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Within Kelly Johnson’s family of Blackbirds, the smallest and least known wonder was, and continues to be, the D-21. In both forms (the M/D-21 Tagboard program and the Senior Bowl operational USAF program), this unmanned Blackbird has been carefully hidden behind a veil of secrecy for over 40 years. 

With the demise of the M-21 'mother-ship, the name of the D-21 launch program was changed from 'Tagboard' to 'Senior Bowl', although the D-21 was generally referred to as the 'Tag' and the remaining D-21's were modified for their new task and re-designated D-21Bs.

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D-21B

Because the M-21/D-21 launch procedure was known to be risky, an alternative method had already been proposed before the ill-fated test. A slightly modified D-21 was to be launched from an under-wing pylon on a B-52H. Because of the much slower release speed, the Tagboard drone would have to use a large solid-propellant rocket booster to accelerate it to ramjet ignition speed. The modified drone was designated D-21B (there was no -21A version), and all D-21s on order in mid-1966 were completed as D-21Bs. The two remaining original D-21s were also converted to this standard. Two B-52Hs were modified to launch the D-21B, and each of them could carry two drones. The D-21B had improved remote control and telemetry links, which would remain active up to 10 minutes into an operational mission.

 Two B-52H aircraft (61-0021 and 60-0036) underwent extensive modifications to carry and launch the D-21B from pylons under each wing - the pylons were similar to that used for launching the X-15 from the NASA NB-52B. Further modifications included the installation of two launch panels and a variety of high-speed cameras to record the launch. All operational launches took place from the starboard pylon, the port D-21B was carried as a spare in case of a last minute malfunction. The launch sequence called for the B-52H to fly to a pre-determined launch point before dropping the D-21B from the starboard pylon. Once clear of the aircraft, the Lockheed designed 60' solid rocket would ignite, then as the combination passed through Mach 1.5, the D-21B's ramjet would ignite. After a burn of around 90 seconds the combination would reach Mach 3 and 75,000ft - at this point explosive bolts would fire to separate the D-21B which then flew off alone on its programmed sortie. A special USAF unit, the 4200th Support Squadron was formed to operate the B-52H / D-21B combination and after training at Groom Lake took up permanent residence at Beal AFB in late 1969.

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Plaque at Beale AFB	B-52H with two D-21B Drones	B-52H Stratofortress with two D-21B Drones
Manufacture of B-52H Pylon	B-52H Pylon under construction at the Skunk works	Pylon looking aft
Pylon with weights prior to mating to B-52H	Pylon being mated to the D-21B Drone	B-52H prior to pylon mating
D-21 Lockheed Rocket Booster final Assembly	Booster Engine Final Assembly prior to testing	Booster engine ready for testing
D-21B Booster engine lowers into position at Test Site	Positioning engine for tests	Securing D-21B Booster engine to test frame mounts
Test Site Overview	Close-up of Test Site	Testing the D-21B Lockheed Rocket Booster Engine
Close-up of Test	Manufacture of D-21 Drone	D-21 Drone Lineup
Marquardt XRJ43-MA20S-4 Ramjet Engine mounted in the D-21	Lineup showing Serial Numbers	Final Assembly of D-21 Drone
Final Assembly	D-21 Under Construction	Fwd View of the D-21 During Construction
D-21 Under Construction	D-21 without the engine installed	D-21 nearing Final Assembly
D-21B mated to the B-52H Pylon Assembly	D-21B Assembly mounted to the B-52H Stratofortress	B-52 launch camera for the drones
B-52H Modifications for Launch Control Officer	B-52H Navigators Position	Cutaway drawing of the D-21B and D-21 Drones
Cutaway of D-21B and Lockheed Rocket Booster	D-21B ready for flight	Shot of the D-21B from the Tanker
Two mounted D-21B Drones	B-52H tail number 61-00021 with two D21B Drones	D-21B with Rocket Booster fired
D-21B Sequence of events in Flight	Cutaway of Deployed Hatch	D-21 Lineup

 

Test launches of the D-21B ran from September 1967 to July 1969, and used up 12 Tagboard drones. However, the initial attempts were not very successful, and on the very first one the drone actually just fell off the pylon long before the B-52H had reached the launch area. But the last two test flights of the program were fully successful, ending with recovery of the hatch after the drone had covered more than 5370 km (2900 nm), and the B-52H/D-21B system was declared ready for operational missions.

