The long, slim aircraft sported two enormous jet engines, a long, sharp, projecting nose, and swept-back wings that appeared far too short to support the fuselage in flight. This revolutionary airplane could fly at three times the speed of sound for more than 3,000 miles without refueling. Toward the end of its flight, when fuel began to run low, it could cruise at over 90,000 feet.

The aircraft had been designed and built for reconnaissance—a projected successor to the U-2. Its development had been carried out in profound secrecy. Despite the numerous designers, engineers, skilled and unskilled workers, administrators, and others who had been involved in the affair, no authentic accounts, and indeed scarcely any accounts at all, had leaked. Many aspects of the plane’s development have not been revealed to this day, and many are likely to remain classified for some time.

The official designation of the aircraft was A-12. It came to be called “Oxcart,” a code word also applied to the program under which it was developed. This remarkable airplane no longer flies, but it left a legacy of technological achievement that points the way to new projects. It became the progenitor of a similar but less sophisticated reconnaissance vehicle called the SR-71, whose existence is well known.

Beyond the U-2

The U-2 dated from 1954, when its development began under the direction of Richard M. Bissell of the CIA. In June 1956, the aircraft became operational, but officials predicted that its useful lifetime flying over the USSR could not be much greater than two years. Its first flight over Soviet territory revealed that the Soviets’ defense warning system not only detected the U-2 but tracked it quite accurately. Nevertheless, it remained a unique and invaluable source of intelligence information for almost four years until Francis Gary Powers was shot down near Sverdlovsk on May 1, 1960.

Even as the U-2 commenced its active career, efforts were under way to make it less vulnerable. The hope was to reduce the vehicle’s radar cross section so it would be more difficult to detect. New developments in radar-absorbing materials achieved considerable success, though not enough to solve the problem. Various far-fetched designs were explored, most of them seeking to create an aircraft capable of flying at extremely high altitudes at relatively slow speeds. None proved practical.

Eventually, in the fall of 1957, Mr. Bissell contracted for an operations analysis to determine how the probability of shooting down an airplane varied with the plane’s speed, altitude, and radar cross section. The analysis demonstrated that supersonic speed greatly reduced the chances of detection by radar. The probability of being shot down was not, of course, reduced to zero, but the supersonic line of approach was eminently worthy of serious consideration.

From then on, attention focused increasingly on the possibility of building a vehicle that could fly at extremely high speeds and altitudes and would also incorporate the best radar-absorbing capabilities. Lockheed and the Convair Division of General Dynamics were informed of the general requirements, and their designers set to work without a contract or government funds. From fall 1957 to late 1958, the designs were continually refined and adapted.

Late in November 1958, a CIA review panel held a crucial meeting and agreed that it appeared feasible to build an aircraft capable of speeds and altitudes that would make it virtually undetectable by radar. The panel recommended asking President Dwight D. Eisenhower to approve—in principle—further development of the project and to make funds available for more studies and tests.

The President and his scientific advisor, Dr. James Killian, were already aware of the research, and the President gave his approval. Lockheed and Convair were then asked to submit definite proposals, and funds were made available. The project took on the code name “Gusto.”

Less than a year later, proposals from the two companies were essentially complete, and in July 1959, the President was again briefed. His final approval allowed the program to proceed.

The Start of Oxcart

The next major step was to choose between the Lockheed and Convair designs. In August 1959, specifications of the two proposals were submitted to a DoD/USAF/CIA selection panel [see box]. The Lockheed design was selected, Project Gusto was terminated, and the program to develop a new U-2 follow-on aircraft was named Oxcart. In September, the CIA authorized Lockheed to proceed with antiradar studies, aerodynamic structural tests, and engineering designs, and in January 1960 gave the green light to produce twelve aircraft.

Pratt & Whitney Division of United Aircraft Corp., which had been involved in project discussions, undertook to develop the A-12’s propulsion system. The J58 engine, to be capable of a speed of Mach 3.0, had been sponsored originally by the US Navy for its own purposes, but Navy interest in its development was diminishing, and the Secretary of Defense had decided to withdraw from the program at the end of 1959. The engine would be further developed and optimized for a speed of Mach 3.2.

