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 The Lockheed D-21 (Project Tagboard) was an unmanned or "drone" aircraft designed to carry out high-speed, high-altitude strategic reconnaissance missions over hostile territory. It is a product of the Lockheed "Skunk Works" program that developed the A-12, YF-12, and SR-71 "Blackbird" manned aircraft in the 1960's. The D-21 ramjet-powered reconnaissance drone was powered by a Marquardt RJ-43 Ramjet . Cruising at Mach 3.3 at an altitude of 90,000 feet, the D-21 had a range of over 3400 nautical miles. The D-21 was guided by an inertial navigation system on a pre-programmed flight profile.

Originally, the D-21 was designed to be launched from the back of a modified A-12 (re-designated M-12) carrier aircraft. The first flight of the D-21/M-12 combination took place on December 22, 1964, but the first D-21 release from an M-12 did not occur until March 5, 1966. two more launches were successful, but on July 30, 1966, a D-21 collided with the M-12 after release, destroying both aircraft and resulting in the death of one of the M-12's crew members. No further "piggyback" launches were attempted.

A new launch system was developed using modified B-52H aircraft as carriers. The new D-21 configuration (designated D-21B) had dorsal mounting hooks for carriage under the B-52's wing, and a solid rocket booster for the initial acceleration required to start the ramjet engine. The first launch from a B-52 took place on November 6, 1967, but the D-21 crashed. Several flights followed in 1968 with mixed success.

The first operational launch was on November 9, 1969, but the D-21B was lost. Several successful operational missions were flown over the next two years, but the D-21 program was highly classified and details have not been released. The program was canceled in 1971 and the D-21s were placed in storage.

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Q-12 / D-21  (full-scale mockup)

Development of the D-21 Mach 3+ reconnaissance drone began in October 1962. The drone, then known by the Lockheed designation Q-12, was intended to supplement the CIA's A-12 aircraft for missions which required exceptionally long range and/or were too sensitive for the use of a manned aircraft. By October 1963, the Q-12's design had been finalized. It was to be an air-launched ramjet-powered vehicle using some key technology from the A-12 program like e.g. the titanium construction. The aircraft was to be launched from the back of a modified A-12 at a speed of Mach 3. Also in late 1963, the Q-12 was renamed D-21 and the carrier aircraft became the M-21 (M = "Mother", D = "Daughter") to prevent confusion from the proliferation of "-12" designations in the Blackbird family. The D-21 also received the project name Tagboard. It must be mentioned that Tagboard was a CIA program (although the USAF was of course deeply involved) and therefore the D-21 was - strictly speaking - not a military aircraft.

The D-21 was powered by a single Marquardt RJ43-MA-11 ramjet. Its double-delta wing plan form was similar to that of the A-12's outer wing sections. For launch, the M-21 accelerated to Mach 3+ at high altitude, the D-21's ramjet was ignited and the drone was released to free flight. This was a very risky maneuver, because the clearance between the D-21's wings and the M-21's vertical tails was rather close, and the drone had to fly through the Mach 3 shockwave of the carrier aircraft. The D-21 had a nominal range of about 5550 km (3000 nm), was equipped with an inertial navigation system and the flight control computer could be pre-programmed with a course consisting of several waypoints. The drone's mission equipment was a single Hycon high-resolution photographic camera. At the end of the flight, the hatch with the camera was dropped over a pre-determined over-water area, where it could be retrieved by a mid-air recovery system. If that failed, the hatch was designed to float until recovered by a ship. The D-21 itself was expendable.

Captive flight testing of the M-21/D-21 combination began in December 1964, and continued through 1965. In the first tests, the D-21 had aerodynamic covers over the intake and exhaust, but because the covers could not be dropped at Mach 3 without damaging the M-21 and/or D-21, they were deleted. The greater drag was overcome by using the D-21's ramjet as the third engine of the combination (the D-21's fuel tanks could be topped off from the M-21 before launch). The first actual launch of a D-21 finally occured on 5 March 1966, followed by two others on 27 April and 16 June that year. These were all moderately successful, but the fourth and final M-21/D-21 launch on 30 July ended in desaster. The D-21 hit the M-21's tail after separation, leading to the crash of both aircraft and the death of one of the two M-21 crewmembers. After this accident, the M-21/D-21 program was terminated.

