The D-21 was carried on a pylon, which held it at a nose-up attitude.
The pylon had latches to hold the D-21, a compressed air emergency jettisoning system, and a fuel line to transfer fuel to the D-21 from the M-21's own tank's. Two additional launch aircraft, TVL-21 Articles 134 and 135, were built. Article 134 would be used for captive test flights, while 135 would make the actual launches. As with the other A-12 derivatives, the M-21s were two-seat aircraft. The launch control officer (LCO) sat in the Q-bay.
When the D-21/M-21 reached the launch point, the sequence would begin. The first step would be to blow off the D-21's inlet and exhaust covers.
These would fragment and leave the ramjet ready to start. With the D-21/M-21 at the correct speed and altitude, the LCO would start the ramjet and the other systems of the D-21. This was controlled via a panel — green lights would indicate the status of each system. The LCO could watch the D-21 through a periscope on the instrument panel. The M-21 launch aircraft had a camera mounted in what was called a 'hot pod' to film the separation.
With the D-21's systems activated and running, and the launch aircraft at the correct point, the M-21 would begin a slight pushover, the LCO would push a final button, and the D-21 would come off the pylon.[308]
The first D-21 was completed in the spring of 1964. As with the U-2s and A-12s before them, the D-21s were given Article numbers. The first was Article 501, with seven D-21s planned for completion by the end of the year. The early D-21s were in a natural metal finish with the outer half of the wings in black. This marked the radar- absorbing plastic material.
After four more months of checkouts and static tests, the aircraft was shipped to Groom Lake and reassembled. Lockheed test pilot William Park was selected to make all the captive and launch tests. Everything was judged ready for the first captive flight. A bridge crane on the ceiling of the hangar was waiting to lift the D-21, swing it over, and lower it onto the M-21.
The first D-21/M-21 captive flight was scheduled for December 22, 1964. This was also the date for the SR- 71's first flight at Palmdale. The dual first flights would be a big plus for Lockheed. The SR-71 test flight was planned for 8:00 A.M., with the D-21/M-21 takeoff to follow at 12:00 P.M. This would allow time for Kelly Johnson to supervise the SR-71 flight, then fly out to Groom Lake. Minor problems pushed back the SR-71's flight until about noon, however. At Groom Lake, William Park and the rest of the D-21/M-21 team awaited their chance. Finally, at about 2:00 P.M., a Lockheed Jetstar landed, Johnson ran up the ladder, patted Park on the head, and told him to take off.
As the D-21/M-21 flew above the snow-dusted hills, Park checked out its handling. Despite the added drag and weight of the D-21, and low-power engines in the M-21, Park found the combination's flight characteristics were the same as the A-12. For this first flight, the M-21 had only a partial fuel load. As with the SR-71 earlier in the day, the M-21/D-21 went supersonic. Due to the late takeoff, it was getting toward dark when the D-21/M-21 and its F-104 chase planes landed.[309]
Because the combination represented a whole new design, the speed and altitude envelope had to be explored in small steps. Johnson had hoped to make the first D-21 free flight on his birthday, February 27, but it was not to be. A problem with control surface flutter appeared with the D-21. During one captive flight in April 1965, both the D-21's elevens were ripped off by flutter. This required a redesign, which involved adding balance weights and control surface locks. By May, the flutter problem had been corrected, and the combination had reached Mach 2.6.
It was at this time that the LCOs for the test launches were selected. Ray Torick and Keith Beswick would alternate as launch officer on the missions.
The launches were to be made over the ocean, west of Point Mugu, on the California coast.
Progress was painfully slow during the summer and fall of 1965; the D-21, its launch mode, the complexity of the D-21's systems, the aerodynamic combination of the two aircraft, and the technical problems of operating a high-speed drone all proved difficult. A new test range was needed, as the D-21/M-21 could not accelerate sufficiently within the range being used for the early tests. This was followed by performance problems; the weight and drag of the D-21 cut into the M-21's speed and range. The D-21/M-21 also showed poor transonic acceleration, particularly on hot days, Several attempts were made to fly to Point Mugu for launch practice, but the plane could not make the range. More powerful engines were fitted to the M-21s, along with a new inlet control system, but the problems persisted.
The old uncertainties with the launch profile also reappeared. The instrumentation system's strain gauges could not measure the launch forces, due to the heat of Mach 3-plus flight. Johnson was unwilling to commit to a launch until he was sure the separation maneuver was understood. The program was effectively stalled. The first batch of D-21 drones had been completed, but Lockheed was yet to launch a single free flight, and Johnson was unwilling to recommend building any more D-21s until it had been proven in flight.
A final problem facing the D-21 program was how to separate the intake and exhaust covers. Fragments could enter the ramjet and strike the M-21.
These fears were justified on the first, and only, attempt to separate the covers. The pieces tore up the chines of 503, causing major damage.
It was decided to leave the covers off. Ironically, this also provided the solution to the drag problem. With the covers off, the ramjet could act as a third engine for the M-21 during the acceleration to launch speed. It would be started at Mach 1.24. Just before launch, fuel from the M-21's tanks would be transferred to top off the D-21, replacing that used during the run-up to the launch point.
By late January 1966, more than a year after the first captive flight, everything seemed ready. The launch forces were understood, the ramjet operations and hatch recovery had been proven, and the launch maneuver had been practiced. Although the Minneapolis-Honeywell guidance system was not ready, this would not affect the test flights.[310] As with the other A-12s, Article 135 was painted all black with white markings. The D-21s were also painted all black. (Article 134 would remain in the silver and black finish.)
The first D-21 launch was made on March 5, 1966. William Park was the pilot, while Keith Beswick acted as LCO. On this first mission, D-21 Article 503 had only a partial load of fuel. After takeoff, the combination headed east. Over Texas, the M-21 rendezvoused with a KC-135 tanker, refueled, and started the run to the launch point. This began over the town of Dalhart, Texas, on a direct course toward Point Mugu. The D-21/M-21 accelerated slowly at first as it crossed New Mexico. When the proper speed was reached, the ramjet was started. The combination began to pick up speed.[311]
As the D-21/M-21 neared the launch point, it was flying at a speed of Mach 3.2 and altitude of 72,000 feet. Once the checkout was completed and the tanks of the D-21 were topped off, Park began a slight climb, followed by a pushover into a slight dive, holding 0.9 gs on the M-21's precise g-meter. Once Park was satisfied with the profile, he gave clearance to launch.
Beswick then pressed the release button.[312] Through the periscope, Beswick could see the D-21 rising off the pylon.
There was a small puff of vaporized fuel as it separated. Article 503 held steady as it rose away from the M- 21. Then, it stopped and seemed to hang perhaps twenty feet above the back of the M-21. For two or three seconds, the D-21 flew in formation with the M-21. Beswick said later at the debrief-ing that it seemed to have flown in formation for 'two hours.' The onboard camera had recorded the sight. Finally, it passed out of the view of the periscope. Article 503 flew for 120 nautical miles before it ran out of fuel. [313]
Despite the successful flight, CIA and air force interest remained limited.
This placed a burden on Lockheed, as the D-21 program was strapped for money. Johnson had discussions with air force officials and offered, if necessary, to have Lockheed crews launch the early operational missions. He was also looking at a new launch profile — attaching a rocket booster to the D-21 and launching the assembly from a B-52. Despite the successful launch, he was still concerned about the risks of the M-21 profile.
A second D-21 launch was made on April 27. This time Torick was the LCO. Article 506 flew for 1,200 nautical miles, holding its course within a half nautical mile throughout the flight. The peak speed was Mach 3.3,
