8 Jerome C. Hunsaker, "Forty Years of Aeronautical Research," Report of the Smithsonian Institution for 1955 (Washington, 1956), 241-251; Arthur S. Levine, "United States Aeronautical Research Policy, 1915—1958: A Study of the Major Policy Decisions of the National Advisory Committee for Aeronautics,” unpublished Ph. D. dissertation, Columbia University, 1963, 7-16; George W. Gray, Frontiers of Flight: The Story of NACA Research (New York, 1948), 9-15; A. Hunter Dupree, Science in the Federal Government: A History of Policies and Activities to 1940 (Cambridge, Mass., 1957), 283-287; John F. Victory, "The NACA: Cradle of Research," Flying, LX (March 1957), 40-43. In 1921, NACA installed at Langley a pioneering variable-density wind tunnel, which featured the use of compressed air to produce an airflow over small models, thus closely simulating the flow over full-scale aircraft.
9 Hunsaker, "Forty Years of Aeronautical Research," 251-254; Levine, "U.S. Aeronautical Research Policy," 7-41. The passage in 1926 of the Air Commerce Act, which made the Secretary of Commerce responsible for encouraging and regulating civil aviation, clarified the role of NACA and made possible the focus on aeronautical research.
10 The great majority of the people who joined the research staff of NACA during the history of the organization, 1915-1958, held degrees in engineering rather than the physical sciences. Thus "research engineer" became the most common formal designation for those working in aeronautical science for NACA.
11 Gray, Frontiers of Flight, 33-70; Hunsaker, "Forty Years of Aeronautical Research," 254-259. The classic text on subsonic aerodynamics is Richard von Mises, Theory of Flight (2 ed., New York, 1959).
12 Elsbeth E. Freudenthal, The Aviation Business: Kitty Hawk to Wall Street (New York, 1940), 62-304; John B. Rae, "Financial Problems of the American Aircraft Industry," Business History Review, XXXIX (spring 1965), 99-114.
13 By 1938 the altitude record set for aircraft, as established by an Italian aviator, had reached beyond 56,000 feet. Eugene M. Emme, Aeronautics and Astronautics: An American Chronology of Science and Technology in the Exploration of Space, 1915—1960 (Washington, 1961), 162.
14 Hunsaker, "Forty Years of Aeronautical Research," 262.
15 Levine, "U.S. Aeronautical Research Policy," 74-79; Twenty-third Annual Report of the National Advisory Committee for Aeronautics—1937 (Washington, 1938), 2. The NACA organizational structure, in addition to the 15-member Main Committee, which established the research policies of the agency, and the various field installations, eventually included four technical committees, charged with studying problems in particular areas of aeronautical science and recommending to the Main Committee changes in policy and practice. The membership of the various technical committees, like that of the Main Committee, came from the military, the aircraft industry, and the academic community. Each of the technical committees had subcommittees. In 1957 the technical committees were: Aerodynamics, Power Plants, Aircraft Construction, and Operating Problems. See Forty-third Annual Report of NACA—1957 (Washington, 1957).
16 Gray, Frontiers of Flight, 19-33; Hunsaker, "Forty Years of Aeronautical Research," 261-262.
17 Nicholas J. Hoff and Walter G. Vincenti, eds., Aeronautics and Astronautics: Proceedings of the Durand Centennial Conference Held at Stanford University, 5-8 August, 1959 (New York, 1960), 16.
18 Edgar Buckingham, "Jet Propulsion for Airplanes," in NACA Report No. 159, in Ninth Annual Report of NACA —1923 (Washington, 1924), 75-90.
19 Hunsaker, "Forty Years of Aeronautical Research," 266-267; Levine, "U.S. Aeronautical Research Policy," 81-89.
20 See Robert L. Perry, "The Antecedents of the X-1," paper, American Institute of Aeronautics and Astronautics, San Francisco, July 26-28, 1965, 2-17; and Ley, Rockets, Missiles, and Space Travel, 411-413.
21 Hunsaker, "Forty Years of Aeronautical Research," 267. See also John B. Rae, "Science and Engineering in the History of Aviation," Technology and Culture, III (fall 1961), 391-399. Hunsaker, head of the Department of Aeronautical Engineering at the Massachusetts Institute of Technology and a member of the Main Committee since the 1930s, assumed the chairmanship of NACA in 1941 on Bush’s resignation.
22 On the role of air power in the Second World War, see Eugene M. Emme, "The Impact of Air Power Upon History," Air University Quarterly Review, II (winter 1948), 3-13; Eugene M. Emme, ed, The Impact of Air Power: National Security and World Politics (Princeton, N.J., 1959), 209-294; and Wesley F. Craven and Janies L. Cate, eds., History of the Army Air Forces in World War II (7 vols., Chicago, 1948-1955).
