now. These hypersonic vehicles are rocket powered, while the future focus of hypersonic flight is fixed on air-breathing scramjet engines.

For many readers, the most interesting chapter may be the one on the magnificent North American X-15, which imposed entirely new demands upon engineers for its structure, aerodynamics, flight controls and instrumentation. Heppenheimer draws on a variety of excellent sources to make a compelling argument for the unique nature of this pioneering aircraft.

After dealing in detail with reentry vehicles and the space shuttle, he presents a comprehensive analysis of why highly touted vehicles such as the National Aerospace Plane (NASP) failed to materialize. He is careful to point out both the possible advantages of the NASP and the reasons for its ultimate cancellation.

Somewhat surprisingly, Heppenheimer concludes on a bit of a down note, stating that there will probably never be a “hypersonic revolution” as there was a “supersonic revolution” because the much-discussed scramjet engine faces insuperable problems in technology and the marketplace. Further, he speculates that piloted space flight may be too costly and dangerous to become routine.

This is not a book for a casual read. But if you’re seriously interested in the subject, it is worth your while, for the author makes it as readable as such a complex topic can be.


Originally published in the July 2009 issue of Aviation History. To subscribe, click here