Lockheed SR-71 Blackbird – The Plane Designed to Leak

Lockheed SR-71 Blackbird was a strategic reconnaissance aircraft developed for the United States Air Force.

For more than 20 years, this Lockheed plane served as the most important reconnaissance aircraft. SR-71 was designed to outperform every Soviet aircraft and missile with speed and altitude, following the 1960 incident, when the Soviets shot down CIA reconnaissance aircraft 1960 and captured its pilot Gary Powers.

Named Blackbird due to its unique blue to black color, this aircraft would set numerous world records for speed and altitude. Its small radar cross-section, paired with high speed, high altitude capabilities, and innovative defensive systems made the aircraft almost for radars. Blackbird was powered by two Pratt & Whitney J58 engines which provided a thrust of 32,500 lbf each.

It had a titanium body and incorporated the most innovative image and signals intelligence technology. Throughout its career, Blackbird would remain undefeated in the air, having escaped hundreds of enemy missiles and aircraft.

The A-12 Oxcart was only in service for 6 years.
The A-12 Oxcart was the forerunner to the similar SR-71.

Contents

Development

The development of the aircraft which would be known as SR-71 began after a request from the CIA in 1957 to build an undetectable plane that would outperform the CIA’s, U2 reconnaissance aircraft.

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Lockheed, which had designed and manufactured the CIA’s U2, immediately appointed Kelly Johnson and the Skunk Work unit to start sketching the models for the new aircraft.

Following numerous revisions requested by the CIA, Skunk Works prepared the aircraft model named A-12. This model would secure Lockheed a contract from the U.S. Government, and enable them to begin the work on developing and manufacturing the aircraft.

A rare sight to see these two birds together.
The SR-71 (right) parked next to the A-12 (left). Photo credit – Alan Wilson CC BY-SA 2.0.

On May 1st, 1960, the Soviet Air Defense Force managed to shoot down a U2 aircraft with surface-to-air missiles, capturing its pilot Gary Francis Powell and the majority of spying technology on the aircraft.

This incident served as an additional motive for Lockheed and the CIA to work on the development of the new aircraft. Lockheed’s task was to develop the fastest aircraft of that time, which would fly at extremely high altitudes and could not be intercepted by even the fastest Soviet aircraft.

The first variant of the plane named A-12 had its first flights on April 30th, 1962, proving worthy of the investment. Nevertheless, the development of the aircraft would continue. Considering the potential of the A-12, USAF ordered a reconnaissance variant that would be bigger than the A-12 and able to host more signals and intelligence equipment, in addition to a greater fuel capacity.

The SR-71 was far ahead of the East's aircraft technology.
The SR-71 was the very bleeding edge of technology and amazing considering its first flight was in 1964.

The aircraft would be designated SR-71 (SR- standing for strategic reconnaissance) and would complete its first flight on December 22, 1964. 

After another incident on October 27th, 1962, when another U2 was hit by Soviet surface-to-air missiles during the Cuban crisis, the idea of the plane became very simple. The Blackbird should be able to beat not only the attacks of adversary aircraft but also their missiles, using unmatched high speed and high altitude.

The plane was able to fly at 3 Mach, which was achieved on July 20, 1963, at an altitude of 78,000 ft.

If an aircraft or missile came close to the Blackbird, the aircraft would switch to flying at a higher altitude, leaving enemy aircraft unable to follow, and enemy missiles with exhausted thrust at high altitude. The aircraft would be painted in dark blue and black color to serve as camouflage in the night sky and to increase internal heat emission.

Is the SR-71 technically a spacecraft?
The view from the Blackbird at 83,000 feet.

The Skunk Works team had worked so intensively on the aircraft after the U.S. Government feared Soviet Radar advancements that the final model of the aircraft was very impressive.

On the test conducted in absolute secrecy in the Nevada desert, the aircraft which was 100 feet long, would appear on the radar slightly bigger than a bird, but smaller than a man. The radar cross-section had been reduced by 90% after repeated demands from the customer.

However, the whole process of bringing the aircraft to its final form required extensive work. Considering the demand for speed exceeding 3 Mach and the thermal heat’s effect on steel, Lockheed’s engineers preferred titanium for the structure of the aircraft over steel.

The SR-71 could reach 1,000 degrees fahrenheit.
The SR-71’s skin was titanium as it needed to withstand extreme heat.

The whole process of working with titanium was a separate challenge for the company. Firstly, securing the titanium required a complex acquisition process because the titanium ore was not available in the U.S.

