Designed in the late 1950s, the Blackbird is an absolute miracle in aviation history.

© National Air and Space Museum

Leviathan Press:

It is not an exaggeration to describe the A-12/SR-71 as "out of this world" - especially considering that it was born in the 1950s, its status is even more prominent. Kelly Johnson, who was able to design this epoch-making work, naturally deserves credit. Kelly Johnson is of Swedish descent. Lockheed boss Hall Hibbard once said to Ben Rich (Ben Rich, the designer of the famous F-117 stealth fighter): "That damn Swede can actually see the air." This is the highest praise I have ever heard for an aviation designer.

On September 1, 1974, U.S. Air Force pilots Major James Sullivan and Major Joel Widdifield took off from New York and flew east across the Atlantic Ocean. When they arrived in London, it took only 1 hour, 54 minutes and 56 seconds, which was less than one-seventeenth of the flight time of Charles Lindbergh 47 years ago.

This impressive feat, which still stands as a world record, is attributed to the aircraft flown by Sullivan and Widdifield: a Lockheed SR-71 Blackbird.

This sleek, bizarre-looking aircraft is a flying sensation in almost every sense of the word. Capable of flying at three times the speed of sound at an altitude of more than 27 kilometers, faster than even air-to-air missiles, it remains the fastest military aircraft ever to enter service.

No other reconnaissance aircraft in history has been able to fly in the world's most dangerous airspace without being disturbed by any threat like the SR-71. © National Air and Space Museum

But what mission was this plane designed for? And what made it fly so fast? Let's take a deeper look at the incredible engineering of one of the most technologically advanced aircraft in history.

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The Blackbird’s story begins in 1958 with Clarence “Kelly” Johnson, then chief engineer at Lockheed’s Advanced Design Projects Office, better known as the Skunk Works.

Founded in 1939, Skunk Works was named after the fictional moonshine factory "Skonk Works" in cartoonist Al Capp's popular comic strip "Li'l Abner." The factory soon became known for its innovative and groundbreaking aircraft designs, including the P-38 Lightning fighter and the P-80 Shooting Star, the United States' first mass-produced military jet.

A Lockheed F-104 of the US Navy in 1960. © Vintage Aviation News

Lockheed U-2 "Dragon Lady" reconnaissance aircraft. © Palm Springs Air Museum

In 1954, the Skunk Works unveiled two of its most iconic aircraft, which were conceptually very different: the F-104 Starfighter and the U-2 Dragon Lady. Nicknamed the “Manned Missile,” the Starfighter had a narrow, tapered fuselage, short, sharp wings, and powerful J79 turbojet engines that enabled it to reach twice the speed of sound and climb to an altitude of 25,000 meters in just 4.5 minutes.

The U-2, by contrast, was a reconnaissance aircraft designed not for speed but for altitude. Essentially a jet glider, the U-2 had a 24-meter wingspan and could cruise at altitudes above 20,000 meters—well beyond the range of Soviet anti-aircraft missiles at the time. However, this exceptional performance came at a price. At altitude, the difference between the stall speed and the critical Mach number was only a few knots, meaning that any sudden change in speed while climbing or descending could cause the aircraft to tumble out of the air. This dangerous flight state, known to pilots as the "Coffin corner," made the U-2 one of the most difficult aircraft to fly in the world, and those who could fly it were generally considered the best pilots in the world.

U-2 reconnaissance aircraft, operated by the CIA from bases in West Germany, Alaska, Japan, and Pakistan, began flying regularly over Soviet territory in 1956, using powerful cameras to photograph air and naval bases, missile launch sites, weapons factories, and other strategic targets. U-2 flights revealed that the Soviet Union's advantage in strategic weapons - the so-called "bomber gap" and "missile gap" - was actually a myth. U-2 also captured evidence that triggered the 1962 Cuban Missile Crisis.

Initially, it was believed that Soviet radars could not track the U-2, but this assumption was soon proven wrong, and multiple Soviet interceptors and missiles attempted to shoot down these high-altitude intruders, but all were unsuccessful. Although various attempts were made to reduce the U-2's radar cross section, these measures were mostly ineffective and greatly reduced the aircraft's flying altitude, making it more vulnerable to attack. As Soviet air defense capabilities continued to improve, it was only a matter of time before the U-2 was unable to perform its mission.

In response, in 1958 CIA officer Richard Bissell launched Project GUSTO, a committee chaired by Polaroid chairman Edwin Land, whose task was to discuss possible successors to the U-2. The committee met seven times between November 1957 and August 1959, with representatives from major aircraft manufacturers, including Lockheed's Kelly Johnson. Johnson declared of the next generation of strategic reconnaissance aircraft:

“There’s no point in just pushing current technology one or two steps forward because we’ll only buy a few years and then the Russians will beat us again… I want us to have an aircraft that can rule the skies for a decade or more. ”

Johnson said the new aircraft should be able to cruise at 3-4 times the speed of sound and at an altitude of more than 30,000 meters. In this way, it can not only escape the attack of any manned interceptor and surface-to-air missile, but also avoid detection by exploiting the weakness of early radar systems (i.e., the spot scan ratio). In simple terms, if the aircraft flies faster than the radar refresh rate, it will be filtered out as background noise, making it almost impossible to detect.

Starting in 1958, several manufacturers began submitting proposals for such aircraft, ranging from the fanciful to the truly bizarre. For example, the U.S. Navy proposed an aircraft capable of flying at Mach 4, using a ramjet engine and launched from a nuclear submarine. Ramjets are very efficient at high speeds, but rely on forward motion to function and cannot accelerate from a standstill. Therefore, the Navy planned to launch the aircraft into the air via a giant helium balloon, and then accelerate it to cruising speed via rocket boosters. However, when Kelly Johnson of Lockheed analyzed the design and found that the balloon would have to be close to two kilometers in diameter, the Navy withdrew the proposal.