The primary camera manufacturer was Perkin-Elmer. Because of the complexity of the design, a backup system might be necessary if the Perkin-Elmer design ran into production problems. Eastman Kodak was also asked to build a camera. Minneapolis-Honeywell Corp. was selected to provide the inertial navigation and automatic flight control systems. The Firewell Corp. and the David Clark Corp. became the prime sources of pilot equipment and associated life-support hardware.

Lockheed’s designer was Clarence L. “Kelly” Johnson, creator of the U-2. He called his new vehicle not A-12 but A-11. Its design exhibited many innovations.

Models of the A-11 were tested and retested, adjusted and readjusted during thousands of hours in the wind tunnel. Mr. Johnson was confident in his design, but no one could say whether the bird would fly, let alone whether it would fulfill the demanding requirements laid down for it. Supersonic airplanes pose many design problems. Their payload-range performance is highly sensitive to engine weight, structural weight, fuel consumption, and aerodynamic efficiency. Small design mistakes can lead to large errors in performance.

New Materials, New Methods

To make the drawings and test the model was one thing; to build the aircraft was another. Most problems arose from the simple fact that when the aircraft flew at its designed speed, its skin could reach temperatures of more than 550° Fahrenheit. No metal hitherto used in aircraft production could withstand such extreme temperatures. Metal that could do so was too heavy.

During the design phase, Lockheed evaluated many materials and finally chose a titanium alloy, a strong, relatively lightweight material resistant to high temperatures. Titanium was scarce and very costly. Methods for milling it and controlling its quality were not fully developed. Some eighty percent of the early deliveries from Titanium Metals Corp. were rejected. Not until 1961, when CIA officials informed Titanium Metal Corp. of the objectives and high priority of the Oxcart program and gained their full cooperation, did the titanium supply become consistently satisfactory.

This solved only an initial problem. One of the virtues of titanium is its exceeding hardness, but this very characteristic makes machining and shaping the material difficult. Drills that worked well on aluminum soon broke. New ones had to be devised. Assembly-line production was impossible; each aircraft of the small Oxcart fleet was, so to speak, turned out by hand.

Since every additional pound of weight was critical, adequate insulation was out of the question. The inside of the aircraft would be like a moderately hot oven. The pilot would have to wear a kind of spacesuit, with its own cooling apparatus, pressure control, oxygen supply, and other necessities. The fuel tanks, constituting by far the greater part of the aircraft, would heat to about 350° F., so that special fuel had to be supplied and the tanks rendered inert with nitrogen.

Lubricating oil was formulated for operation at 600° F. and contained a diluting agent in order to remain fluid at operation below 40° F. Insulation on the plane’s intricate wiring soon became brittle and useless. During the lifetime of the Oxcart, no better insulation was found; the wiring and related connectors required special attention and handling.

The camera window posed its own problems. The Oxcart was to carry a delicate and highly sophisticated camera that would look out through a quartz glass window. There could be no optical distortion, despite the great heat to which the window would be subjected. The equipment needed to be resistant to high temperature, and there could be no temperature fluctuation throughout the window area. It took three years and $2 million to arrive at a satisfactory solution.

The program scored one of its most remarkable successes when the quartz glass was successfully fused to its metal frame by an unprecedented process involving high-frequency sound waves.

Another major problem was to achieve the desired low radar cross section. The airframe areas giving the greatest radar return were the vertical stabilizers, the engine inlet, and the forward side of the engine nacelles. Researchers studied ferrites, high-temperature-absorbing materials, and high-temperature plastic structures to find methods to reduce the return. The vertical tail section fins were constructed from laminated “plastic”—the first such material used for an important part of an aircraft’s structure. With these changes in structural materials, the A-11 was redesignated A-12.

To test the effectiveness of antiradar devices, a small-scale model is inadequate. Only a full-size mockup will do. Lockheed accordingly built one and, as early as November 1959, transported it in a specially designed trailer hundreds of miles from the Burbank plant to the test area. There it was hoisted to the top of a pylon and looked at from various angles by radar. Tests and adjustments went on for a year and a half before the results were deemed satisfactory.

