Hypersonics Before the Shuttle A Concise History of the X-15 Research Airplane Dennis R. Jenkins Monographs in Aerospace History Number 18 June 2000 NASA Publication SP-2000-4518 For sale by the U.S. Government Printing Office Superintendento f Documents, Mail Stop: SSOP, Washington, DC 20402-9328 ISBN 0-16 -050363-9 The use of trademarks or names of manufacturers in this monograph is for accurate reporting and does not constitute an official endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and Space Administration. Library of Congress Cataloging-in-Publication Data Jenkins, Dennis R. Hypersonics before the shuttle A concise history of the X-15 research airplane 1 by Dennis R. Jenkins p. cm. -- (Monographs in aerospace history ; no. 18) (NASA history series) (NASA publication ; SP-2000-45 18) Includes index. 1. X-15 (Rocket aircraft)--History. I. Title. II. Series. III. Series: NASA history series W.NASA SP ; 2000-4518. Table of Contents Preface Introduction and Author's Comments ...........................4 Chapter 1 The Genesis of a Research @lane ............................7 Chapter 2 X- 15 Design and Development ...............................2 1 Chapter 3 The Flight Research Program ................................4 5 Chapter 4 The Legacy of the X-15 .................................... 67 Appendix 1 Resolution Adopted by NACA Committee on Aerodynamics ........8 5 Appendix 2 Signing the Memorandum of Understanding ....................8 6 Appendix 3 Preliminary Outline Specification .............................9 2 Appendix 4 Surveying the Dry Lakes ..................................1 02 Appendix 5 R&D Project Card-Project 1226 ............................ 111 Appendix 6 X- 15 Flight Designation System .............................1 15 Appendix 7 Major Michael J . Adams Joins the Program .................... 116 Appendix 8 Astronautwings ......................................... 117 Appendix 9 X-15ProgramFlightLog ..................................1 18 Index ................................................1.2 2 One of the NB-52s flies over the X-15-1 on Edwards Dry Lake in September 1961 . (NASA photo EC6l-0034) Monographs in Aerospace History Number 18 -- Hypersonics Before the Shuttle 3 Introduction and Author's Comments Preface - Preface Introduction and Author's Comments It is a beginning. Over forty-five years have fly 22 more X-15 flights. Tragically, Major Dennis R. Jenkins is elapsed since the X-15 was conceived; 40 Michael J. Adams would be killed on Flight an aerospace engi- since it first flew. And 31 since the program 191, the only fatality of the program. neer who spent ended. Although it is usually heralded as the almost 20 years on most productive flight research program ever Unfortunately due to the absence of a subse- the Space Shuttle pro- undertaken, no serious history has been quent hypersonic mission, aeronautical gram for various con- assembled to capture its design, develop- applications of X-15 technology have been tractors, and has also ment, operations, and lessons. This mono- few. Given the major advances in materials spent time on other graph is the first step towards that history. and computer technology in the 30 years projects such as the since the end of the flight research program, X-33 technology Not that a great deal has not previously been it is unlikely that many of the actual hard- demonstrator. written about the X-15, because it has. But ware lessons are still applicable. That being most of it has been limited to specific aspects said, the lessons learned from hypersonic He is also an author of the program; pilot's stories, experiments, modeling, simulation, and the insight gained who has written over lessons-learned, etc. But with the exception by being able to evaluate actual X-15 flight 20 books on aero- of Robert S. Houston's history published by research against wind tunnel and predicted space history. the Wright Air Development Center in 1958; results, greatly expanded the confidence of and later included in the Air Force History researchers. This allowed the development of Office's Hypersonic Revolution, no one has Space Shuttle to proceed much smoother attempted to tell the entire story. And the than would otherwise have been possible. WADC history is taken entirely from the Air Force perspective, with small mention of the In space, however, the X-15 contributed to other contributors. both Apollo and Space Shuttle. It is interest- ing to note that when the X-15 was con- In 1954 the X-1 series had just broken Mach ceived, there were many that believed its 2.5. The aircraft that would become the X-15 space-oriented aspects should be removed was being designed to attain Mach 6, and to from the program since human space travel fly at the edges of space. It would be accom- was postulated to be many decades in the plished without the use of digital computers, future. Perhaps the major contribution was video teleconferencing, the internet, or email. the final elimination of a spray-on ablator as It would, however, come at a terrible financial a possible thermal protection system for cost--over 30 times the original estimate. Space Shuttle. This would likely have hap- pened in any case as the