Convair's "first stealth Super-Hooter" prototype. © Reddit

Convair's proposal, called the First Invisible Super Hustler (FISH), was slightly less ambitious. Using two ramjets and capable of cruising at Mach 4, FISH was a stowed aircraft that was planned to be launched from a Convair B-58 Hustler bomber. To withstand the enormous frictional heat encountered at hypersonic speeds, the nose and wing leading edges were made of a special material (high-temperature ceramic) developed by Corning Glass Works.

Lockheed's original CL-400 Suntan proposal. © Reddit

Lockheed's original proposal, the CL-400 Suntan, was a bit more exotic. The "Suntan" resembled an enlarged version of the F-104 Starfighter, powered by a pair of ramjets mounted on the wingtips, burning pure liquid hydrogen. The liquid hydrogen was stored in the fuselage tanks and delivered to the engines through pipes on the leading edge of the wings, preheating the fuel and cooling the fuselage.

However, the GUSTO committee was not satisfied with these initial proposals and asked the bidders to resubmit designs based on the Pratt & Whitney J58 turbojet engine, which had been developed in 1958 and used in several aircraft projects but never entered service. Lockheed's new design, codenamed "Archangel", was still powered by a ramjet, but used conventional fuel and was boosted to cruising speed by the J58 engine in full afterburner mode.

J58 engine testing. © CIA

Meanwhile, Convair resubmitted a design, the Kingfish, which was no longer air-launched, had a top speed of 3.2 times the speed of sound and a range of nearly 6,300 kilometers. Although the GUSTO committee liked Lockheed's design, they considered its radar cross section too large. This prompted Kelly Johnson to gradually improve the design, eventually forming the A-11, which reduced the original radar cross section by 90%.

A-11 design. © wikipedia

Finally, on August 28, 1959, the government announced that Lockheed had won the contract for the new reconnaissance aircraft. The decision was based not only on the aircraft's performance estimates, but also on Lockheed's previous track record of completing projects on time and at low cost. In contrast, Convair had a long history of budget overruns and did not have a secret project department comparable to Lockheed's "Skunk Works". In January 1960, the CIA placed a $96 million order for 12 A-11s, which were humorously named "OXCARTs".

The decision came at the right time, because just four months later, the day the US military had been dreading finally arrived.

A U-2 spy plane from Bridge of Spies (2015). © Spirituality & Practice

On May 1, 1960, CIA U-2 pilot Francis Gary Powers took off from Peshawar, Pakistan, and flew northwest toward the Soviet border. Powers' mission was to fly approximately 6,000 kilometers over Soviet territory, photographing various targets, including the Baikonur and Plesetsk cosmodromes, and the Chelyabinsk-65 plutonium production plant, before landing in Bodø, Norway. The flight went smoothly at first, and the Soviets attempted to intercept Powers with conventional jet fighters, but were unsuccessful. However, shortly after flying over Chelyabinsk, he was eventually shot down by an S-75 surface-to-air missile near the city of Sverdlovsk. Powers managed to parachute and land on the ground, where he was subsequently captured by Soviet authorities and displayed to the world.

The 1960 U-2 incident caused an international scandal and severely damaged US-Soviet relations. It also marked the end of the US flying over Soviet territory, resulting in a serious shortfall in its military intelligence collection on the Soviet Union. At the time, Lockheed was developing its CORONA series of spy satellites, but the technology would take another year to mature.

Meanwhile, the Skunk Works continued to push forward with the A-11. The challenge facing Kelly Johnson's engineers was enormous, forcing them to rethink nearly every aspect of the aircraft's design. As Johnson later said:

"Everything had to be invented. Everything."

The A-11 must fly under extremely harsh conditions: when the aircraft flies at three times the speed of sound, the friction with the atmosphere will generate a surface temperature of more than 500 degrees Celsius - enough to melt the traditional aluminum alloy fuselage. Therefore, 93% of the A-11 parts are made of titanium alloy, because titanium is not only twice as dense as aluminum, but also has far better heat resistance than aluminum.

But there was a small problem: in the late 1950s, titanium was scarce, and the world's largest source of titanium was... you guessed it: the Soviet Union. While the CIA managed to obtain a large amount of Soviet titanium through a network of shell companies, if it only purchased the high-grade titanium that Lockheed needed, it would risk alerting the Soviets to its end use. So the CIA was forced to import hundreds of tons of mixed grades of titanium, of which Lockheed only selected about 7% for use in aircraft manufacturing.

Kelly Johnson poses in front of a YF-12A interceptor (serial number 60-6934). © Lockheed Martin

But the challenges are far from over.

Because titanium is an extremely difficult material to machine, regular cadmium-containing tools would make the metal brittle and cause it to chip when in contact, so new titanium tools had to be made. Once, body bolts and other fasteners began to fail for no apparent reason, it was discovered that all the wrenches in the factory also contained cadmium, forcing a careful examination of every toolbox to identify the offending tool. Then there were the welds, which were cracking almost randomly. Further investigation revealed a strange pattern: Winter welds were working fine, while summer welds were prone to premature failure.

After months of relentless investigation, it was eventually traced to the water supply in Burbank, California, where the Lockheed factory is located. In the summer, the city added more chlorine to the water to prevent algae growth; when newly welded titanium parts were washed in this high-chlorine water, the welds became brittle. When Johnson ordered the welds to be cleaned with distilled water, the problem disappeared.