The company would purchase the ore from the Soviet Union using a Third World country as a disguise.

Secondly, titanium was a very expensive metal, which increased the cost of the aircraft. Thirdly, Lockheed had to change most of its working methods because of titanium, including, using only distilled water and removing cadmium-plated tools due to their corrosive impact on titanium.

The SR-71 required sealed suits due to the extreme altitudes.
The crew before a flight. Looks almost alien.

Nevertheless, Lockheed’s Skunk Works ensured that titanium was the main structural component for the Blackbird while it used a quartz windscreen for the cockpit.

The aircraft was powered by 2 Pratt & Whitney J58 engines, which could produce a static thrust of 32,500 lbf (145 kN). The iconic large inlet shock cones would decrease the air’s speed as it entered the engine to subsonic speed. 

Surprisingly enough, the engines were the most efficient when the aircraft was flying at 3.2 Mach. Though some flights revealed it could be even more efficient at speeds exceeding 3.2 Mach. The only limitation for the speed of the aircraft was the air temperature entering the engine compressor.

These engines could propel the SR-71 to mind bending speeds.
The heart of the SR-71 the J-58 engines. Photo credit – Cobrachen CC BY 2.5.

However, with great speed comes high fuel consumption. Lockheed’s engineers made sure that the aircraft could be in-flight refueled considering that supersonic flights consumed an immense amount of fuel, and could last no more than 90 minutes.

The SR-71 was infamous for leaking fuel whilst on the runway too. Whilst being designed, the high temperatures and expansion of the materials used had to be taken into account and gaps were left to ensure this did not cause issues in flight. So whilst cold, the SR-71 constantly leaked. The titanium skin could reach almost 1000 Fahrenheit and that heat made the plane grow nine inches longer during a normal flight.

Considering that this aircraft was supposed to be a strategic reconnaissance marvel, great attention was paid to integrating the most cutting-edge technology. The Blackbird had two seats in its cockpit, with the pilot sitting in the front, and the navigator/reconnaissance systems officer sitting in the back.

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The aircraft would contain the SLAR – side-looking airborne radar and ELINT – electronic intelligence gathering systems with options to record for both systems. In addition, the Blackbird would carry both Fairchild and infrared cameras and imagery systems.

The world's first "selfie"?
Brian Shul taking a “selfie” in the cockpit of the SR-71.

The aircraft would also be equipped with defensive systems including electronic countermeasure systems and jammers that made the aircraft almost impossible to be intercepted or hit.

Considering the heat generated by the high speed of the aircraft and the decrease in pressure due to high-altitude flights, the cockpit and pilots were equipped with custom-made equipment for protection if exposed to extreme conditions.

The cabin would regulate the pressure and heat to the personnel’s benefit, while they would also be given special pressurized suits and masks.

Lockheed would produce 32 units of SR-71 aircraft, 29 of which were the standard A variant, 2 were trainer variant B, and 1 was a hybrid trainer C variant.

NASAs SR-71s.
A pair of SR-71As and an SR-71B (middle). Photo credit – NASA CC BY 2.0.

Operational History

With only 32 aircraft manufactured, Blackbird had an impressive operational history all over the world. On March 1968, SR-71s would be deployed to Okinawa, Japan as part of the 9th Strategic Reconnaissance Wing.

From there they would conduct reconnaissance missions over North Vietnam, which were initially codenamed “Black Shield” and later on “Giant Scale”. Normally, SR-71s were designated to conduct 1 sortie per week, as they had a long turnaround after mission recovery.

They required constant maintenance and repairs due to the extreme conditions in which the airplane operated. However, by 1970, the demands for intel in North Vietnam had risen forcing the use of SR-71s twice a week.

KC-135Q refueling an SR-71A.
The ability for inflight refueling was extremely important to the success of SR-71 missions.

By 1972, SR-71s were required to perform daily reconnaissance missions over North Vietnam and Laos. The extensive use of Blackbird might be the reason for 2 of these aircraft getting lost in missions in 1970 and 1972, which were attributed to mechanical malfunctions. Nevertheless, Blackbird emerged victorious in all engagements with North Vietnam adversaries.

There were around 800 surface-to-air missiles fired at SR-71s with all of them being unable to hit the aircraft. During its time in Okinawa Japan, the plane would receive its second nickname after the Japanese pit viper, called locally “Habu”, which the locals thought the aircraft resembled.

On the other side of the planet, SR-71s would be used to conduct reconnaissance operations over the Soviet bloc.

The SR-71 cockpit.
The cockpit of the SR-71 does not have a touchscreen in sight.