 

D-21 Drone Archive

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. 

 

 

Project Tagboard

In the early 1960s, Lockheed had developed the Mach 3 "A-12" spy plane that the CIA recognized as a possible mother-ship for an advanced reconnaissance drone. A program to launch such a drone from the A-12 took precedence after Power's U-2 was brought down in the Soviet Union. The highly secret drone was given the preliminary designation of "Q-12.".

To limit its weight and cost, the Q-12 was designed to be expendable. Its camera payload and guidance system were constructed in its nose section to be ejected and recovered after a parachute descent.

The Q-12, its name changed to D-21, was carried on the back of the A-12 launch vehicle designated as "M-21." ("M" designated "Mother" and "D" stood for "Daughter." The project now had the codename "Tagboard".

Built with titanium and various radar-absorbing plastic composites, the "D-21A", looked like a stovepipe with a cone in its inlet. Its vertical tailfin and wings running the length of the stovepipe that gave the drone something of the look of a sweptback manta ray. Forty-two feet, 10 inches, 11,000 pounds, and having a wingspan of 19 feet, the D-21 flew up to 1,700 MPH at a ceiling of 95,000 feet and 3,450 mile range.

A "Q-bay," contained the reconnaissance payload and guidance systems in a module (known as a "hatch") that plugged neatly into the bay where it could be ejected at the end of the mission to be snagged out of the air by a C-130 Hercules similar to the method used by the Air Force to recover film canisters from reconnaissance satellites.

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Document provided by Jim Goodall

The M-21 was a two-seat version of the A-12, with a pylon on the fuselage centerline between the tailfins to carry the drone in a nose-up attitude. A periscope allowed the back-seater, or "Launch Control Officer (LCO)", to keep an eye on the D-21. Two M-21s were built, along with an initial batch of seven D-21s for test flights.

The first (non-launch) flight of the M-21 and D-21 combination was on 22 December 1964 to study aerodynamics and other systems issues. The first launch occurred on 5 March 1966. Though deemed successful, it concerned the flight crew that the drone hovered above the back of the M-21 for several seconds.

The second successful launch took place on 27 April 1966, prompting plans to construct 15 more D-21s. A third flight on 16 June 1966 was successful, however a launch attempt on 30 July ended in disaster when the D-21 collided with the M-21 on release, destroying both aircraft. The two crewmen ejected safely and landed at sea, but one drowned when his pressure suit leaked. This accident terminated the D-21 project as far as the A-12 (M-21) was concerned. The Tagboard project became Senior Bowl and continued with a B-52 used as the mother-ship launch vehicle. The D-21 drone was ultimately replaced by the new KH-11 Keyhole reconnaissance satellite.

Thirty-eight D-21s were built, with 21 expended. The other 17 were put in mothballs at the Davis-Montham Air Force Base "boneyard" near Tucson, Arizona. Four of the drones were eventually transferred to the US National Aeronautics & Space Administration (NASA) in the late 1990s. NASA considered using their D-21s to test a hybrid "rocket-based combined cycle (RBCC)" (ramjet) engine, however, this idea was abandoned, with NASA preferring to use a derivative of the agency's X-43A hypersonic test vehicle for the experiments. The remainder ended up in air museums.
 

 

The D-21 Drone Tagboard

 

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D-21

 The existence of the D-21 was unknown outside those closely involved with its operation until 1977, when seventeen D-21s suddenly appeared at Davis Monthan AFB for long-term storage. The 'mini-blackbird' configuration of the D-21 immediately started aviation enthusiasts speculating on their operational use and gradually the full story emerged.

