Developed in the early sixties, the A-12 supersonic reconnaissance aircraft had to be distinguished by the highest flight characteristics capable of providing an effective solution to the assigned tasks. At the same time, it was immediately clear that this car would have some drawbacks. The aircraft turned out to be very expensive and difficult to operate, and besides, it was not invulnerable to modern air defense systems. It was necessary to find a new way of conducting reconnaissance from the air and create the appropriate means. The unmanned aerial vehicle D-21 was to be the answer to the existing challenges.
The A-12 reconnaissance aircraft was created by Lockheed for the Central Intelligence Agency. The existing U-2 aircraft no longer fully met the requirements, which led to the formation of a new technical task, which implied an increase in the main characteristics. However, the prospects for the A-12 have been a topic of controversy for some time. On May 1, 1960, a CIA U-2 aircraft was shot down over the Soviet Union. This incident led to a ban on flights of manned reconnaissance aircraft over the territory of the USSR. However, the intelligence department needed new information about a potential enemy, which now had to be collected using new means.
An M-21 carrier aircraft with a D-21A drone. CIA photo
In October 1962, employees of Lockheed's secret department called Skunk Works, led by designer Kelly Johnson, proposed a possible solution to the existing problem. On the basis of the existing A-12 aircraft, it was proposed to develop a carrier for an unmanned reconnaissance vehicle. The task of the carrier was to deliver the drone to a given area, where it was necessary to uncouple. Further, the apparatus, equipped with a ramjet engine, had to independently go to the required area and take photographs.
In the course of preliminary studies and theoretical studies, the optimal appearance of the promising complex was established. It was proposed to build a disposable drone and equip it with a drop container in which control systems and photographic equipment were to be located. It was assumed that such an architecture would minimize the cost of production and operation of equipment. In particular, certain savings were provided due to the repeated use of complex and expensive navigation equipment.
D-21A at the manufacturer's workshop. Photo Testpilot.ru
As a further development of the reconnaissance complex based on the A-12 aircraft, the promising project received the symbol Q-12. This was the designation for the layout presented at the end of 1962 by the developer to a potential customer in the person of the CIA. As far as we know, the leadership of the intelligence organization reacted to the new project without much enthusiasm. With the advent and proliferation of anti-aircraft missile systems, the CIA needed high-altitude high-speed reconnaissance aircraft like the A-12. The Q-12 drone, in turn, was of very limited interest.
Despite the lack of an official order and the mixed reaction of the Central Intelligence Agency, Skink Work specialists continued to work. During this period, they conducted tests of the Q-12 model in a wind tunnel, during which the possibility of obtaining the calculated flight characteristics was fully confirmed. Thanks to this, the work could continue further, but an official order was required from one or another department.
Early work. You can see the structural elements of the carrier and the drone. Photo Testpilot.ru
At the turn of 1962 and 1963, Lockheed offered its new development to the Air Force. This organization became interested in the reconnaissance complex, which, with appropriate modifications, could become the basis for the strike system. Probably, the interest of the Air Force became an additional incentive for the CIA, as a result of which a tripartite contract for the development of a full-fledged project appeared. The document was signed in the early spring of 1963.
The project of a promising unmanned reconnaissance aircraft used in conjunction with a carrier aircraft was named D-21. As part of the design work, the Skunk Works department was supposed to develop a project for the drone itself, as well as create a modernized version of the A-12 aircraft, which was to support the work of the reconnaissance aircraft. The promising D-21 carrier was named M-21. The letters for the names were chosen quite simply. Initially, the concept of a "two-stage" intelligence system was referred to as "Mother and Daughter". Accordingly, the carrier aircraft received the letter "M" from "Mother"), and the drone - "D", i.e. "Daughter" ("daughter"). Subsequently, a new version of the project was developed, which is why the name of the base one was changed to D-21A.
Diagram of the D-21 apparatus with a description of the detachable hardware compartment. Figure Testpilot.ru
The reconnaissance apparatus of the new model had to be distinguished by high flight data, which accordingly affected its design. The overwhelming majority of structural elements were proposed to be made of titanium. At the same time, some parts were made of steel alloys and plastics. Studies have shown that only such a design will allow the D-21 to reach the required speed and withstand the resulting heat loads. As an additional means of reducing the negative effect of heat, a special ferrite-based paint and varnish coating, as well as a fuel skin cooling system, similar to those used on the A-12 and SR-71 aircraft, should be used.
D-21 received a cylindrical fuselage, smoothly mated with a delta wing. The leading edge of the wing had rounded nodules, almost reaching the frontal air intake. The frontal part of the fuselage was made in the form of an air intake with a conical central body. In the tail there was a tapering unit, which housed part of the units of the ramjet engine. The tail unit was provided in the form of a trapezoidal keel. The total length of the vehicle was 13.1 m, the wingspan was 5.8 m. The height was 2.2 m. During the flight on the carrier, the device had to carry the dropping head and tail fairings.