ceramic tiles and The X-15 would ultimately exceed all of its metal shingles were further developed, but original performance goals. Instead of Mach the operational problems encountered with 6 and 250,000 feet, the program would the (admittedly brief) experience on X- 15A-2 record Mach 6.7 and 354,200 feet. And com- hastened the departure of the ablators. pared against other research (and even oper- ational) aircraft of the era, the X-15 was Many people assisted in the preparation of remarkably safe. Several pilots would get this monograph. First and foremost are Betty banged up; Jack McKay seriously so, Love, Dill Hunley, and Pete Merlin at the although he would return from his injuries to DFRC History Office. Part of this project 4 Hype~SonicSB efore the Shuttle - Monographs in Aerospace History Number 18 Preface Inmoduction and Author's Comments was assembling a detailed flight log (not part and Jack Weber all provided excellent sup- of this monograph), and Betty spent many port for the project. A. J. Lutz and Ray long hours checking my data and researching Wagner at the San Diego Aerospace Museum to fill holes. I am terribly indebted to her. archives, Tony Landis, Brian Lockett, Jay Correspondence continues with several of Miller, and Terry Panopalis also provided the program principals-John V. Becker, tremendous assistance to the project. Scott Crossfield, Pete Knight, and William Dana. Dr. Roger Launius and Steve Garber at Dennis R. Jenkins the NASA History Office, and Dr. Richard Cape Canaveral, Florida Hallion, Fred Johnsen, Diana Cornelisse, February 2000 With the XLR99 engine lagging behind in its development schedule, the X-15 program decided to press ahead with ini- tial flights using two XLRl1 engines-the same basic engine that had powered the Bell X-1 on its first supersonic flight. (San Diego Aerospace Museum Collection) When the Reaction Motars XLR99 engine finally became avail- able, the X-15 began setting records that would stand until the advent of the Space Shuttle. Unlike the XLR11, which was "throttleable" by ignit- ing different numbers of thrust chambers, the XLR99 was a truly throttleable engine that could tailor its output for each specif- ic mission. (San Diego Aerospace Museum Collection) Monographs in Aerospace History Number 18 - Hypersonics Before the Shuttle Hydraulic lifts were installed in the ramp at the Flight Research Center (now the Dryden Flight Research Center) to lift the X-15 up to the wing pylon on the NB-52 mothership. (Jay Miller Collection) 6 Hypersonics Before the Shuttle - Monograph in Aerospace History Number 18 Chapter 1 The Genesis of a Research Airplane Chapter 1 The Genesis of a Research Airplane It was not until the mid-1940s that it became whelming, but there was a growing body of apparent to aerodynamic researchers in the opinion that it should be undertaken. United States that it might be possible to build a flight vehicle capable of hypersonic speeds. The first substantial official support for hyper- Until that time, propulsion systems capable of sonic research came on 24 June 1952 when the generating the thrust required for such vehi- NACA Committee on Aerodynamics passed a cles had simply not been considered techni- resolution to ". .. increase its program dealing cally feasible. The large rocket engines that with the problems of unmanned and manned had been developed in Germany during World flight in the upper stratosphere at altitudes War I1 allowed concept studies to be initiated between 12 and 50 miles," and at Mach num- with some hope of success. bers between 4 and 10." This resolution was ratified by the NACA Executive Committee Nevertheless, in the immediate post-war peri- when it met the following month. A study od, most researchers believed that hypersonic group consisting of Clinton E. Brown (chair- flight was a domain for unmanned missiles. man), William J. O'Sullivan, Jr., and Charles When an English translation of a technical H. Zimmerman was formed on 8 September paper by German scientists Eugen Sager and 1952 at the Langleys Aeronautical Laboratory. Irene Bredt was provided by the U.S. Navy's This group endorsed the feasibility of hyper- Bureau of Aeronautics (BuAer) in 1946, this sonic flight and identified structural heating as preconception began to change. Expanding the single most important technological prob- upon ideas conceived as early as 1928, Sager lem remaining to be solved. and Bredt had concluded during 1944 that a rocket-powered hypersonic aircraft could be An October 1953 meeting of the Air Force's built with only minor advances in technology. Scientific Advisory Board (SAB) Aircraft The concept of manned aircraft flying at Panel provided additional support for hyper- hypersonic speeds was highly stimulating sonic research. Chairman Clarke Millikan to researchers at the National Advisory released a statement declaring that the feasi- Committee for Aeronautics (NACA).' But bility of an advanced manned research aircraft although there were numerous paper studies "should be looked into." The panel member exploring variations of the SZinger and Bredt from Langley, Robert R. Gilruth, played an proposal in the late 1940s, none bore fruit and important role in coordinating