The loss of Gary Powers in his U-2 over central Russia on 1 May 60 sent shock waves through the administration of President Eisenhower and he quickly decided to ban all further manned over-flights of Russia and China. This decision posed something of a dilemma for Lockheed when they first flew the A-12 on 26 Apr 62, as the CIA planned to use the aircraft as a 'follow-on' aircraft for the U-2 on the USSR over-flight programmed. Planned from the outset as an 'over-flight' rather than a 'stand-off' reconnaissance aircraft, the A-12 possessed blistering performance and was capable of sustaining Mach 3 at 90,000ft, easily beyond the capabilities of the SA-2 Guideline missile. However, the ban on manned over-flights of Russia and China was unequivocal, effectively curtailing at a stroke the reason for the planes existence.

Kelly Johnson, who headed the 'Skunk Works' team responsible for the design of the A-12, had already considered the possibility of mounting an unmanned drone on the A-12, then on 10 Oct 62 the CIA finally authorized him to study just such a system. It was quickly decided that a highly modified version of the Marquardt RJ43-MA-11 ramjet engine, previously used to power the Boeing Bomarc IM-99B missile, could achieve the performance envisaged for the drone - then known as the Q-12. The basic design of the chine delta had already proved itself on the A-12, so this layout was quickly adopted for the drone. Marquardt successfully redesigned the RJ43-MA-11 ramjet engine, finally producing virtually a new engine, designated the XRJ43-MA20S-4, which proved capable of sustained performance for 1.5 hours - a previously unheard of level of performance for a ramjet. By Nov 62, although the actual specification required by the CIA had never been clearly determined, Kelly Johnson had figured out they were looking for a drone with a range of 3,000 miles and a payload of 425lbs including a camera capable of providing 6-inch resolution of targets from the operating altitude. Weighing only 17,000lbs and built of titanium and composite materials, the D-21 would have the lowest Radar Cross section (RCS) of any vehicle constructed at the Skunk Works. The D-21 was designed from the start as a 'one-way' system - after following a pre-planned route to the target and taking the photos, the drone would return to a pre-determined position over the sea, shut the ramjet down and eject its hatch, containing the exposed film, before self-destructing. The hatch would then be snatched from the air by a JC-130 as it descended on its parachute - that was the theory anyway. Only 38 D-21's were built and of those only 21 actually flew - 17 off the B-52H, including the 4 operational missions over China.

On 20 Mar 63, the CIA finally gave Lockheed a contract to build the Q-12 and attention then turned towards the A-12 aircraft that would carry and launch the drone. Whilst still in their design stage, two A-12s (60-6940 '134' and 60-6941 '135') were modified to carry the Q-21 and would be known as M-21s, to avoid confusion with standard A-12s. The two aircraft carried the drone on a top-mounted dorsal pylon located on the rear centerline between the engines and the vertical stabilizers. In addition, the 'Q' bay that normally carried the camera payload, was modified into a second cockpit for the D-21 launch control officer. The designation of the drone was also changed and it was changed from the Q-12 to the D (for daughter) 21 (adopting the numerals of the M-21 'mother-ship'). However, by Oct 63 Kelly Johnson was already beginning to have concerns about the difficulties that would be encountered in launching the D-21 from the M-21, involving as it did a 0.9g pushover maneuver at Mach 3, - considering what eventually happened, he was right to voice his concerns.

After the first M-21 / D-21 combination was fitted together successfully on 19 Jun 64 in the Skunk Works, the items were delivered separately to Groom Lake and on 22 Dec 64 Bill Park took the combination airborne for the first time. However, because of problems with some D-21 components, particularly the Minneapolis-Honeywell Kollsman star tracker guidance system, no launches were possible. Finally, on 5 Mar 66, Bill Park and Keith Beswick successfully launched a D-21 from an M-21 and, although the D-21 was lost 120 miles from the launch point over the Pacific, the basic concept had proved successful. However, Kelly Johnson continued to voice his concerns stating "This was the most dangerous maneuver we have ever been involved in, in any aero-plane I have ever worked on". Kelly's concerns were hardly surprising when you consider the D-21 launch sequence. After a final top up from a tanker, the A-12 would separate and start to climb and accelerate, all the time circulating the D-21's fuel back through the M-21's fuel system to ensure it was cooled, as the D-21s skin temperature rose to 600F. The D-21's ramjet was fired up once the M-21 was above 60,000ft, usually five minutes before launch, and once wound up to full power gave the M-21/D-21 combination an additional 1000lbs of thrust, quickly pushing the speed up to Mach 3.5. Then provided the LSO was happy with the indications he was receiving from the D-21, it was time for the pilot to 'bunt' the combination down and part company with the D-21, or shut the ramjet down, to prevent the M-21 from exceeding the maximum design speed for the aircraft.

