Crickmore, Lockheed SR-71 Blackbird, 35, 36.
Thornborough and Davies, Lockheed Blackbirds, 56, 57; and Bill Sweetman, Aurora: The Pentagon's Secret Hypersonic Spyplane (Osceola, Wis.: Motorbooks, 1993), 9.
Michelle Briggs, 'Classified D-21 Mini-Blackbird On Display at Arizona Museum,' Pacific Flyer, November 1993, A39.
'Top-Secret D-21 Drone Uncloaked,' Museum of Flight News (January/February 1994), 4, 5.
Curtis Peebles, Guardians (Novato, Calif.: Presidio Press, 1987), chapters 7 and 8.
Miller, Lockheed's Skunk Works, 129.
Rich and Janos, Skunk Works, 270. The Soviet counterpart to the D-21 was the 123 DBR. Although it was a high-speed, high-altitude reconnaissance drone, the 123 DBR had a very different mission profile. It was 95.12 feet long, with a top speed of Mach 2.55, a range of 1,620 nautical miles, and an operating altitude of 69,000 to 72,000 feet. Flight time was about 90 minutes. It was launched from a large trailer by its own KR-15 jet engine and two rocket boosters that separated after liftoff. It carried three AFA-54 vertical cameras and one oblique camera in a detachable nose. As with the D-21, at the end of the mission the 123 DBR's nose would separate; it would then be recovered while the rest of the airframe would crash. Liftoff weight of the 123 DBR was over 63,800 pounds. It was built by the Tupolev Design Bureau and operated by the Soviet army.
The 123 DBR first entered service in the late 1960s and was phased out in the late 1970s/early 1980s. As with the D-21, it would remain Black for a decade. It was not until early 1994 that photos of the 123 DBR were released by the Russians.
Peter M. Grosz, 'So, What's New about Stealth?' Air International (September 1986): 147-51. There is very little documentation about the German World War I 'stealth' aircraft. Although this might suggest some type of secrecy, it is more likely that it was not seen as a very practical project.
Alfred Price, The History of U.S. Electronic Warfare, vol. 1 (Privately Printed: Association of Old Crows, 1984), 260, 261.
Gunston, 'Back to Balloons and Gliders?' Air International (May 1986), 228.
Doug Richardson, Stealth (New York: Orion, 1989), 24–33. From time to time, some aircraft showed a reduced RCS by chance. The German Go 229, another flying wing design, was nearly invisible to radar. It was made of wood and had charcoal mixed with the glue to absorb radar signals. The wood construction also hid the radar return from the engines. The British Vulcan bomber was also hard to detect from some angles.
Alfred Price, The History of U.S. Electronic Warfare, vol. 2 (Privately Printed: Association of Old Crows, 1989), 199, 200. There may have been an attempt to reduce the large RCS of the XB-70. The wing and fuselage formed a corner reflector. The second XB-70 had 5 degrees of dihedral added to the wings. Although described as being done for aerodynamic reasons, it would also cause the radar echo to be dispersed by 10 degrees away from the radar. The (unbuilt) third prototype, the YB-70, was to have had the canard sweep changed from 31 degrees to 51 degrees, which would bring the echo of the canards and wings into line. Before this, the canards would have their own echoes. At best, these efforts had only a minimal effect.
