ACKNOWLEDGMENTS

Robert S. Houston, a historian at the Air Force Wright Air Development Center, wrote the most frequently quoted X-15 history in 1959. This narrative, unsurprisingly, centered on the early Air Force involvement in the program, and concentrated mostly—as is normal for Air Force histories— on the program management aspects rather than the technology. Dr. Richard P. Hallion, later the chief historian for the U. S. Air Force, updated Houston’s history in 1987 as part of volume II of The Hypersonic Revolution, a collection of papers published by the Aeronautical Systems Office at Wright-Patterson AFB. Hallion added coverage of the last nine years of the program, drawing mainly from his own On the Frontier: Flight Research at Dryden, 1946-1981 (Washington, DC: NASA, 1984) and "Outline of the X-15’s Contributions to Aerospace Technology," written in 1977 by Ronald G. Boston. These historians did an excellent job, but unfortunately their work received comparatively limited distribution.

I began this history by using these earlier works as a basis, checking the sources, expanding upon them as appropriate, and adding a NACA/NASA and Navy perspective. Amazingly, almost all of the original source documentation still existed in one archive or another, allowing an evaluation of the tone and inflection of some of the earliest material. Although it is largely a new work, anybody who is intimately familiar with the earlier histories will recognize some passages—the original historians did a remarkably thorough job.

Many people assisted in the preparation of this work, and all gave generously and freely, well beyond any reasonable expectation an author might have. Foremost were Betty J. Love, Tony Landis at Dryden, and Dr. Roger D. Launius at the National Air and Space Museum. The surviving X-15 pilots—Neil A. Armstrong, A. Scott Crossfield, William H. Dana, Brigadier General Joe H.

Engle (USAF, Retired), Colonel William J. "Pete" Knight (USAF, Retired), and Major General Robert M. White (USAF, Retired)—contributed immensely, and several of them read the manuscript multiple times to ensure that nothing significant was missed or misrepresented. John V. Becker and Charles H. Feltz spent many hours explaining things I probably should have already known, greatly improving the manuscript. Then there are the flight planners—Johnny G. Armstrong,^ Richard E. Day, and Robert G. Hoey. I would have missed many subtleties without the patient tutoring from these engineers, all of whom read and commented on several versions of this manuscript and continued my education well past my two engineering degrees.

There was correspondence with many individuals who had been involved with the program:

William P. Albrecht, Colonel John E. "Jack" Allavie (USAF, Retired), Colonel Clarence E. "Bud" Anderson (USAF, Retired), Bill Arnold (RMD/Thiokol, Retired), Colonel Charles C. Bock, Jr., (USAF, Retired), Jerry Brandt, Richard J. Harer, Gerald M. Truszynski, and Alvin S. White. In addition, Jack Bassick at the David Clark Company, Stephen J. Garber and Colin A. Fries at the NASA History Office, Michael J. Lombardi at the Boeing Company Archives, Air Force Chief Historian Dr. Richard P. Hallion, Dr. James H. Young and Cheryl Gumm at the AFFTC History Office, and John D. "Jack" Weber at the AFMC History Office all provided excellent support. Friends and fellow authors Gerald H. Balzer, Robert E. Bradley, Benjamin F. Guenther, Scott Lowther, Mike Machat, Michael

Moore, Terry Panopalis, and Mick Roth also assisted.

Others who contributed include Lynn Albaugh at Ames, Jack Beilman, Rodney K. Bogue at DFRC, Anita Borger at Ames, John W. Boyd at Ames, Russell Castonguay at the JPL archives, Erik M. Conway at Langley and NASM, Mark L. Evans at the Naval Historical Center, Dr. Michael H. Gorn at the DfRc History Office, Matt Graham at DFRC, Fred W. Haise, Jr., Wesley B. Henry at the Air Force Museum, T. A. Heppenheimer, James B. Hill at the John Fitzgerald Kennedy Library, Dr. J. D. "Dill" Hunley at the DFRC History Office, Kenneth W. Iliff (DFRC, Retired), Bob James (DFRC, Retired),

Jack Kittrell (DFRC, Retired), Christian Ledet, F. Robert van der Linden at the National Air and Space Museum, Marilyn Meade at the University of Wisconsin, Roger E. Moore, Claude S. Morse at the AEDC, Karen Moze at Ames, Doug Nelson at the AFFTC Museum, Anne-Laure Perret at the Federation Aeronautique Internationale (FAI), Colonel Bruce A. Peterson (USMCR, Retired), Charles E. Rogers at the AFFtC, Mary F. Shafer (DFRC, Retired), Bonita S. Smith at GRC, Colonel Donald M. Sorlie (USAF, Retired), and Henry Spencer.

It all would never have seen the light of day had it not been for Tony Springer of the Aeronautics Research Mission Directorate at NASA Headquarters.