The second launch went even better with the D-21 flying 1,200 nm, reaching 90,000ft and Mach 3.3 before a hydraulic pump overheated and failed. On 16 Jun 66 the third test launch proved the most successful. The D-21 flew 1,600nm making 8 programmed turns to remain within sight of a tracking ship, but failed to eject the camera package towards the end of the flight. Still Johnson had his concerns about the safety of launching from the M-21 and proposed substituting the B-52H as a launch platform, with the D-21 propelled to its optimum height and speed by a solid rocket booster stage. Then, on 30 Jul 66, disaster struck on the fourth launch in which it was planned that M-21 '135' would launch D-21 '504'. Shortly after launch at Mach 3.3 the D-21 suffered an 'unstart' of its ramjet, rolled to the right and collided with the right wing of the M-21. This caused the M-21 to pitch-up sharply, breaking off the nose section. The two crewmembers, pilot Bill Park and LSO Ray Torick ejected successfully, but although Bill Park survived, Ray Torick suffered injuries in the high-speed ejection and drowned in the Pacific. All this was captured on film by M-21 '134' flying chase at Mach 3.3. Johnson had, as was so often the case, been proved right and insisted that the program be abandoned - from that point on the D-21 would only be launched from a B-52H.

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 redesignated D-21Bs.

 

 

The D-21 Tagboard Project

 

The US pursued another path towards advanced reconnaissance drones in parallel with the Model 154. In the early 1960s, Lockheed had developed the Mach 3 "A-12" spy-plane, which quickly evolved into the famous "SR-71 Blackbird" strategic reconnaissance aircraft. After the destruction of Powers' U-2 over the USSR in 1960, concepts for an A-12 drone were proposed. Kelly Johnson, in charge of Lockheed's secret "Skunk Works" that had built the A-12, thought the A-12 itself would be too big and complicated to make a useful drone, but felt that the design and technology could be leveraged into a smaller aircraft that could perform the same mission. The small drone could be launched by the A-12.

The ideas congealed into a formal study for a high-speed, high-altitude drone in October 1962. The study was financed by a special USAF "black projects" fund. The drone itself was given the preliminary designation of "Q-12", and was a very deep secret.

Kelly Johnson wanted to power the Q-12 with a ramjet engine built by Marquardt for the Boeing BOMARC long-range SAM. Marquardt's plant was close to Lockheed's, helping ensure security, and the two companies had collaborated on several programs in the past. Conversations with Marquardt engineers indicated the BOMARC ramjet could be used, though the engine, ultimately designated the RJ43-MA-11, needed some work, since it wasn't designed to burn for much longer than it took a BOMARC to hit a target a few hundred kilometers away. In fact, the Q-12's engine had to operate for at least an hour and a half, much longer than any ramjet built to that time.

The Q-12 was not designed to be recoverable in order to limit its weight and cost. Instead, it would eject its nose section, containing the camera payload and the expensive guidance system. The nose section would descend by parachute for recovery.

A mockup of the Q-12 was ready by 7 December 1962. Radar tests indicated that it had an extremely low radar cross section. Wind tunnel tests also indicated the design was on the right track. However, the CIA was not enthusiastic about the Q-12, mostly because the agency was overextended at the time with U-2 missions, getting the A-12 up to speed, and covert operations in Southeast Asia. In contrast, the Air Force was interested in the Q-12 as both a reconnaissance platform and a cruise missile, and the CIA finally decided to work with the USAF to develop the new drone. Lockheed was awarded a contract in March 1963 for full-scale development of the Q-12.

The major initial problem confronted by the design engineers was launch of the Q-12 from the A-12 mother ship. The Q-12 was to be carried on the back of the A-12, with an uncomfortably small amount of clearance between the A-12's fins, and the potential for disaster during separation of the drone from the mother ship was obvious.