At the bottom of the air intake cone of the A-12 (60-6924/933) in the American Aviation Museum, the deformation and bulging of the skin on the fuselage surface can be clearly seen. © Prime Portal

However, just as Lockheed had mastered the technology of titanium manufacturing, another equally troublesome problem arose. Frictional heating during high-speed flight caused the aircraft's external panels to expand and deform, damaging the fuselage structure. To solve this problem, Lockheed engineers replaced the flat skin with a fine corrugated skin to make it less likely to deform when expanding.

The corrugated skin is concentrated at the rear of the A-12. © Pin page

Some engineers have likened the technique to flying a 1930s Ford Trimotor or Junkers 52—the planes known for their corrugated skins—at supersonic speeds. The skins are also made slightly smaller than their actual size so that the edges fit together precisely after they expand due to heat.

The fuel leak problem has long been ridiculed by the outside world as a major design flaw in the A-12. But in fact, no sealant can withstand the extreme heat generated by an aircraft above Mach 3, so it is impossible to keep the fuel tank sealed. © X

To save weight, the outer skin doubles as the siding for the fuel tanks, which leads to a worrying design quirk: fuel leaks out like a sieve when the aircraft is parked on the tarmac. In practice, standard procedure is to fill only enough fuel for takeoff, and the aircraft will then rendezvous with an aerial refueling tanker for refueling. When the aircraft reaches operating speed and altitude, thermal expansion causes the skin to expand and seal itself, preventing further fuel leakage.

As you can imagine, fuel leaking onto the tarmac would be a fire hazard, so the Skunk Works developed a special high-flashpoint fuel called JP-7 that would not ignite with an open flame or spark. However, since JP-7 also could not be ignited by conventional jet engine igniters, Lockheed developed a system to inject diborane (a gas that self-ignites when in contact with air) into the engine to ignite this fuel. The engines were started before takeoff by a special starter cart, which housed two Chevrolet big-block engines with an output of 600 horsepower.

The moment the car is ignited. © Preserving our History

The extreme temperatures encountered at Mach 3 meant that nearly every system on the aircraft had to be specially designed. Special lubricants and hydraulic fluids were developed to withstand temperatures up to 350 degrees Celsius, while the fuel system was designed to circulate through the JP-7 fuselage to cool those hot parts. Control cables are made of a high-temperature steel-chromium-nickel alloy called Elgiloy (commonly used for clock springs). All electrical connections are even plated with gold, because gold can maintain its conductivity better than other metals at high temperatures.

Coping with the extreme temperatures of flying at speeds above Mach 3 is the most daunting challenge. © Osprey Publishing

Weight restrictions meant the cockpit couldn't be insulated, forcing pilots to wear special air-conditioned pressurized suits that also protected them from the near-vacuum of the stratosphere. In fact, it could get so hot inside the cockpit under cruise conditions that crews often heated up their meals by leaning them against the cockpit glass during missions.

Pratt & Whitney J58 turbojet engine, Evergreen Aviation Museum. © wikipedia

At the request of the GUSTO committee, the A-11 was powered by two Pratt & Whitney J58 turbojets, which had to be extensively modified to operate reliably with afterburners turned on and to withstand the extreme conditions of flying at three times the speed of sound.

© Nickel Alloy

The engine itself is mounted in a streamlined wing nacelle, which at cruising speeds acts partly like a ramjet, diverting most of the incoming air into the annular space between the engine and the nacelle. Since a jet engine cannot inhale air at supersonic speeds or it would stall, the nacelle inlet has a special cone that creates a shock wave that slows the incoming air to subsonic speeds before it enters the engine.

But no matter how fast the A-11 flew, it was useless as a reconnaissance aircraft if it couldn't take clear pictures. As a result, engineers put considerable effort into the fused quartz window of the onboard aerial camera. Due to the temperature difference of up to 500 degrees Celsius between the inside and outside of the aircraft, this window was prone to optical distortion, which could ruin any photos taken through it. This problem once caused great anxiety for the design team until Corning Glass Works developed an innovative method to use powerful high-frequency sound waves to fuse the glass to the titanium frame. The camera itself, built by Perkin-Elmer, could carry 1,500 meters of film and could take ground images up to 113 kilometers wide from an altitude of 30,000 meters with a resolution of 30 centimeters.

A-12 (60-6925), mounted inverted, for radar wave testing. © CIA

In November 1959, before the first prototypes began production, Lockheed built a full-scale mockup of the A-11 and shipped it to Groom Lake, Nevada (better known as Area 51), where it was mounted on a pylon and subjected to radar waves from all angles. These tests showed that the aircraft's radar cross-section was still unacceptably high, forcing Lockheed to make further changes to the design.

The first batch of A-12 Oxcart flight photos released by the CIA. The adjustable air intake cone is clearly visible. © CIA

These modifications included replacing the leading edges of the wings and tail with a radar-absorbing composite material made of iron oxide, silica, and asbestos; and blending the fuselage and wings with sharp fin-like structures called chines, giving the aircraft an otherworldly appearance. Aviation historian Peter Merlin once described it this way:

"...it looks more organic than mechanical. Most conventional aircraft look like they were built by humans - this one looks like it grew naturally."

A-12 design. © wikipedia

It was later discovered that, in addition to reflecting radar, the ridgeline had the added benefit of providing additional lift at supersonic speeds. In light of these modifications, the aircraft's designation was changed from A-11 to A-12, a designation it still bears today.