Units of a ramjet engine. Photo Testpilot.ru
The device was equipped with a delta wing with well-developed ogival inflows. The wing was installed with a negative transverse angle V. On the trailing edge of the wing, movable planes were placed that served as elevators and ailerons. Heading control was carried out using the rudder on the trailing edge of the keel.
In the bow of the drone, at a short distance from the air intake, there was a compartment for the instruments. The control equipment and aerial cameras were proposed to be placed in a common container 1, 9 m long, the lower part of which was an element of the fuselage bottom skin. Above the equipment, protective covers were also provided. The instrument compartment was mounted on controlled mounts and could be dropped at a given moment of flight.
The hardware compartment housed an inertial navigation system, an autopilot, a computer for air parameters, as well as a means of maintaining the required climatic conditions. A volume was envisaged for the installation of an aerial camera of existing models corresponding to the task at hand. To save on production of rather complex and expensive control devices, as well as to return films with reconnaissance images, the D-21 project proposed dropping the instrument compartment and rescuing it with a parachute.
A prototype reconnaissance complex is preparing for takeoff. Photo by US Air Force
Even in the course of preliminary studies, it was established that the Marquardt RJ43-MA-11 ramjet engine, previously created for the Boeing CIM-10 Bomarc long-range anti-aircraft missile, should be used as a power plant. After some design changes, such as the finalization of the flame stabilization device, the installation of a new nozzle and the modernization of some other systems, the engine could be used on a reconnaissance vehicle. The main goal of such modifications was to increase the traction duration of the work. The upgraded engine, which received the updated designation XRJ43-MA20S-4, could work without interruption for up to one and a half hours and give a thrust of 680 kgf.
Most of the free volume of the airframe was given for the placement of fuel tanks. A significant volume of the fuselage was allocated under the air intake channel, which provides atmospheric air supply to the engine. As a result, not the largest unmanned vehicle was distinguished by a very dense layout of internal units. During the development of the fuel system, the developments in existing projects were taken into account. In particular, to compensate for the heating of the skin, D-21 received heat exchangers through which the fuel had to circulate. On the bottom of the apparatus, valves were provided for connecting to the fuel system of the carrier aircraft. Through one valve, the tanks were refueled, through the second, fuel was supplied to the casing cooling system.
M-21 and D-21A in flight. Photo by US Air Force
The Lockheed D-21 reconnaissance drone had a take-off weight of 5 tons. The engine used made it possible to reach speeds of up to M = 3, 35 and climb to an altitude of 29 km. The flight range was to exceed 1930 km. Taking into account the use of the carrier aircraft, there was the possibility of a significant increase in the radius of the reconnaissance complex.
A promising unmanned aerial vehicle was to be used with the M-21 carrier aircraft. The carrier was developed on the basis of the existing A-12 supersonic reconnaissance aircraft, which was distinguished by its high characteristics. In fact, the M-21 was the original A-12, devoid of reconnaissance equipment and equipped with some other devices. It was proposed to remove cameras from the compartment located behind the cockpit, instead of which an additional cockpit should be placed there with a workplace for the second crew member who controls the drone. The operator had a set of necessary equipment, and also had a periscope for observing the device during flight and launch.
JC-130B Cat’s-Whiskers aircraft with equipment for "catching" a hardware container. Photo Wvi.com
On the upper surface of the carrier's fuselage, between the keels, it was proposed to mount a pylon with attachments for the D-21. The pylon had valves for connecting fuel systems, as well as mechanical and pneumatic locks with a pusher, which ensured the release of the "daughter" at the command of the operator. According to the results of blowing in the wind tunnel, it was recommended to reduce the height of the pylon, because of which the drone had to be between the keels of the carrier. At the same time, only 15 cm remained between the wing tip of the D-21 and the upper part of the keel of the M-21, which could lead to damage to the equipment. Chief Designer K. Johnson opposed reducing the height of the pylon because of the risks associated with it, but in the final version of the project, just such a solution was used.
As a modification of the existing reconnaissance aircraft, the M-21 carrier had similar flight data. The flight speed reached M = 3.35, the range - up to 2000 km. This was enough for the full exploitation of the new scout.
As conceived by the authors of the project, the carrier plane with the reconnaissance aircraft on the pylon was supposed to take off from one of the airfields and go to the place where the drone was dropped. Having gained the required height and accelerated to a speed of the order of M = 3, 2, the carrier could drop the D-21. After dropping and retracing to a safe distance using remote control, the scout had to independently perform the flight according to the program previously loaded into it. After completing the reconnaissance and taking photographs of the required object, the D-21 was supposed to go to the specified area and descend to an altitude of 18 km. There, a hardware container was dropped, after which a self-liquidator was triggered, destroying the drone. The container with control systems and photographic films fell down and at an altitude of 4.5 km opened the parachute. Further, it should have been picked up with the help of aircraft or ships of the naval forces. In particular, the equipment was provided for "catching" the container right in the air. For this, a special Lockheed JC-130B Cat’s-Whiskers aircraft was built. According to the name of the means of capturing the container, this plane was called "Cat's Whiskers".