A total of four operational missions were eventually flown (9 Nov 1969, 16 Dec 1970, 4 Mar 1971, 20 Mar 1971), all over-flying the People's Republic of China under the project code name SENIOR BOWL. Only two (the 2nd and 3rd) drones completed their flights, but in both cases the hatch with the reconnaissance camera could not be recovered because of system malfunctions and/or bad handling of the recovery effort. In July 1971, the Tagboard program was cancelled. The reasons included the poor measure of success of the SENIOR BOWL flights, and the service entry of a new generation of photo reconnaissance satellites which could produce equivalent results without the political risks of flights through denied air space.

The B-52H / D-21B combination was used for 4 operational sorties over China to investigate their nuclear test area at Lop Nor, some 2,000 miles inland of the China-Mongolia border. The first D-21 launched on 9 Nov 69 managed to photograph the site, but then due to a guidance malfunction, failed to execute its turn-back to the recovery area and flew straight on, eventually crashing in the former USSR. Many years later, after the end of the Cold War, Ben Rich of Lockheed visited the Russian Federation and was presented with the remains of the D-21 by the KGB. On 16 Dec 70 another D-21 reached Lop Nor, and returned to the recovery area, but after a flight of 2648mns, the hatch damaged the parachute and the camera package disappeared into the sea. On 4 Mar 71 another D-21 performed perfectly, managing to over-fly Lop Nor, before returning to the recovery area after a flight of 2935nms. Once again the parachute was damaged by the hatch and dropped gently into the sea where it floated. Then, as a Navy ship tried to recover the hatch, it managed to run over it and damage it sufficiently for it to sink. Two weeks later on 20 Mar 71 another D-21 was tracked for 1,900 miles into China before it suffered some kind of malfunction and disappeared - the remains are probably still out there somewhere in the middle of the vast expanse of the Gobi desert, just waiting to be discovered. There is no evidence that the Chinese ever tracked any D-21 whilst they were hurtling over their territory.

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 Late in 1971, as President Nixon decided it was time to improve relations with China, the Defense Department ordered Kelly Johnson that not only was the D-21 program cancelled, but all the tooling was to be destroyed. Kelly Johnson was furious at the premature cancellation of the program and believed that allowing the USAF to hold onto the drones for nine months at Beal, where they were probably taken apart and re-assembled numerous times, probably contributed to their poor operational record. Johnson firmly believed that had the Skunk Works been responsible for maintaining the drones, they would have performed as planned. In terms of its performance in the 4 operational sorties over China, the D-21 performed well, and the inability of the supporting units to recover the exposed film can hardly be blamed on the drone, assuming the hatches was ejected in the correct location. Like every Lockheed 'black' project, the D-21 was at the cutting edge of known technology and given time and the correct support, would probably have performed as advertised. But by the early 1970's reconnaissance satellites were already providing high quality close-up photographs of China and in reality had soon completed performed the mission that sadly eluded the D-21. Nevertheless, the D-21s that survive in museums stand witness to the genius of Kelly Johnson and his 'Skunk Works' team and are the direct predecessors of today's strategic reconnaissance UAVs, such as the Global Hawk.

A total of 38 D-21/D-21B drones were built. 21 of these were expended in tests and operational missions, and the remaining 17 vehicles were placed in storage. In 1976/77, the Tagboard drones were moved to open storage at Davis-Monthan AFB. This was the first time that the general public learned about the existence of the vehicles. It was not before the early 1990s that the whole story of Tagboard and SENIOR BOWL was finally released. The D-21B drones in storage had been re-designated as GTD-21B. In standard aircraft designations, a "GT" prefix means "permanently grounded, used for training", but it is not known whether this is also valid for the Tagboard drone's final designation. Since the mid-1990s, the GTD-21Bs have been released to various museums.