In the last Top Engineering Achievements blog we looked at the famous International Space Station and how engineers contributed to its success. This time, we look at another airborne achievement, the Lockheed Martin SR-71 'Blackbird'.
The Blackbird is in our top engineering achievements series for three reasons: it still retains the record for the fastest and highest manned aircraft ever created; it was successfully launched after such a short time-period; and the amount of aerospace engineering innovations and challenges that were overcome that contributed to its success. Another example of how #EngineersRule! Read more below about this special aircraft.
What is the SR-71 Blackbird?
Due to a U-2 aircraft being shot down during the Cuban Missile Crisis in 1962, the US Airforce needed a more effective reconnaissance aeroplane.
Lockheed Martin’s famous Skunk Works in California started to work on a plane that could fly faster and higher than previous models, along with minimal radar detection, allowing it to map terrain, and interrupt enemy communications and radar signals.
It was a ‘black project’, which meant it was a highly classified military defence development. Famous aircraft engineer Kelly Johnson helped to lead the project, and successfully did so in just 20 months.
The first aircraft produced was the single-seated A-12, which first flew in April 1962. The larger SR-71 was soon produced and took its first flight in December 1964. The plane was nicknamed ‘Blackbird’ given its reconnaissance, colour, and apparent quietness within the cockpit.
The Blackbird is still the world’s fastest and highest-flying manned aircraft. The speed record was broken in 1972 with a record of 2,193mph and an altitude of 85,069 feet. At this height, pilots could see the curvature of the earth and black space above.
Other aircraft can reach these speeds but only for a brief period, whereas the SR-71 could easily operate safely at speeds of Mach 3.3.
The key to the Blackbird’s success was a combination of its high altitude and incredible speed. If an anti-aircraft missile was detected, the usual procedure for the Blackbird was to simple accelerate and out-fly it.
A total of 32 Blackbirds were built and 12 were lost in accidents, but none were ever lost due to the actions of enemy forces.
How did engineers contribute to the SR-71?
The Blackbird is believed to be the most technologically advanced aircraft ever built in terms of the technology available at the time. The aircraft was so far ahead of its time and the engineers working on the project broke many barriers to enable to project to be rolled out on time.
Due to the speed of the aircraft, new materials and techniques were required to deal with the immense temperatures created, sometimes exceeding 538°C. As a result, titanium alloy was used as a shell to protect the aluminium airframe. The surface was also designed to ensure that the Blackbird was barely detectable by radar. The engines were moved to a mid-wing position and the paint contained a radar-absorbing element.
To stop the tires from melting on the Blackbird, aluminium was mixed with latex and then filled with nitrogen. The tyre pressure on the SR-71 was an incredible 415psi, compared to 32-35psi in the average car.
The distinctive ridges on its fuselage were originally an experiment in radar stealth but it was then discovered these helped with lift when at speeds of Mach 1 or above. This also gave the Blackbird’s shape great manoeuvrability, but its engines wouldn’t allow for tight-turns so they were forbidden. Special engine inlets were used to slow the air down to subsonic speeds before it entered the jet engines.
The aircraft also used a bespoke fuel called JP-7 due to the extremely high operating temperatures, which the aircraft burned 18-22 tons of fuel per hour of flight. The fuel was even formulated to have low radar detectability with the inclusion of Cesium.
What’s next for the Blackbird?
The SR-71 was officially retired from the US Airforce in 1998 and from NASA in 1999.
However, Lockheed Martin’s Skunk Works revealed the SR-71’s successor in late 2013. The SR-72 will be designed for a Mach 6 cruise speed, twice that of the SR-71, and will have the optional capability to strike targets. It could enter development as early as 2018 and become operational in 2030.
Aviation Week, who originally broke the news, explains:
“Guided by the U.S. Air Force's long-term hypersonic road map, the SR-72 is designed to fill what are perceived by defense planners as growing gaps in coverage of fast-reaction intelligence by the plethora of satellites, subsonic manned and unmanned platforms meant to replace the SR-71. Potentially dangerous and increasingly mobile threats are emerging in areas of denied or contested airspace, in countries with sophisticated air defenses and detailed knowledge of satellite movements.”
Although we aren’t recruiting for Skunk Work’s SR-72 project, we still have some exciting engineering and technical jobs for you to take a look at.