Facing the Heat Barrier - NASA's History Office

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paper studies that investigated the feasibility of flight to orbit using such engines. The next two chapters cover important developments in re-entry that followed the ICBM. Chapter 5, “Widening Prospects for Re-Entry,” shows how work in this area supported the manned space program while failing to offer a rationale for a winged spacecraft, Dyna-Soar. Chapter 6, “Hypersonics and the Shuttle,” begins by outlining developments during the mid-1960s that made it plausible that NASA’s reusable space transporter would be designed as a lifting body and built using hot structures. In fact, the shuttle orbiter came forth as a conventional airplane with delta wings, and was built with aluminum structure covered with thermal-protecting tiles. This discussion indicates how those things happened. Chapter 7, “The Fading, the Comeback,” shows how work with scramjets did not share the priority afforded to the topic of re-entry. Instead it faded, and by the late 1960s only NASA-Langley was still pursuing studies in this area. This ongoing effort nevertheless gave important background to the National Aerospace Plane— but it was not technical success that won approval for NASP. As noted, it was the Strategic Defense Initiative. Within the Strategic Defense Initiative, the scramjet amounted to a rabbit being pulled from a hat, to satisfy Air Force needs. NASP was not well-founded at the outset; it was more of a leap of faith. Chapter 8, “Why NASP Fell Short,” explains what happened. In summary, the estimated performance of its scramjet engine fell well below initial hopes, while the drag was higher than expected. Computational aerodynamics failed to give accurate estimates in critical technical areas. The ejector ramjet, a key element of the propulsion system, proved to lack the desired performance. In the area of materials, metallurgists scored an impressive success with a new type of titanium called Beta-21S. It had only half the density of the superalloys that had been slated for Dyna-Soar, but even greater weight savings would have been needed for NASP. Finally, Chapter 9 discusses “Hypersonics After NASP.” Recent developments include the X-33 and X-34 launch vehicles, which represent continuing attempts to build the next launch vehicle. Scramjets have lately taken flight, not only as NASA’s X-43A but also in Russia and in Australia. In addition, the new topic of Large Eddy Simulation, in computational fluid mechanics, raises the prospect that analysts indeed may learn, at least on paper, just how good a scramjet may be. What, in the end, can we conclude? During the past half-century, the field of hypersonics has seen three major initiatives: missile nose cones, the X-15, and NASP. Of these, only one—the X-15—reflected ongoing progress in aeronautics. The other two stemmed from advances in nuclear weaponry: the hydrogen bomb, which gave rise to the ICBM, and the prospect of an x-ray laser, which lay behind the Strategic Defense Initiative and therefore behind NASP. This suggests that if hypersonics is to flourish anew, it will do so because of developments in the apparently unrelated field of nuclear technology. Introduction 1 F-104: Gunston, Fighters, pp. 120-126. Concorde: Heppenheimer, Turbulent, pp. 202-203, 208. 2 Crickmore, SR-71, pp. 89-91, 95-99, 194. 3 Ritchie, “Evaluation.”Steel: Miller, X-Planes, p. 119. 4 See, for example, Anderson, History, pp. 438-439. 5 Top speed of the V-2 is given as 1,600 meters per second (Dornberger, V-2, p. xix) and as 1,700 meters per second (Naval Research Laboratory, Upper, cited in Ley, Rockets, pp. 596-597); the speed of sound at the pertinent altitudes is 295 meters per second (Kuethe and Chow, Foundations, p. 518). 6 Ley, Rockets, p. 243; Neufeld, Rocket, pp. 85-94. 7 Tsien, “Similarity.” 8 1200ºF: NASA SP-2000-4518, diagram, p. 25. 9 Hallion, Hypersonic. xiii
Abbreviations and Acronyms AAF Army Air Forces AAS American Astronautical Society ACES Air Collection and Enrichment System AEC Atomic Energy Commission AEDC Arnold Engineering Development Center AEV Aerothermodynamic Elastic Vehicle (ASSET) AFB Air Force Base AFSC Air Force Systems Command AGARD Advisory Group for Aeronautical Research and Development AIAA American Institute for Aeronautics and Astronautics AIM Aerothermodynamic Integration Model (HRE) APL Applied Physics Laboratory (Johns Hopkins University) APU auxiliary power unit ARDC Air Research and Development Command (USAF) ARS American Rocket Society ASD Aeronautical Systems Division (USAF) ASSET Aerothermodynamic/elastic Structural Systems Environmental Tests ASV Aerothermodynamic Structural Vehicle (ASSET) BMW Bayerische Motoren-Werke BTU British Thermal Unit CASI Center for Aerospace Information C D coefficient of drag CDE Concept Demonstrator Engine (NASP) CFD computational fluid dynamics CFHT Continuous Flow Hypersonic Tunnel (NACA-Langley) CIA Central Intelligence Agency CIAM Central Institute of Aviation Motors (Moscow) coefficient of lift CL CO2 carbon dioxide DARPA Defense Advanced Research Projects Agency DM Deutschmark DNS Direct Numerical Simulation (CFD) DOD Department of Defense DSB Defense Science Board DTIC Defense Technical Information Center DVL Deutsche Versuchsanstalt für Luftfahrtforschung ELV expendable launch vehicle ºF degrees Fahrenheit FAI Federation Aeronautique Internationale FDL Flight Dynamics Laboratory (USAF) FY Fiscal Year g force of gravity
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