Choosing a Base

One thing to be decided in the earliest stages of the program was where to base and test the aircraft. Lockheed clearly could not do it at Burbank, where the aircraft were being built, if for no other reason than its runway was too short.

The ideal location would be remote from metropolitan areas, well away from civil and military airways, easily accessible by air, blessed with good weather year-round, capable of accommodating large numbers of people, equipped with fuel storage facilities, close to an Air Force installation, and furnished with a runway at least 8,000 feet long. No such place seemed to exist.

Ten Air Force bases programmed for closure were considered, but none provided the necessary security, and annual operating costs at most of them would be unacceptable. Edwards AFB, Calif., seemed a likely candidate, but in the end it was passed over. A secluded site in Nevada was finally chosen. It was deficient in personnel accommodations and fuel storage, and its long-unused runway was inadequate, but security was good or could be made so, and a moderate construction program could provide sufficient facilities.

Construction began in September 1960 and continued on a double-shift schedule until mid-1964. One of the most urgent tasks was to build the runway. According to initial estimates of A-12 requirements, it had to be 8,500 feet long. The existing asphalt runway was 5,000 feet long and incapable of supporting the weight of the A-12. The new runway was built between September 7 and November 15, 1960, and involved pouring more than 25,000 yards of concrete.

Another major problem was to provide some 500,000 gallons of PF-1 aircraft fuel per month. Neither storage facilities nor a means of transporting fuel existed. Trucking in fuel was the most economical solution and could be made feasible by resurfacing no more than eighteen miles of highway leading into the base.

Three surplus Navy hangars were obtained, dismantled, and erected on the north side of the base. More than 100 surplus Navy buildings were brought on base and prepared for occupancy. By early 1962, a tank farm with a capacity of 1,320,000 gallons was ready. Warehousing and shop space were begun and older buildings repaired. The essential facilities were ready for the forecast delivery date of Aircraft No. 1 in August 1961.

The facilities were ready, but the aircraft were not. Delivery was originally promised for the end of May 1961, but the date slipped to August, largely because of Lockheed’s difficulties in procuring and fabricating titanium. Pratt & Whitney had unexpected trouble in bringing the J58 engine up to Oxcart requirements.

In September 1961 Pratt & Whitney informed Lockheed of continuing difficulties with the J58 engine’s weight, delivery, and performance. Completion date for Aircraft No. 1 by now had slipped to December 22, 1961, and first flight to February 27, 1962. Even by this last date the J58 would not be ready, so it was decided that a Pratt & Whitney J75 engine, designed for the F-105 and flown in the U-2, would be used for early flights. The engine, along with other components, could be fitted to the A-12 airframe, and it could power the aircraft safely to altitudes up to 50,000 feet and at speeds up to Mach 1.6.

In January 1962, an agreement was reached with the Federal Aviation Administration that expanded the restricted airspace in the vicinity of the test area. Certain FAA air traffic controllers were cleared for the Oxcart project. Their function was to ensure that aircraft did not violate the order. North American Air Defense Command established procedures to prevent its radar stations from reporting the appearance of high-performance aircraft on their scopes.

A-12 refueling concepts required prepositioning vast quantities of fuel at certain points outside the US. Special tank farms were set up in California; Eielson AFB, Alaska; Thule AB, Greenland; Kadena AB, Okinawa; and Adana, Turkey. Since the A-12 used specially refined fuel, these tank farms were reserved exclusively for the Oxcart program. Small detachments of technicians at these locations maintained the fuel storage facility and arranged for periodic quality-control fuel tests.

First Flight

At the Lockheed Burbank plant, Aircraft No. 1 (serial number 121) received its final tests and checkout in January and February 1962 and was partially disassembled for shipment to the site in a specially designed trailer that cost about $100,000.

