Click on Picture to enlarge

+ Larger Font | - Smaller Font

 

Click on Picture to enlarge

The Lockheed D-21

The Lockheed D-21 is 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.

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.

The D-21B on display (#535) was retired to the Museum in 1993.

SPECIFICATIONS
Span: 19 ft.
Length: 43 ft.
Height: 6 ft.
Weight: 11,200 lbs. without booster
Booster: Lockheed Propulsion Co. solid propellant rocket
Engine: Marquardt RJ-43 ramjet
Armament: None
Crew: None

PERFORMANCE
Maximum speed: Mach 3+
Range: 3,400+ miles
Service Ceiling: above 90,000 ft.

PHOTOS & TEXT COURTESY OF THE AIR FORCE MUSEUM

 

 

Lockheed Skunk Works Classified Project Name: Tagboard

 

Click on Picture to enlarge

Click on Picture to enlarge

The D-21

The Lockheed D-21 unmanned drone was launched at Mach 3 from a pylon mounting on top of the rear fuselage of an A12 Blackbird. The designation of the A12 then became an M21 with the D-21 installed. Two A12's were modified (#60-6940 and #60-6941) to carry the D-21 Drone. In June of 1963 a D-21 was mated to a mother-ship for the first time. Actual first flight did not occur until December of 1964. After flying the Photo Reconnaissance mission, the D-21 flew to friendly territory and the camera was ejected from the D-21 Drone. The cameras were recovered in flight by a C-130 mid-air recovery system. The D-21 drone would self-destruct at a low altitude. Kelly Johnson, Lockheed Skunk Works Chief Engineer, cancelled the M-21 program when a D-21 was launched into the area behind the cockpit of the M-21 resulting in loss of the Launch Control Officer's life and loss of the aircraft. The D-21's then was mated to a B-52H Stratofortress (Project was called Senior Bowl). Five operational missions were flown in this configuration over China. Operations ceased due to political reasons, cost and difficulty of operation. The "Museum of Flight" in Seattle, Washington has the only A-12/Drone display combo in existence.

 

 

Construction

 

Click on Picture to enlarge

D-21 drone Riding Piggyback On An M-21

 Titanium (Beta-120/Ti-13V-11Cr-3A1) Monococque with some composite plastics.

Length: 42 feet, 10 inches

Wingspan: 19 feet, 9 inches

Height: 7 feet, 1/4 inch

Speed: Mach 4 (2,500+mph) at 80,000 to 95,000 feet

Maximum Gross Take-off Weight: 11,000 pounds

Operational Ceiling: 95,000 feet

Maximum Un-refueled Range: 3,000 nautical miles

Armament: None

Power-plant Data: Marquardt RJ43-MA-20 Ramjet with 1,500 pounds thrust

D-21 production: 38 drones

D-21A: M-12 launched, 4 launches

D-21B: B-52H launched, 17 Launches, with 5 operational missions

 

 

D-21 Family Serial Numbers

Notes:   'Launch' is the date the drone was launched. 'From' is the launch platform. 'Notes' include mission length or final disposition. The non-operational missions of 2000+ miles were test missions under operational conditions.

 

Click on Picture to enlarge

D-21 Drone

Model.......Lockheed#......... Launch From.......... Notes

D-21 #501 Modified to D21B Standard. 28 Sept 1967 B-52H accidental drop, no mission flown.

D-21 #502 Modified to D21B Standard. On display at Seattle Museum of Flight Mated to an A-12 Airframe.

D-21 #503 Launched from M21 on 5 March 1966....flew 150 nm. Crew on M21 was Bill Park and Keith Beswick.

D-21 #504 Launched from M21 on 30 July 1966. Drone collided with M21, both destroyed. Lockheed Crew was Bill Park and Ray Torick. Ray was killed but Bill Park survived. This catastrophe ended the M21 Program.

D-21 #505 Launched from M21 on 16 June 1966....flew 1,550 nm. Crew was Park/Beswick.

D-21 #506 Launched from M21 on 27 April 1966....flew 1,120 nm. Crew was Park/Torick.

D-21B #507 Launched from B-52H on 6 Nov 1967.....flew 134 nm.

D-21B #508 Launched from B-52H on 19 Jan 1968....flew 280 nm.