They would operate out of England, on two main routes. The first one was over the West coast of Norway to the Soviet Kola Peninsula, while the other was over the Baltic Sea. The first route was considered safer since Norway was a NATO member and could be used for an emergency landing if they encountered troubles in flight.

The second route was slightly more complex. The SR-71s were constantly spotted and tracked by Swedish Air Force’s radars, which lead the route followed by SR-71s to be named the Baltic Express by the Swedish Air Force.

Eventually, there would be a benefit from being spotted by the Swedish Air Force. On June 29th, 1987, a Blackbird’s engine would explode very close to Soviet airspace. The explosion and loss of altitude would give away the position of the damaged Blackbird.

Close up of an SR-71B cockpit.
Both the SR-71B and A-12 needed to have special cockpit glass to endure the high tempreatures.

The plane was spotted by the Swedish Air Force, who send two JA-37 Viggen planes to observe the situation. The Blackbird changed the course and was headed for a Swedish island to do an emergency landing. The Viggens immediately understood the situation and escorted the plane until another pair JA-37s took over and sent it to safety.

Declassified documents revealed that there were many MiG-25 Foxbats in the air ordered to shoot the Blackbird down, with one Foxbat having its missiles locked on the Blackbird. In 2018, the Swedish pilots would receive the USAF medal for their contribution to saving the plane. In 1990 the Blackbird would retire without having been shot down by an enemy.

The Soviets were scared of what the SR-71 was capable of.
The MiG-25 was tasked with taking out the Blackbird. The Soviet Union was aware of the danger this new aircraft posed.

For numerous political and technical reasons, the Blackbird would retire in 1990. Some politicians and experts named the operational and maintenance costs as the main reason to retire the plane, which presented inflated values to back their claim.

Some other critics claimed the lack of datalink (unavailability of live feed) and substitute technology such as UAVs and Satellite imagery as the reason for the SR-71 to retire. However, the capabilities and technology of SR-71 were still very important and unmatched in 1989.

That was the case with General Norman Schwarzkopf’s request for expedited reconnaissance, which could not be fulfilled because the SR-71s were retired.

Even the MiG-25 would have struggled to catch an SR-71.
The SR-71 would have been difficult to catch in a MiG-25.

Until its first retirement, the Blackbird family had flown 53,490 total flight hours, of which 11,008 were mission flight hours.

The plane would come out of retirement to serve in the Bosnian War, after a request from senior military leadership and hearings in the US Congress. This time, Lockheed would equip it with a datalink for near real-time transmission. Only three SR-71s would return to service. 

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Retirement

The plane would finally retire in 1998, after a long period of controversy regarding funding dedicated to the aircraft. Many were afraid that SR-71s might attract funding and attention from newly developed UAVs. NASA would continue using the Blackbird until 1999.

The SR-71 was important to NASA research.
NASA continued to use the Blackbird almost 10 years after retirement by the USAF.

Today, the surviving SR-71s (12 were lost in different missions) can be found all over United States’ Museums. The National Museum of the United States Air Force, Wright-Patterson Air Force Base hosts the SR-71 aircraft that flew a record of 942 total sorties. One SR-71 is also exposed in American Air Museum in Britain, Imperial War Museum Duxford, Cambridgeshire, England.

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Specifications

  • Crew: 2; Pilot and reconnaissance systems officer (RSO)
  • Length: 107 ft 5 in (32.74 m)
  • Wingspan: 55 ft 7 in (16.94 m)
  • Height: 18 ft 6 in (5.64 m)
  • Wheel track: 16 ft 8 in (5 m)
  • Wheelbase: 37 ft 10 in (12 m)
  • Wing area: 1,800 sq ft (170 m2)
  • Aspect ratio: 1.7
  • Empty weight: 67,500 lb (30,617 kg)
  • Gross weight: 152,000 lb (68,946 kg)
  • Max takeoff weight: 172,000 lb (78,018 kg)
  • Fuel capacity: 12,219.2 US gal (10,174.6 imp gal; 46,255 l) in 6 tank groups (9 tanks)
  • Powerplant: 2 × Pratt & Whitney J58 (JT11D-20J or JT11D-20K) afterburning turbojets, 25,000 lbf (110 kN) thrust each
  • Maximum speed: 1,910 kn (2,200 mph, 3,540 km/h) at 80,000 ft (24,000 m)
  • Service ceiling: 85,000 ft (26,000 m)
  • Rate of climb: 11,820 ft/min (60.0 m/s)