Overcoming these unprecedented technical difficulties was both expensive and time-consuming. Delivery of the first prototype was initially promised for May 1961, but as development progressed, that date was pushed back to August, and the first flight was delayed to December. Meanwhile, the $96 million budget had ballooned to more than $161 million. Richard Bissell, then a senior CIA official (and then caught up in the aftermath of the Bay of Pigs), wrote a distraught letter to Kelly Johnson:

"I have been informed of a further delay in your first flight from August 30 to December 1, 1961. This news is all the more shocking in addition to our previous delay from May to August, and according to our meeting of December 19, I had thought that the titanium extrusion problem had been largely solved. I am sure that unless there is a serious earthquake in Burbank, this will be the last of the disappointing news."

However, there was even more disappointing news for Bissell. Due to the ultra-advanced materials and manufacturing technology involved, the A-12 could not be mass-produced like conventional aircraft. Each aircraft could basically be said to be a hand-made work of art. In July 1961, Johnson wrote in his journal:

“… The process of building the first aircraft was very difficult… Everyone was nervous… and we still have a long way to go.”

To control costs and get the project back on track, the CIA cut the order from 12 to 10 and sent an aeronautical engineer to Lockheed to oversee final assembly. Meanwhile, Pratt & Whitney was having serious problems getting the J58 engines up to Lockheed's specifications. To prevent delays, Pratt & Whitney decided to use the less powerful J75 engine used on the U-2 for the first test flight. In theory, this would allow the A-12 to reach an altitude of 15,000 meters and a speed of Mach 1.6.

At the same time, the CIA was looking for future A-12 pilots. The criteria were almost as strict as those for selecting the first U.S. astronauts, the Mercury 7: Candidates had to be qualified to fly high-performance jets, be between 25 and 40 years old, be no taller than 6 feet (1.83 meters), and weigh no more than 175 pounds (79 kilograms) to fit into the A-12's cramped cockpit.

They also had to pass a rigorous series of medical examinations and undergo interviews designed to assess their political reliability and emotional stability. By November 1961, the first 12 pilots had been selected. Like the pilots who flew the U-2, these men formally resigned from the military and became CIA contract employees with an agreement that they could later return to active duty without loss of rank or seniority—a practice known as “wool washing.”

A-12 is being packed for transport. © CIA

Finally, on February 28, 1962, the first A-12 prototype was loaded into two large boxes and transported by road from the Skunk Works in Burbank to Groom Lake for flight testing. Since no self-respecting pilot wanted to fly an airplane named "Oxcart," the test pilots named the strange new aircraft "Cygnus," after the star constellation.

The A-12 made its first flight on April 25, 1962. © wikipedia

On April 24, Lockheed test pilot Lou Schalk was conducting a high-speed taxi test when the A-12 unexpectedly became airborne for a few seconds, completing its first flight (albeit briefly). The next day, the A-12 made its first official (albeit still unofficial) flight, with Schalk again at the controls. Just 20 seconds after takeoff, the aircraft began to shake violently; Schalk chose to land the aircraft on the dry lake bed at the end of the runway rather than circling it.

As the A-12 came to a stop, Schalk heard Kelly Johnson's angry roar over the radio: "Lou, what the hell is going on?"

The next day, Schalk conducted another informal test flight, but he did not retract the landing gear to prevent the possibility of another forced landing. At first, the flight went smoothly, but soon the leading edge of the aircraft's wings began to fall off titanium pieces. It took Lockheed technicians several days to find these pieces in the dry lake bed and reinstall them on the aircraft. Nevertheless, Johnson was very satisfied with the results, saying:

"We confirmed that the first flight failure was not caused by the basic stability of the aircraft."

Finally, on April 30, the A-12 made its first official flight in front of Air Force and CIA representatives—a year later than originally planned.

The A-12 practically spawned its own industrial base: some 2,400 machinists, mechanics, and fabricators could do their own milling and forging. The slogan “FOD Eliminate” can be seen in the image above, which stands for “Foreign Object Damage Eliminate,” a reference to engine failures that are sometimes caused by small objects that are accidentally dropped and left inside the nacelle during the manufacturing process. © CIA

From then on, flight testing progressed steadily, with the second A-12 joining the test in June 1962. On May 2, the A-12 broke the sound barrier for the first time, reaching a top speed of Mach 1.1. However, without the right engine, the A-12 would never reach its full potential. The CIA thus put more pressure on Pratt & Whitney, and finally in January 1963, the first J58-powered A-12s began to take to the air. At the same time, the world situation also made it clear that an aircraft like the A-12 was urgently needed. On October 27, 1962, U-2 pilot Rudolph Anderson was shot down and killed while photographing Soviet ballistic missile facilities in Cuba. With the impact of this event, the A-12 project entered the fast track, and Lou Schalk made the first Mach 3 flight on July 20, 1963.

A-12 taking off. © Imgur

By 1966, the A-12 was regularly breaking world records in aviation—albeit secretly and unofficially. On December 21, for example, Lockheed test pilot Bill Park flew the plane north from Groom Lake over Yellowstone National Park to Bismarck, North Dakota; then east to Duluth, Minnesota; south to Atlanta and Tampa; northwest to Portland; and finally southwest over Knoxville and Memphis back to Nevada—all in just six hours, covering 10,000 miles.

The only two-seat A-12. © wikipedia

For pilot training, one A-12 was converted into a two-seater. Nicknamed the "Titanium Goose," the trainer used a lower-powered J75 engine to save the scarce and expensive J58 engines for combat aircraft. Although the A-12 was originally bare titanium, in 1964 the fuselage was painted with the iconic black coating to better dissipate heat.

While flight tests showed Kelly Johnson’s titanium wonder to be a fundamentally sound design, it remained a difficult and sometimes dangerous aircraft to fly. The first crash of the A-12 occurred on May 24, 1963, when pilot Ken Collins was forced to eject near Wendover, Utah, after his instruments failed. Collins was not injured, and the wreckage was quickly collected and secretly transported away, with locals who witnessed the crash forced to sign nondisclosure agreements. The cause of the crash was ice on the pitot tube.