Finally, on April 26, 1962, Aircraft 121 was ready. On that day, in accordance with Kelly Johnson’s custom, Louis Schalk took it for an unofficial, unannounced, maiden flight lasting about forty minutes. As in all maiden flights, minor problems were detected, but it took only four more days to prepare the aircraft for its first official flight.

On April 30, 1962, not quite one year later than originally planned, the A-12 officially lifted from the runway. Piloted again by Mr. Schalk, it took off at 170 knots, with a gross weight of 72,000 pounds, and climbed to 30,000 feet. Top speed was 340 knots, and the flight lasted fifty-nine minutes. The pilot reported that the aircraft responded well and was extremely stable. Mr. Johnson declared it the smoothest official first flight of any aircraft he had designed or tested. The aircraft broke the sound barrier on its second official flight, May 4, 1962, reaching Mach 1.1—again with only minor problems.

The new CIA director, John McCone, sent a congratulatory telegram to Kelly Johnson. A critical phase had been triumphantly passed, but there remained the long, difficult, and sometimes discouraging process of working the aircraft up to full operational performance.

Aircraft No. 122 arrived at the base on June 26 and spent three months in radar testing before engine installations and final assembly. Aircraft No. 123 arrived in August and flew in October. Aircraft No. 124, a two-seat version intended for training the project’s pilots, was delivered in November. It was to be powered by the J58 engine, but delivery delays and a desire to begin pilot training prompted a decision to install the smaller J75. The trainer flew initially in January 1963. The fifth aircraft, No. 125, arrived in December.

Engine Problems

At the end of 1962, there were two A-12 aircraft engaged in flight tests. Mach 2.16 and 60,000 feet had been achieved. Progress was still slow, however, because of delays in the delivery of engines and shortcomings in their performance. One of the two test aircraft was still flying with two J75 engines and the other with one J73 and one J38. It had become clear that Pratt & Whitney had been too optimistic in its forecast: Developing the J58 to Oxcart specifications had proved a good deal more difficult than expected.

By the end of January 1963, ten J58s were available, and the first flight with two of them installed occurred on January 13. After that, A-12 aircraft were fitted with their intended propulsion system. Flight testing accelerated, and contractor personnel went to a three-shift work day.

New problems arose with each succeeding step into a higher Mach regime. The worst of these—one of the most formidable in the program’s history—was revealed when flight testing moved into speeds between Mach 2.4 and 2.8. The aircraft experienced such severe turbulence that it became nearly impossible to operate. The trouble was the air inlet system, which admitted air to the engine. At higher speeds, airflow was uneven, and the engine could not function properly. Only after a long period of experimentation was a solution reached.

Another, more mundane discovery was that nuts, bolts, clamps, and other debris of the manufacturing process that had not been cleared away were sucked into the engine on engine runup or takeoff. The engine parts were machined to such close tolerances that this could ruin them. Inspection procedures were revised, and workers at Burbank found it prudent to hoist the engine nacelles into the air, rock them back and forth, listen for loose objects, and then remove them by hand.

Keeping the Secret

On a routine flight on May 24, 1963, one of the detachment pilots recognized an erroneous and confusing airspeed indication and decided to eject from the aircraft. It crashed fourteen miles south of Wendover, Utah. The pilot was not hurt. The wreckage was recovered in two days, and witnesses were identified and requested to sign secrecy agreements. A cover story for the press described the accident as involving a F-105, and it is still listed this way on official records.

All A-12 aircraft were grounded for a week during investigation of the accident. A plugged pitot static tube in icing conditions turned out to be responsible for the faulty cockpit instrument indication. The problem would not hold things up for long.
Loss of this aircraft nevertheless exacerbated a policy problem that had been troubling the CIA for some time. With the growing number of A-12s, how much longer could the project remain secret? The Department of Defense was having difficulty concealing its participation because of increasing Oxcart expenditures. It also realized that the technological data would be extremely valuable in connection with feasibility studies for the commercial supersonic transport. Awareness grew in the aircraft industry that something new and remarkable was going on. Commercial airline crews had sighted the A-12 in flight.