D-21B #509 Launched from B-52H on 2 Dec 1967....flew 1,430 nm

D-21B #510 Disposition Unknown - Not stored at Davis Montham AFB, Arizona.

D-21B #511 Launched from B-52H on 30 April 1968....150 nm.

D-21B #512 Launched from B-52H on 16 June 1968....flew 2,850 nm, no camera carried.

D-21B #513 NASA/stored at Barstow

D-21B #514 Launched from B-52H on 1 July 1968....flew 80 nm.

D-21B #515 Launched from B-52H on 15 Dec 1968....flew 2,953 nm, Camera recovered, photos-fair.

D-21B #516 Launched from B-52H on 28 Aug 1968....flew 78 nm.

D-21B #517 Launched from B-52H on 9 Nov 1969...1st operational mission, camera not recovered.

D-21B #518 Launched from B-52H on 11 Feb 1969....flew 161 nm.

D-21B #519 Launched from B-52H on 10 May 1969....flew 2,972 nm, camera recovered.

D-21B #520 Launched from B-52H on 10 July 1969....flew 2,937 nm, camera recovered; good photos.

D-21B #521 Launched from B-52H on 20 Feb 1970....flew 2,969 nm, camera recovered; good photos.

D-21B #522 Stored at Davis Monthan AFB, AZ  in AMARC as of October 10, 2000

D-21B #523 Launched from B-52H on 16 Dec 1970....flew 2,448 nm, 2nd operational mission, camera not recovered

D-21B #524 Stored at Davis Monthan AFB, AZ  in AMARC. NASA owned.

D-21B #525  NASA owned. On loan to Blackbird Airpark, California

D-21B #526 Launched from B-52H on 4 March 1971....flew 2,935 nm, 3rd operational mission, camera not recovered

D-21B #527 Launched from B-52H on 20 March 1971....flew 2,935 nm, 4th and last operational mission, camera not recovered. D-21 Program closed down.

D-21B #528 -- -- Disposition Unknown

D-21B #529 NASA/stored at Barstow

D-21B #530 On display at Davis Monthan AFB, AZ  in AMARC as of October 10, 2000

D-21B #531 Stored at Davis Monthan AFB, AZ  in AMARC as of October 10, 2000

D-21B #532 Stored at Davis Monthan AFB, AZ  in AMARC as of October 10, 2000

D-21B #533 On display at Pima Air and Space Museum, Tucson, AZ

D-21B #534 Stored at Davis Monthan AFB, AZ  in AMARC as of October 10, 2000

D-21B #535 On display at the USAF Musuem and was retired to the Museum in 1993

D-21B #536 Stored at Davis Monthan AFB, AZ  in AMARC as of October 10, 2000

D-21B #537  NASA/stored at Barstow

D-21B #538 Museum of Aviation in Robbins, GA. As of May 07, 2001 this D-21B is being prepared for display outside the main gate. (Courtesy George Cannon)

Notes:

There are two D-21's on display in the U.S. that have not been identified as to their Serial Numbers. One is located at Beale AFB in California and the other is at Dover AFB Delaware. The following D-21's have unknown disposition: #510 and #528.

 

Click on Picture to enlarge
D-21 Drone	(Photos Courtesy of Lockheed Martin Corporation)	M-21 mated with D-21A Drone

 

 

Project "Senior Bowl"

 

The mating of the D21B Drone to the B-52H bomber was one of the most closely guarded secrets of the Blackbird Program. 

Click on Picture to enlarge
B-52H and D-21B mated together	D-21B  Prior to Launch From B-52H
D-21B Ground View	D-21 Launched with Solid Fuel Booster
Above four Photos Courtesy of Lockheed Martin

 

Project Senior Bowl

 

 

D-21 Ramjet Engine Details

        Editors Note:  Jerry Miller had hands-on experience working with the D-21 Drone. This information is provided to acquaint students of  Aeronautical Study with the inner workings of the D-21 Ramjet Engine and to correct the D-21 Engine Model Number.

I have a special interest in the M/D-21 version and am finding it difficult to correct a continuing, minor error in the Ramjet Engine model number. All current references to this engine identify it as a Marquardt XRJ 43-MA20, the same engine as used on the Bomarc B Interceptor Missile. This is not the case and if possible, I would appreciate your help in spreading this informational fine point. The D-21 engine is properly identified as an XRJ 43-MA20S-4.