The design was finalized in October 1963, and the designations were changed. The drone was now known as the "D-21", while the A-12 launch aircraft was known as the "M-21". "M" stood for "Mother" and "D" stood for "Daughter". The project now had the codename "Tagboard".

The production UAV, the "D-21A", looked like a stovepipe with a cone in its inlet, with a tailfin and wings running the length of the stovepipe that gave the drone something of the look of a sweptback manta ray. It was mostly made of titanium, with some elements made from radar-absorbing plastic composites.

The reconnaissance payload and guidance systems were carried in a "Q-bay" about 1.9 meters (six feet) long. These systems were built into a module that plugged neatly into the bay and was known as a "hatch". As per the original design concept, the hatch would be ejected at the end of the mission, and the aircraft would then blow itself up with a self-destruct charge. The hatch would be snagged out of the air by a C-130 Hercules, a technique that had been refined by the Air Force to recover film canisters from reconnaissance satellites.

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 The M-21 was a two-seat version of the A-12, with a pylon on the fuselage centerline between the tailfins to carry the drone in a nose-up attitude. A periscope allowed the back-seater, or "Launch Control Officer (LCO)", to keep an eye on the D-21. Two M-21s were built, along with an initial batch of seven D-21s for test flights.

The first flight of the M-21 and D-21 combination was on 22 December 1964. The D-21 remained attached to the M-21 throughout the flight, since it was simply to study aerodynamics and other systems issues. Refining the scheme until an actual release seemed possible proved troublesome, and the first launch was not until 5 March 1966. The release was successful, though the drone hovered above the back of the M-21 for a few seconds, which seemed to one of the flight crew like "two hours". Kelly Johnson called it "the most dangerous maneuver we have ever been involved in, in any airplane I have ever worked on." The D-21 itself crashed after a flight of a few hundred kilometers.

This was still not too bad for the first flight of such an advanced machine, but the CIA and the Air Force remained unenthusiastic about the program. Kelly Johnson conferred with Air Force officials to see what he could do to tune the project more closely to the service's needs. Among other things, Johnson suggested launching the D-21 from a B-52 bomber and using a solid rocket booster to get the drone up to speed.

A second successful launch took place on 27 April 1966, with the D-21 reaching its operational altitude of 27,400 meters (90,000 feet) and speed of Mach 3.3, though it was lost due to a system failure after a flight of over 2,200 kilometers (2,200 NMI). This was regarded as very satisfactory progress. The successful tests sharpened the interest of the program's government backers, and by the end of the month a contract for 15 more D-21s had been placed.

A third successful flight took place on 16 June 1966, with the D-21 flying through its complete mission, though the hatch wasn't released due to an electronics failure. However, a launch attempt on 30 July ended in disaster. The D-21 collided with the M-21 on release, destroying both aircraft. The two crewmen ejected safely and landed at sea. The pilot, Bill Park, survived, but the LCO, Ray Torick, drowned when his pressure suit leaked.

All the fears about launching the D-21 from an A-12 had been proven justified, and Kelly Johnson immediately cancelled any more launches from the M-21. However, he felt that the B-52 launch scheme was still practical, and the D-21 program remained alive and well.

Adapting the D-21 for launch from a B-52 was not trivial. The drones had to be broken down, modified, and reassembled to allow fitting the attachment points on top to link the drone to the B-52's pylon and the points on the bottom to link the drone to its solid-rocket booster. The modified drone was designated the "D-21B". The booster was no little RATO pack: it was a solid-fuel rocket with a length of 13.5 meters (44 feet 4 inches) and a weight of 6.025 tons (13,290 pounds), making it longer and heavier than the drone itself. The booster had a single small tailfin on the bottom to ensure that it flew straight. The tailfin folded to ensure ground clearance. The booster had a burn time of about a minute and a half, and a thrust of 121.4 kN (12,380 kgp / 27,300 lbf).