A persistent problem encountered during flight testing was that the shock wave formed by the engine intake cone tended to separate, causing the engine to starve of fuel and cause a violent deceleration that the pilots described as "getting caught in a train crash." This problem threatened the smooth progress of the entire project, and it took several months for engineers to perfect a system that could automatically retract the intake cone and "recapture" the shock wave in an instant.

A total of 2,850 test flights were made at Groom Lake before the A-12 was finally put into service, and three more aircraft were lost. The first occurred on July 9, 1964, when the pitch control servo froze, causing the aircraft to lose control. Pilot Bill Parker ejected safely and was rescued. The second occurred on December 28, 1965, when pilot Mele Vojvodich experienced a series of violent yaw and pitch movements shortly after takeoff and had to eject. The cause of the accident was believed to be a gyro in the stability augmentation system that had been miswired by a maintenance technician. The last occurred on January 5, 1967, when an A-12 crashed on approach to the Groom Lake runway due to fuel exhaustion. Pilot Walter Ray ejected successfully, but the seat failed to detach, causing him to fall to the ground and die - the first fatal accident in the A-12 program. The cause of the accident could not be determined, but investigators suspected a malfunction in the fuel indication system.

Although the A-12 was designed as an unarmed reconnaissance aircraft from the beginning, its amazing performance made many people imagine its other potential uses. For example, General Curtis LeMay, commander of the Strategic Air Command, considered using the A-12 as a high-speed nuclear bomber to strike deep enemy targets; while the Air Force top brass imagined that the A-12 could become a high-altitude, high-speed interceptor to shoot down Soviet strategic bombers, or a larger, longer-range reconnaissance aircraft to assess target damage after a nuclear strike.

Lockheed YF-12A (60-6934), the first of three prototypes. © US Air Force

A Hughes AIM-47A guided missile is prepared to be loaded into the YF-12A's weapons bay. © US Air Force

Although LeMay's bomber was never built, two variants were developed for the Air Force. Designated the YF-12, the interceptor was equipped with a second cockpit for the weapons system operator, the AN/ASG-18 fire control system, and AIM-47A air-to-air missiles, with the front edge of the fuselage removed to accommodate the radome.

Three YF-12 prototypes were built, with the first flight taking place on August 7, 1963.

Early YF-12A (60-6935) fuselage was mostly bare titanium, not covered with black coating. © Reddit

An Air Force RS-71 (left) and a CIA A-12. © Reddit

The second Air Force variant was designated RS-71, RS standing for "Reconnaissance/Strike", and was in fact a larger and more complex version of the A-12. It was one meter longer than the A-12, weighed 6,800 kg, had a 13% increased range, and was equipped with a reconnaissance cockpit as well as additional photography, synthetic aperture radar and ELINT sensors. The RS-71 first flew on December 22, 1964, painted in the same black paint as the A-12, earning it the immortal nickname "Blackbird".

M-21 flying with D-21. © Reddit

Another spinoff of the A-12 program was the Lockheed D-21, an autonomous ramjet-powered drone designed to conduct reconnaissance deep into enemy territory. Built using many of the same materials and technologies as the A-12 and RS-71, the D-21 was launched from the back of a specially modified A-12 mothership, known as the M-21. Once launched, the D-21 would fly over enemy territory at speeds of Mach 3.3 and an altitude of 29,000 meters, using an inertial guidance system for navigation and an advanced camera system to photograph enemy targets. It would then fly over international waters and release film canisters by parachute, which were grabbed from the air by a Lockheed C-130 transport aircraft. While this procedure may sound overly complicated today, this method had been perfected to great effect in recovering film canisters from the CORONA spy satellite.

Two A-12s were converted to serve as M-21 carriers, and flight testing began in March 1966. Results from the first three test flights were mixed, with the D-21 experiencing various system failures. The drone also exhibited a disturbing state of hovering above the carrier fuselage for a few seconds after launch. As a result, launches were performed while flipped in sideways flight to help the drone separate from the carrier. The test program was abruptly aborted on July 30, 1966, when the D-21 suffered an engine failure immediately after launch and struck the tail of the carrier, forcing the M-21 crew to eject. Pilot Bill Parker survived, but launch controller Ray Torick accidentally opened his helmet visor as he parachuted into the sea, causing water to enter his protective suit and dragging him into the sea.

After the disaster, plans to launch the M-21 were abandoned and the D-21 was instead launched from a Boeing B-52 strategic bomber, accelerated to cruising speed by solid rocket boosters. This configuration proved to be much safer, and in November 1969, the Air Force launched Operation Senior Bowl, an attempt to use a D-21 drone launched from a B-52 to reconnaissance China's Lop Nur nuclear test site. From November 9, 1969 to March 20, 1971, a total of six Senior Bowl missions were carried out, with disappointing results. Two drones failed to reach their targets and crashed, two successfully released film canisters but were lost in the sea, and the film canisters of the other two were successfully recovered. However , most of the photos were destroyed due to improper film processing techniques. In July 1971, the D-21 project was finally cancelled.

During the development of the A-12 and its derivatives, the U.S. government faced an increasingly vexing question: How long could the program remain secret? Rising costs made it increasingly difficult for the Defense Department to deny the existence of the A-12, while airline pilots and other witnesses frequently saw the mysterious aircraft on test and training flights in the American Southwest.