 I have intimate knowledge of these engines and of the previous models from which the D-21 engine derived. The XRJ 43-MA20 was a complete, externally mounted, ramjet engine with a fixed geometry, Mach 2.35, isentropic spike inlet. The engines' integral combustion chamber/exit nozzle was designed for relatively low altitude cruise and therefore did not have a high expansion ratio nozzle. The ignition system was two pyrotechnic flares. There was no re-ignition capability. The fuel control and flame holder combustion limits would not allow operation at high altitudes. The MA20 engine, used on the Bomarc, contained an all  pneumatic fuel control that maintained constant Mach Number at two selectable Mach Numbers using pressure signals from the "built in" inlet. This engine could function as an independent external power plant on any vehicle that could reach sufficient speed to cause efficient inlet operation. It was developed in supersonic wind tunnels at Marquardt's Van Nuys, California test facility, flight tested on the Lockheed X-7A3 at Holloman AFB, Alamogordo, NM and deployed operationally on the Bomarc B

The MA20S-4 engine, used in the D-21, used many of the MA20 components, but modified to operate at lower pressures and higher temperatures. The S-4 was immersed in the body of the D-21 and had no inlet structure (because it used the D-21 inlet system). The engine center body and main structure remained, to house the fuel control, fuel pump, fuel injector nozzles and flame holder assembly. The flame holder system was redesigned to allow for stable combustion at extremely high altitude, high temperature and low pressure. Ignition was by TEB (TriEthylBoran) to allow for re-ignition in the event of flameout. The combustion chamber/exit nozzle was redesigned to provide for the much greater expansion ratio required for high altitude cruse. The design also incorporated an ejector system to provide for engine structure cooling.

The pneumatic fuel control computer was modified to function at much lower pressures and higher temperatures. The input pressure signals were modified to accept air data from the D-21 inlet and to maximize full power operation limited only by the D-21 inlet conditions and mission parameters. The fuel flow schedule, pumps, controls and injector nozzles were redesigned to permit accurate flow control and injection at the much lower air flow requirements of extreme high altitude.

If it would be possible to display both of these engines on a dolly, side by side, they would not look at all alike. They have common roots (in the Marquardt 43" diameter ramjet family) but the similarity ends there. So far, attempts to display these engines have been stopped by the environmental concerns of some authorities. Much of the center body construction is a Magnesium Thorium alloy. It may not be possible to overcome this caution, but I would like to see such a display as a means to educate aviation enthusiasts about the success of ramjets, as used in the US.

There are a few photographs (some I have given to the Museum of Flight) and some in Lockheed's archives. Perhaps there were some taken by the Air Force at Beale AFB after I trained them to do engine calibrations for the D-21B.

Best Regards, Jerry Miller
 

The air rushing toward the inlet of an engine flying at high speeds is partially compressed by the so-called ram effect. If the air speed is high enough, this compression can be sufficient to operate an engine without either compressor or turbine. The ramjet has been called a flying stovepipe, because it is open at both ends and has only fuel nozzles in the middle. A straight stovepipe would not work however; a ramjet must have a properly shaped inlet-diffusion section to produce low-velocity, high-pressure air at the combustion section, and it must also have a properly shaped exhaust nozzle. Ramjets can operate at speeds above 320 km/h (about 200 mph), although they become practical for military applications only at very high or supersonic speeds. Because the ramjet depends on the compression of the in-rushing air for its operation, a vehicle powered by a ramjet must first be accelerated by other means to a sufficiently high speed.

Marquardt RJ-43 Ramjet

Click on Picture to enlarge

The Ram Jet takes advantage of the way venture's work in supersonic flight to compress the air entering the engine without the need for a compressor section.

Since the turbine section of an engine is used to drive the compressor, eliminating the compressor also eliminates the need for turbines as well. The result is a very simple and efficient jet engine known as a Ram Jet.

The problem with the Ram Jet is that it will only work in supersonic flight. Therefore, the aircraft would have to have a different engine for subsonic flight. Nevertheless Ram Jets may someday be used on Supersonic or Hypersonic aircraft.

 

Click on Picture to enlarge

USE YOUR BROWSER "BACK" BUTTON TO RETURN TO PERVIOUS PAGE