In spite of all this, 1963 went by without any public revelation. President Lyndon B. Johnson was brought up to date on the project a week after taking office and ordered an announcement for the spring of 1964. At his press conference on February 24, he stated:

“ The United States has successfully developed an advanced experimental jet aircraft, the A-11, which has been tested in sustained flight at more than 2,000 miles per hour and at altitudes in excess of 70,000 feet. The performance of the A-11 far exceeds that of any other aircraft in the world today. The development of this aircraft has been made possible by major advances in aircraft technology of great significance for both military and commercial applications.”

The President’s reference to the “A-11” was deliberate. “A-11” had been the original designation for the all-metal aircraft first proposed by Lockheed; subsequently, it became the designation for the Air Force YF-12A interceptor that differed from its parent mainly in that it carried a second man for launching air-to-air missiles. To preserve the distinction between the A-11 and the A-12, nearly all concerned government and industry personnel had been briefed on the impending announcement.

President Johnson also said that “the A-11 aircraft now at Edwards AFB are undergoing extensive tests to determine their capabilities as long-range interceptors.” It was true that the Air Force had contracted in October 1960 for three interceptor versions of the A-12, and they were available by this time. When the President made his announcement, however, there were no A-11s at Edwards, and there never had been. Project officials had known that the public announcement was about to be made, but they had not been told exactly when.

Caught by surprise, they hastily flew two Air Force YF-12As to Edwards to support the President’s statement. So rushed was this operation, so speedily were the aircraft put into hangars on arrival, that heat from them activated the hangar sprinkler system, dousing the reception team awaiting them.
From then on, while the Oxcart continued its secret career at its own site, the A-11 performed at Edwards AFB in a considerable glare of publicity.

Going Operational

Three years and seven months after first flight, the Oxcart was declared ready for operational use at design specifications. The first long-range, high-speed flight occurred on January 27, 1965, when one of the test aircraft flew for an hour and forty minutes, an hour and fifteen minutes of that time above Mach 3.1. Its total range was 2,580 nautical miles with altitudes between 75,600 and 80,000 feet.

Two more aircraft were lost during this phase of the program. On July 9, 1964, Aircraft No. 133 was making its final approach to the runway when, at an altitude of 500 feet and an airspeed of 200 knots, it began a smooth steady roll to the left. Lockheed test pilot Bill Parks could not overcome the roll. At about a 45° bank angle and 200-foot altitude, he ejected. As he swung down to the vertical in the parachute, his feet touched the ground—one of the narrower escapes in the perilous history of test piloting. The primary cause of the accident was a frozen servo for the right outboard roll and pitch control. No news of the accident filtered out.

The next year, activity at the test site reached its zenith. Completion of construction brought it to full size. All detachment pilots were Mach 3.0–qualified. Site population reached 1,835. Contractors worked three shifts a day. Lockheed C-121 Constellations made daily flights between the factory at Burbank and the site, and there were two C-47 flights a day between the site and Las Vegas. Officials considered how, when, and where to use Oxcart in its appointed role.
All through the Oxcart program, the Air Force had been exceedingly helpful. It gave financial support, conducted the refueling program, provided operational facilities at Kadena AB, and airlifted Oxcart personnel and supplies to Okinawa for operations over Vietnam and North Korea. It also ordered from Lockheed a small fleet of A-11s, which upon being finished as two-seat reconnaissance aircraft would be named SR-71. These became operational about 1967.

The SR-71 order eased the path of Oxcart development because it meant the financial burden was shared with the Air Force, and the cost per aircraft was somewhat reduced by economies of scale. In the long run, however, the existence of SR-71s in a parallel fleet spelled Oxcart’s doom.

The Oxcart program lasted more than ten years, from its inception in 1957 through first flights in 1962 to termination in 1968. Lockheed produced fifteen Oxcarts, three YF-12As, and thirty-one SR-71s. The forty-nine supersonic aircraft completed more than 7,300 flights, with 17,000 hours in the air. More than 2,400 hours had been above Mach 3. Five Oxcarts were lost in accidents; two pilots were killed, and two narrowly escaped death. Two F-101 chase planes were lost with their Air Force pilots during Oxcart’s test phase.