A-12 and its derivatives. © California Science Center

Despite the efforts of Lockheed, the CIA, and the Air Force to keep the project secret, the truth would eventually come out. Moreover, Lockheed knew that its cutting-edge research in supersonic aerodynamics would have a huge impact on the aviation industry, especially in the design of the Supersonic Transport (SST) - the predecessor to Concorde. Eventually, they devised a plan to manage the public information, and on February 24, 1964, President Lyndon B. Johnson announced it to the nation:

"The United States has successfully developed an advanced experimental jet aircraft, the A-11, which has been continuously flight tested at speeds in excess of 2,000 mph and altitudes in excess of 70,000 feet. The performance of the A-11 far exceeds that of any other aircraft currently in the world. The development of this aircraft has benefited from major advances in aircraft technology and has significant implications for both the military and civilian sectors. Several A-11 aircraft are currently undergoing flight testing at Edwards Air Force Base in California to determine their capabilities as long-range interceptors."

Five months later, Johnson spoke again, declaring:

“…successfully developed a new strategic manned aircraft system to be used by the Strategic Air Command. Using the new SR-71 aircraft, the system provides a long-range advanced strategic reconnaissance aircraft for military use, capable of providing global coverage for military operations… The SR-71 is the most advanced in the world. The aircraft will fly at speeds in excess of three times the speed of sound. It will operate at altitudes in excess of 80,000 feet and utilize a variety of the most advanced sighting equipment in the world. This aircraft will provide America’s strategic forces with superior long-range reconnaissance capabilities.”

Johnson chose his words carefully. For example, the use of the name A-11 (the original name of the A-12 before it received radar-evading improvements) was a misdirection designed to confuse potential spies. Moreover, by publicly acknowledging the existence of the similar-looking YF-12, the hope was that the A-12 could continue to be kept secret. For the time being, the strategy seemed to work, as dozens of aviation journals and other publications wrote exhaustive articles about the ultra-advanced "A-11" based on the small amount of technical information the government chose to declassify. Meanwhile, the A-12's testing and training program continued in relative secrecy.

A Lockheed A-12 "Oxcart" and YF-12A at Groom Lake, Nevada. © CIA

However, the secrecy had unintended consequences. When President Johnson first made the announcement in February, there were no YF-12s at Edwards Air Force Base. The Air Force was caught off guard and hastily flew two prototypes to Edwards to support the president’s claims. The move was so hasty that when the planes were wheeled into the hangar, the heat from the fuselages triggered the sprinkler system, drenching the committee members.

Johnson's second speech also left an unexpected legacy. Although the Air Force's official designation for the A-12 derivative was the RS-71, Johnson mispronounced it as the SR-71. The Air Force decided it would be easier to rename the aircraft than to publicly correct the president's name, so it went with the SR-71.

In 1967, a full five years after its first flight, the A-12 finally entered service. By this time, however, the mission for which it was originally designed had disappeared. After the downing of Francis Gary Powers in 1960 and Rudolf Anderson in 1962, the U.S. government abandoned manned flights over Soviet and Cuban territory as too politically risky. That mission was instead taken up by CORONA spy satellites, which by 1967 were regularly sending back high-quality photographic intelligence. As a result, the A-12 was repurposed as a tactical reconnaissance platform for gathering up-to-the-minute intelligence in active war zones—such as the conflict then underway in Vietnam.

An image of military facilities in Hanoi taken by an A-12 during Operation Black Shield. © CIA

In 1967, the U.S. military was concerned about reports that North Vietnam had acquired a large number of medium-range surface-to-surface missiles from the Soviet Union, believing that these missiles could be used to attack South Vietnam. In response, the CIA launched Operation Black Shield to assess North Vietnam's missile capabilities. In May 1967, three A-12s flew from Groom Lake to Kadena Air Base in Okinawa, Japan, crossing the Pacific Ocean in just 5 hours and 55 minutes. The unit was declared officially operational on May 30, and the next day, pilot Mel Vojvodich flew the first Black Shield mission, flying at a speed of Mach 3.1 and reaching an altitude of 24,000 meters, filming a nearly 2-kilometer-long film strip covering most of North Vietnam and the demilitarized zone between the North and the South. To the great relief of the Pentagon, this and subsequent missions showed that North Vietnam did not have surface-to-surface missiles.

Over the next seven months, the A-12 flew 22 Black Shield missions, photographing artillery positions, factories, supply depots, ports, radar facilities, prisoner-of-war camps, and other strategic targets. This intelligence was crucial in President Johnson's approval of a massive air campaign against North Vietnam. However, despite its advanced stealth characteristics, the A-12 was often detected by North Vietnamese search radars. Radar technology had improved significantly since the A-12 was designed, and many of the A-12's stealth features were of limited use in practice.

On October 28, an A-12 was attacked for the first time, but the missiles failed to lock onto the target. Two days later, pilot Denny Sullivan was nearly hit over Hanoi when a North Vietnamese SAM launch site fired at least six missiles at him. He later recalled:

"All of a sudden a big ol' telephone flies right past the cockpit, straight up. I thought, this is pretty interesting... and I continued on my route and didn't see anything until I was a little way out, and I looked in the rearview mirror and saw at least four missile trails, all spreading out and heading towards my tail. I thought, 'Gosh, these things fly pretty well.' I watched them catch up... behind me, very close, and then all of a sudden there's this huge red ball of fire, followed by a white cloud of smoke - you immediately have to pull away. You're going 41 miles a minute. These SAMs are very well guided and do the exact same thing."

Although the A-12 had a top speed of Mach 3.2 and the Soviet-made S-75 surface-to-air missile could reach Mach 3.5, Sullivan managed to avoid the attack and returned safely to Kadena. Upon returning to the base, maintenance personnel found a missile fragment embedded in the wing near a fuel tank. This was the only time the A-12 was damaged by weapons in combat.

