Lockheed D-21
The Lockheed D-21 “TAGBOARD” was a highly advanced, remotely piloted aircraft (RPA) designed to carry out high-speed, high-altitude strategic reconnaissance missions over hostile territory. Developed by the famed Lockheed “Skunk Works” in the 1960s, the D-21 used technology from the A-12/YF-12/SR-71 “Blackbird” family of high-speed manned aircraft. Unlike the turbojet engines in the Blackbird, however, the D-21 was powered by a Marquardt RJ43 ramjet of 12,000 lbs. thrust.
D-21Bs were used on four flights over communist China under the code name Senior Bowl, but none of these missions fully succeeded. The US Air Force (USAF) canceled the programme in 1971 and put the remaining D-21s in storage.
Tupolev Voron
As told by Scott Lowther in the book Origins and Evolution Lockheed SR-71 Blackbird, the end of the TAGBOARD and Senior Bowl programmes were not the end of interest in the D-21. One of the more remarkable examples of a derivative project was the Tupolev ‘Voron’ (Raven’).
The first D-21B flown over China, so far as the operators of the vehicle knew, vanished, but it didn’t. It would seem that the navigation system failed to turn the craft around after photographing the Chinese nuclear site at Lop Nor, and it continued north into Siberia before running out of fuel and crashing. It was recovered by the Soviets and studied. And, in grand Soviet tradition, in March 1971, the decision was made to copy it. This task was given to the Tupolev Design Bureau. The resulting design could be easily mistaken for a standard D-21, so long as one paid no attention to the Cyrillic.
The Voron was visually almost identical to the D-21, but there were a few differences. Most apparent was a change to the chines… on the Voron they did not curve outwards beyond the main leading edge line of the wing. The inlet spike was contoured differently, with a more pronounced concave curve; and the camera package fairing was a little different. Internal differences were more pronounced. The Marquardt ramjet engine was not slavishly copied, but was replaced with a new design, seemingly a modification of the RD-012 from the ‘Burya’ cruise missile.
Not meant to be launched from atop an M-21 -analogue
The Voron was not meant to be launched like the D-21 from atop an M-21 analogue. This is not surprising, as the M-21/D-21 should have been unknown to the Soviets, while the D-21B wreckage on hand showed evidence of both an underslung booster and overhead carriage. The Soviets, therefore, designed a new booster for the Voron (shorter and fatter than the Lockheed design) and carried the drone beneath, initially, a Tupolev Tu-95KD missile carrier. It was expected that the then under-development Tu-160 would eventually carry the Voron. At the time, the Tu-160 was envisioned as a derivative of the Tu-144 SST. The supersonic bomber would have launched the Voron without the need of the rocket booster, but unlike the M-21, the Tu-160 would have dropped the Voron from beneath.
While lessons seemed to have been learned in the areas of materials and high-speed design, the Voron was not built. As with the D-21, it had difficulty competing against spy satellites, and the Soviets cancelled the programme before construction could begin.
Origins and Evolution Lockheed SR-71 Blackbird is published by Mortons Books and is available to order here.
Photo by Unknown via Globalaviation Instagram page