Two B-52Hs were modified to launch the D-21Bs. They were given two very large under-wing pylons to carry the drones, replacing the smaller pylons used for the B-52's Hound Dog cruise missiles. Two independent LCO stations were added at the rear of the bomber's flight deck, along with command and telemetry systems; a stellar navigation system to ensure that the drones were launched from well-defined coordinates to reduce flight guidance error; and a temperature control system to keep the drones at a stable temperature before launch.

First attempted launch of a D-21B was on 28 September 1967, but the drone accidentally fell off the B-52's pylon; its booster lit, but the D-21B went straight into the ground. Kelly Johnson called the incident "very embarrassing." Three more launches were performed from November 1967 through January 1968. None were completely successful, so Johnson ordered his team to conduct a thorough review before renewing launch attempts. The next launch was on 30 April 1968, and was also a failure. The Lockheed engineers went back to the drawing board once more, and on 16 June 1968 they were rewarded with a completely successful flight. The D-21B flew a test mission at the specified altitude and course over its full range, and the hatch was recovered successfully, though it didn't have a camera payload.

The troubles were not over yet, however. The next two launches were failures, followed by another successful flight in December. A launch near Hawaii in February 1969 to simulate an actual operational flight was a failure as well, but the next two flights, in May and July, were both successes.

Tagboard now appeared ready for operational flights. The first operational mission, part of a program designated "Senior Bowl", was on 9 November 1969, with a D-21B sent to observe Lop Nor. The Chinese never spotted the stealthy drone, but it disappeared and was not recovered. Once again, the Lockheed engineers went back to the drawing board. Another test flight was conducted on 20 February 1970, and was successful. However, the next operational mission was not until 16 December 1970. The D-21B made it all the way to Lop Nor and back to the recovery point, but though the hatch was dropped as planned, it did not deploy its parachute and was destroyed on impact.

The third operational flight, on 4 March 1971, was even more frustrating. Once again, the D-21B made it all the way to Lop Nor and back again, and properly discarded the hatch. The hatch actually deployed its parachute, but the midair recovery failed, and a destroyer that tried to pick the hatch out of the sea simply ran it down. The hatch sank and was lost.

The fourth, and as it turned out last, flight of the D-21B was on 20 March 1971. It was lost over China on the outbound leg, apparently having been shot down. In July, the D-21B program was cancelled. Although the problem had suffered from more than its fair share of bugs, it appears the main reasons were the same as those that led to the cancellation of the Model 154 Firefly: Nixon's rapprochement with China and operational introduction of the Big Bird reconnaissance satellite.

When Ben Rich, Kelly Johnson's successor at the Skunk Works, visited Russia in the 1990s after the fall of the USSR, a contact gave him a package that contained parts of the D-21 that had disappeared on the first operational flight. It had crashed in Siberia. The Soviets had apparently been puzzled as to what it was, but it appears that they also obtained the wreckage of the D-21 lost on the fourth operational flight. The Tupolev design bureau reverse-engineered the wreck and came up with plans for a Soviet copy, named the "Voron (Raven)", but it was never built.

38 D-21s were built, with 21 expended. The other 17 were put in mothballs at the Davis-Montham Air Force Base "bone-yard" near Tucson, Arizona. Since the base is open to the public, the exotic D-21s were eventually spotted and photographed, leading to wild speculations as to their nature that were inflamed by misinformation generated by the Air Force. For example, they were described as test machines used in development of the A-12 / SR-71.

The full details didn't come out until 1993, when an author named Jay Miller published a book titled LOCKHEED'S SKUNK WORKS: THE FIRST 50 YEARS that gave a reasonably complete account of the D-21 project. The mothballed drones were passed off to the US National Aeronautics & Space Administration (NASA), which took four, and to a number of air museums.

In the late 1990s, NASA considered using their D-21s to test a hybrid "rocket-based combined cycle (RBCC)" engine, which operates as a ramjet or rocket, depending on its flight regime. However, this idea was abandoned, with NASA preferring to use a derivative of the agency's X-43A hypersonic test vehicle for the experiments.

The Seattle Museum of Flight was one of the museums that received a D-21. The museum also had an A-12, and museum volunteers built a pylon to allow mounting a D-21 on its back. The combination is the central exhibit in the main display area and is one of the most spectacular sights available at any air museum.