On January 23, 1968, a North Korean torpedo boat attacked and captured the USS Pueblo, a U.S. Navy spy ship operating in international waters. Fearing that this incident could spark war, the CIA sent Jack Weeks on a reconnaissance mission to North Korea three days later in an A-12. This and a subsequent flight showed that Pyongyang had not mobilized its military for war. As a result, President Johnson canceled plans for a punitive strike against North Korea in favor of a diplomatic solution that resulted in the release of the Pueblo's crew less than a year later. Meanwhile, five more Black Shield missions were flown over North Vietnam and Cambodia.

Just as the A-12 was beginning to demonstrate its combat value, its combat career came to an abrupt end. With the defense budget stretched thin by the Vietnam War, the U.S. government could no longer fund the A-12, YF-12, and SR-71, three very similar aircraft programs.

YF-12A (60-6936) takes off from Edwards Air Force Base during speed record trials on May 1, 1965. The white cross on the belly of the aircraft was to assist timekeepers and observers. © CIA

As relations with the Soviet Union improved, the importance of North American air defense decreased, and the YF-12 project was canceled. In November 1967, the Air Force launched Operation Nice Girl, a formal flying duel between the A-12 and the SR-71 to determine which aircraft was the superior reconnaissance aircraft. Over three days, the two competing aircraft flew the same route from California to Louisiana, taking off one hour apart, performing a variety of tasks including photographing designated targets and aerial refueling. Although the results were inconclusive, the SR-71 was ultimately declared the winner due to its more advanced sensor systems and longer range.

After the A-12 was retired, it was exhibited in aviation museums around the world. © Space camp Programs

Other factors may have influenced the decision, as the Air Force was known to be jealous of the CIA's A-12 program and wanted to take full control of high-speed military aviation into its own hands. Regardless, after just 10 months of service, the A-12 was retired and all subsequent Black Shield missions were flown by the SR-71. Of the 15 A-12s produced, three flew 29 Black Shield missions, while six were lost in accidents, killing three pilots. The remaining nine aircraft were stored in Palmdale, California, and remained top secret for the next nearly 20 years. After the A-12 program was declassified in 1981, the aircraft were removed from the hangars and distributed to museums across the United States, where they are still on display today.

While the A-12 was lost in the dustbin of history, the SR-71 quickly became one of the most famous aircraft in the world, breaking dozens of aviation records.

World speed record holders and Thompson Trophy winners Colonel Robert L. Stephens and Lieutenant Colonel Daniel Andre. © Space camp Programs

For example, on July 28, 1976, Captain Robert Helt broke the world absolute altitude record, reaching 26,929 meters. On the same day, another SR-71 broke the absolute airspeed record at 3,529 kilometers per hour (about Mach 3.3). Two years earlier, on September 1, 1974, James Sullivan and Noel Widdifield flew the 5,570 kilometers from New York to London in just 1 hour, 54 minutes and 56 seconds, with an average speed of 2,908 kilometers per hour (about Mach 2.72). And even earlier, on April 26, 1971, Thomas Estes and Dewain Vick flew 24,000 kilometers in just 10 hours and 30 minutes. This flight won them the Mackay Trophy in 1971 and the Harmon Trophy in 1972.

It is important to note that while other aircraft flew faster and higher, these achievements were achieved under very specific conditions. For example, on August 22, 1963, pilot Joseph Walker reached an altitude of 108 kilometers while flying, breaking through the edge of space, while on October 3, 1967, William "Pete" Knight set a speed record at 7,274 kilometers per hour (Mach 6.7). However, both pilots were flying North American X-15 rocket-powered experimental aircraft, which were launched after being dropped from a mother aircraft at high altitude.

SR-71 pilot Brian Shull in the cockpit. © Smithsonian Magazine

Earth as seen from the cockpit of an SR-71, about 83,000 feet. © Smithsonian Magazine

In contrast, the SR-71 set all of its records in level flight using its air-breathing engines after taking off from the ground under its own power. While the SR-71's predecessor, the A-12, could technically fly higher and faster, it was shrouded in secrecy throughout its service life and was therefore ineligible to compete for international aviation records. Likewise, while SR-71 pilot Brian Shul claimed to have reached Mach 3.5 dodging surface-to-air missiles over Libya on April 15, 1986, this record was never confirmed and therefore remains unofficial. For these reasons, the SR-71 is officially recognized as the fastest and highest-flying jet aircraft ever built, with records set in the 1970s still standing today.

But the SR-71 accomplished much more than breaking records and turning heads at air shows.

Since entering service in 1966, the Blackbird has participated in dozens of armed conflicts around the world, gathering vital intelligence during the 1973 Yom Kippur War, the Israeli invasion of Lebanon, and the 1986 US airstrikes on Libya. Between 1977 and 1988, the SR-71s based at RAF Mildenhall in the UK flew 322 so-called Baltic Express missions along the northern coast of the Soviet Union and East Germany—often violating Swedish airspace in the process. The Swedes responded by sending in supersonic fighters to defend their neutrality, but the SR-71 was much faster than these interceptors and never successfully intercepted any. It was even used domestically by the FBI in 1971 in the hunt for mystery hijacker DB Cooper.

An SR-71 at Kadena Air Base in Japan. © Reddit

All SR-71s were flown by the 9th Strategic Reconnaissance Wing, which was based at Beale Air Force Base in California but deployed to various operating locations, including Eielson Air Force Base in Alaska, RAF Mildenhall, Diego Garcia in the Indian Ocean, and Kadena Air Base in Okinawa, where the SR-71 received its second primary nickname: Habu, a reference to the aircraft's resemblance to a local venomous snake.