The drone while undocking from the carrier. Shot from newsreel
Two M-21 aircraft with serial numbers 60-6940 and 60-6941 were specially built for testing in 1963-64. In addition, Lockheed has assembled seven prototypes of the D-21. All this technique was supposed to be used in tests that started in the spring of 1964. Pilots Bill Park and Art Peterson, who were to manage the "mothers", were involved in the checks, as well as Skunk Works engineers Ray Torik and Keith Beswick, who were responsible for the use of reconnaissance equipment. In the future, responsibilities were distributed as follows. B. Park controlled the carrier, and A. Peterson was responsible for piloting the backup aircraft. R. Torik and K. Beswick alternately performed the duties of the carrier systems operator and the cameraman on the accompanying aircraft.
On April 1, 1964, one of the M-21 aircraft took off for the first time. On June 19 of the same year, ground tests of the M-21 and D-21 bundles began. The first flight of a carrier with a drone on a pylon took place on December 22, on the same day with the first flight of the SR-71A reconnaissance aircraft, created on the basis of the A-12 and intended for the Air Force. The purpose of the first flight was to test the interaction between the carrier and its "payload" when flying at different speeds and altitudes. The unmanned aerial vehicle with the serial number 501 was not dropped during this flight.
Damage received by a reconnaissance vehicle during one of the flights without release. Photo Testpilot.ru
During these tests, the authors of the project faced serious technical and operational problems. The need to correct the identified deficiencies led to a revision of the project schedule. The first discharge of D-21, scheduled for March 1965, had to be postponed for almost a year. Because of this, the first independent flight of the new reconnaissance aircraft took place only on March 5, 66th.
On this day, the prototype of the reconnaissance complex, operated by B. Park and K. Beswick, took off from Vandenberg airbase (California), gained the required altitude and speed, after which the operator reset the unmanned vehicle. During the separation, D-21 # 502 dropped the head and tail fairings, which led to noticeable problems. The fairing shattered into pieces, which struck and damaged the fender flares. Nevertheless, the D-21 was able to move away from the carrier in a regular way and begin an independent flight. According to K. Besvik's recollections, it took just a couple of seconds to separate the apparatus, which, however, seemed like several hours. During the joint flight of the "mother" and "daughter", the drone engine worked, which simplified the exit to the drop point, but led to the use of a significant part of the fuel supply. At a quarter of refueling, the experienced D-21 was able to fly only about 100 miles (approximately 280 km). After that, the device descended, dropped the container with the equipment and self-destructed.
The moment of collision of D-21A # 504 with the carrier aircraft. Photo Wvi.com
On April 27, prototype number 506 was used in tests. Taking into account the experience of the previous test, it was decided to abandon the dropping head fairing. The crew of B. Park and R. Torik successfully completed their task and ensured the flight of an experienced drone. The latter was able to fly about 2070 km. On June 16 of the same year, vehicle # 505, launched by B. Park and K. Beswick, with a full refueling, covered a distance of 2870 km.
The next test flight was planned for July 30, in which it was planned to use the pre-production model # 504. B. Park and R. Torik again lifted the complex into the air and went to the discharge point, which was near the Midway Atoll. An accident occurred during uncoupling. The shock wave emanating from the carrier aircraft "touched" the drone, as a result of which the M-21 lost its keel. At cruising speed, the aircraft had neutral stability, due to which the loss of the tail unit led to a loss of stability and controllability. The plane began to shake, and the resulting overloads led to its destruction. The nose of the fuselage broke away from other units and began to fall.
After the collision, the equipment collapsed. Photo Wvi.com
The aircraft crew managed to eject, soon splashed down and was picked up aboard one of the ships in the area. B. Park escaped with minor injuries, and engineer R. Torik damaged his high-altitude suit during the ejection. Upon falling into the ocean, the suit began to fill with water, which led to the death of the specialist.
The head of the Skunk Works department, K. Johnson, by his own decision, prohibited further flights of M-21 carriers with D-21 reconnaissance aircraft. The opinion about the risks associated with installing the drone at a minimum distance from the keels received the most terrible confirmation. Due to the cancellation of further test flights, the D-21 project was threatened with closure.
The only remaining M-21 aircraft in the aviation museum. Photo Wikimedia Commons
The only remaining aircraft M-12 # 60-6941 due to the termination of tests was sent to the parking lot. Nobody showed interest in this car, which left it in storage for a long time. Later it was transferred to the Seattle Aviation Museum, where it is still located.
The death of a colleague was a serious blow, but the Skunk Works specialists nevertheless found the strength to continue the work. Not wanting to risk it again, the authors of the D-21 project proposed a new version of the reconnaissance complex that could dramatically reduce the danger to the carrier and its crew. Now it was proposed to do without the M-21 supersonic aircraft. Instead, a converted B-52 bomber was supposed to lift the scout into the air. The new version of the project was designated D-21B. The letter "A" was added to the name of the first version, respectively. The work was continued.