a consensus of no hardware construction was undertaken at opinion between the SAB and the NACA. that time. It was from this background, how- ever, that the concept for a hypersonic Contrary to Siinger's conclusions, by 1954 it research airplane would emerge.2 was generally agreed within the NACA and industry that the potential of hypersonic flight At the time, there was no established need for could not be realized without major advances a hypersonic aircraft, and it was assumed by in technology. In particular, the unprecedent- many that no operational military3 or civil ed problems of aerodynamic heating and requirement for hypersonic vehicles would be high-temperature structures appeared to be forthcoming in the foreseeable future. The so formidable that they were viewed as need for hypersonic research was not over- "barriers" to sustained hypersonic flight. Monographs in Aerospace Histoy Number 18 - Hypersonics Before the Shuttle The Genesis of a Research Airplane Chapter 1 Fortunately, the successes enjoyed by the sec- served to test preliminary design configura- ond generation X-1s and other high-speed tions that led to the final hypersonic aircraft research programs had increased political and configuration. Langley also organized a paral- philosophical support for a more advanced lel exploratory program into materials and research aircraft program. The large rocket structures optimized for hypersonic flight. engines being developed by the long-range missile (ICBM) programs were seen as a way Given this, it was not surprising that a team at to provide power for a hypersonic research Langley was largely responsible for defining vehicle. It was now agreed that manned the early requirements for the new research hypersonic flight was feasible. Fortunately, at airplane. The members of the Langley team the time there was less emphasis than now on included Maxim A. Faget in propulsion; establishing operational requirements prior to Thomas A. Toll in configuration, stability, and conducting basic research, and perhaps even control; Norris F. Dow in structures and mate- more fortunately, there were no large manned rials; and James B. Whitten in piloting. All space programs with which to compete for four fell under the direction of Becker. Besides funding. The time was finally right for launch- the almost mandatory elements of stability, ing a hypersonic flight research pr~gram.~ control, and piloting, a fourth objective was outlined that would come to dominate virtual- The specific origins of the hypersonic ly every other aspect of the aircraft's design- research program occurred during a meeting it would be optimized for research into the of the NACA inter-laboratory Research related fields of high-temperature aerodynam- -lane Panel held in Washington, DC, on 4- ics and high-temperature structures. Thus it 5 February 1954. The panel chairman, Hartley would become the first aircraft in which aero- A. SoulC, had directed NACA research air- thermo-structural considerations constituted craft activities in the cooperative USAF- the primary research problem, as well as the NACA program since 1946 and was well primary research objective. versed in the politics and personalities involved. The panel concluded that a wholly The preliminary specifications for the new manned research vehicle was needed, research aircraft were surprisingly brief: only and recommended that NACA Headquarters four pages of requirements, plus six addition- request detailed goals and requirements for al pages of supporting data. A new sense of such a vehicle from the research laboratories. urgency was present: "As the need for the exploratory data is acute because of the rapid In responding to the NACA Headquarters, all advance of the performance of service air- of the NACA laboratories set up small ad hoc craft, the minimum practical and reliable air- study groups during March 1954. Langley plane is required in order that the develop- had been an island of hypersonic study since ment and construction time be kept to a mini- the end of the war and chose to deal with the mum."8 In other versions of the requirements problem in more depth than the other labora- this was made even more specific: "It shall be tories. After the new 11 - inch hypersonic wind possible to design and construct the airplane tunnel at Langley became operational in 1947, within 3 years."g As John Becker subsequent- ". .. a research group headed by Charles H. ly observed, it was obviously impossible McLellan was formed to conduct limited that the proposed aircraft be in any sense an hypersonic re~earch.T~h is group, which optimum hypersonic configuration." reported to the Chief of the Langley Aero- Physics Division, John V. Becker, provided In developing the general requirements, the verification of newly developed hypersonic team developed a conceptual research aircraft theories while investigating such important that served as a model for the eventual X-15. phenomena as hypersonic shock-boundary- The aircraft they conceived was ". .. not pro- layer interaction. The 11-inch tunnel later posed as a prototype of any of the particular 8 Hypersonics Before the Shuttle - Monograph in Aerospace History Number 18