© The Aviation Geek Club

Flying the SR-71 was an extremely unique status, with a total of 93 Air Force pilots being certified as "sled drivers." This uniqueness made perfect sense, as the SR-71 was extremely difficult and often dangerous to fly. Of the 32 airframes built, none were lost to enemy action, but 12 were destroyed in various accidents.

"I don't think the odds of surviving an ejection at Mach 3.18 and 78,800 feet are very high." - Test pilot Bill Weaver © Reddit

However, only one crew member died while flying the Blackbird: Jim Zwayer, a Lockheed expert in testing reconnaissance and navigation systems. On January 25, 1966, his plane broke apart in the air during a test flight. Although the pilot, Bill Weaver, miraculously survived the plane's breakup and parachuted safely to the ground, Zwayer's neck was broken and he died on the spot.

Dennis Bush crashes his SR-71 at Kadena Air Base in Okinawa in 1972. © Reddit

SR-71 (61-17974) departs from Kadena Air Base on a mission on April 21, 1989. While accelerating to three times the speed of sound, the left compressor bearing freezes, causing the left engine to disintegrate immediately. Both pilots eject. © Reddit

By the late 1980s, the SR-71 had flown more than 3,000 sorties and accumulated more than 11,000 flight hours, more than a quarter of which were at Mach 3.

However, like the A-12 before it, the government decided to retire the SR-71 just as it was beginning to show its capabilities.

The official reason was mainly budgetary. The SR-71 was an extremely complex and expensive aircraft that required a large support staff and a global network of air bases, refueling aircraft, and other infrastructure. In fact, then-Secretary of Defense Dick Cheney estimated that the SR-71 cost as much as $85,000 per minute to fly, and the entire project cost about $300 million per year. At the same time, opponents believed that the same mission could be accomplished more efficiently by advanced spy satellites and drones. And ironically, the SR-71 was designed to replace the Lockheed U-2. Although the SR-71 was superior to the U-2 in almost every way, it had one major drawback: the lack of a data link system, which prevented the collected intelligence from being transmitted and used in real time.

Meanwhile, the U-2 had been upgraded with this system, though it was more vulnerable to air defenses. Supporters argued that the SR-71 offered unique capabilities unmatched by other reconnaissance platforms, but the aircraft was eventually retired in October 1989. As with the A-12, the decision was likely partly political, with the Air Force using the cancellation of the SR-71 program as a bargaining chip to secure funding for higher priority programs, such as the Boeing B-2 Spirit stealth bomber.

SR-71A and SR-71B trainer aircraft (center), Edwards Air Force Base, California, 1992. © wikipedia

The timing of this decision proved to be rather unfortunate, as the tactical reconnaissance capability provided by the SR-71 was greatly needed by Allied forces during the 1991 Gulf War. Similar intelligence gathering difficulties were encountered during the Bosnian War (1992-1995), and the SR-71 program was re-evaluated. Since no technology could match the SR-71's capabilities, Congress approved $72 million to reactivate three SR-71s and equip them with real-time datalink systems to bring them up to modern standards.

However, this brief comeback did not last long. The Air Force did not budget for the SR-71's reactivation, fearing that the decision would divert funding from other more important programs. Despite the Air Force's attempts to shut down the program, Congress approved the required funding. In October 1997, then-President Bill Clinton attempted to use his line-item veto to defund the program, but the Supreme Court quickly rejected the proposal as unconstitutional. Thus, the future of the SR-71 was left up in the air...

It wasn't until September 1998 that the Air Force finally reallocated the funds for the resumption of flight and completely retired the SR-71.

The retired SR-71 continues to serve NASA. © NASA

But this is not the end of the Blackbird story.

Because two Blackbirds were sent to NASA as hypersonic test beds. The two Blackbirds were also used to test rocket engine components for the Lockheed Martin X-33. The last flight of the SR-71 was in 1999, and the surviving aircraft were subsequently sent to aviation museums for display. This marked the end of an era. To date, no manned conventional aircraft has flown so fast and so high.

The Darkstar jet featured in the film "Top Gun: Maverick" was recently displayed at Edwards Air Force Base. Lockheed Martin currently insists that the mockup built for the film is fictional and that the SR-71 remains the "fastest recognized aircraft" in existence, sparking rumors of a successor, the SR-72. © Lockheed Martin

An original Lockheed Martin SR-72 concept drawing similar to the fictional "Dark Star" model from the film Top Gun: Maverick. © Lockheed Martin

Today, drones are increasingly taking over the Blackbird’s role, as they can be deployed more quickly and hover over targets longer without endangering the lives of pilots. However, no drone currently in use can match the Blackbird’s incredible speed—which allowed it to outrun all adversaries for nearly three decades—not even missiles.

But that may be about to change, as Lockheed is currently developing an unmanned successor, called the SR-72 "Son of Blackbird," whose scramjet engine will allow it to cruise at six times the speed of sound—twice as fast as the SR-71. The SR-72 is expected to enter service in the 2030s.

While the Blackbird no longer soars, its influence lives on today. Many of the aerodynamic and radar-evading technologies developed with the SR-71 and its predecessor, the A-12, found their way into the design of other aircraft, such as the supersonic Concorde and modern stealth aircraft like the F-117 Nighthawk, F-22 Raptor, and F-35 Lightning II. The Blackbird's unique shape was also the inspiration for Marvel's X-Fighter. The design is still used in today's movies, a testament to the forward-thinking vision of Kelly Johnson and Lockheed Skunk Works.

© Reddit

Although it was designed in the late 1950s, the Blackbird still looks like something from the distant future.

By Gilles Messier

Tempura

Proofreading/Rabbit's Light Footsteps

Original article/www.todayifoundout.com/index.php/2024/09/how-did-the-sr-71-blackbird-get-made-and-how-was-it-so-fast/

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