a beast that was able to fly at three times the speed of sound

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When we travel by plane we go quite a lot (but quite fast). For example, the Boeing 737-800, which is the one used by Ryanair, is capable of traveling to a top speed of 946 km/h. Not bad, especially if we think about what an average car can achieve. But that figure, which is not exactly low, has nothing to do with that achieved by the fastest plane in the world: the Lockheed SR-71.

This aircraft, manufactured by the American Lockheed, flew through the skies from December 22, 1964 until 1998, when it was withdrawn. It is, to date, the fastest aircraft in the world and is capable of flying at Mach 3.32. What does that mean? 3,540 km/h at 24,000 meters. Three times the speed of sound.

A most curious work of engineering

Lockheed SR-71

The Lockheed SR-71, also known as the Blackbird, was a long-range strategic reconnaissance aircraft. It was developed by Blackheed as a “black project”, that is, a top secret project. In fact, it was a plane designed to avoid radar, although it was far from being completely invisible.

The plane had a cabin for two crew members, was 32.7 meters long, had a wingspan of 16.9 meters and had a height of 5.6 meters. Its empty weight was 30,600 kilos. (which is not little, especially if we take into account that an F-16C is 8,670 kilos) and the keys to flying at such speed were in its design, especially in the air intakes.

Lockheed SR-71

The air intakes had to adapt to huge changes in pressure and speed. To do this, a pointed cone located in the frontal of the motor (controlled by a first analog and then digital system) was in charge of keeping the incoming air at subsonic speed.

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The tine retracted up to 66 centimeters as the plane increased its speed. The pressure generated in the engine’s air intake was such that, at a speed of Mach 3.2, it was estimated that 58% of the thrust was generated by the higher pressure air intake. 17% was generated by the compressor and 25% by the afterburner.

Lockheed SR-71

However, flying at these speeds involves a significant rise in temperature. Up to 316ºC, to be exact, on the external surface. That, simply put, is enough to melt aluminum. How was it fixed? Using a structure of titanium alloy that, eye, was imported from the Soviet Union in the middle of the Cold War. The windows of the cabins, on the other hand, were made of quartz.

Such was the temperature reached by the aircraft that the fuselage panels were not fitted perfectly. Titanium expanded when heated, up to five centimeters, so you’d leave room. Basically, the plane didn’t fit perfectly until it warmed up. In fact, it was losing fuel before takeoff, so it had to take off, warm up, and be refueled.

Lockheed SR-71

The cabin interior was also problematic. The temperature inside could be up to 120ºC, so a heat exchanger was used to bring heat from the cabin to the fuel before combustion. As you can imagine, when the plane landed you had to wait a while to get close to the cabin, because it was hot.

And the landing gear? What about the wheels? Well, they weren’t like a car, obviously. The wheels were made of latex mixed with aluminum and filled with nitrogen. They reached a pressure ten times higher than what the wheels of our cars can have.

Lockheed SR-71

Curiosities aside, the edge was also key, that kind of “plate” that comes out of the cabin and expands to the sides. This peculiar edge, whose angle of incidence could be reduced, served to increase aircraft lift and its aerodynamic performance. In addition, it avoided using tail wings and, to this day, we can still see it on some UAVs (unmanned aerial vehicles).

Among his most interesting records are flying to 25,929 meters in sustained flight and reach a record speed of 3,540 km/halthough a pilot, Brian Shul, claims to have flown above Mach 3.5 (4,174.38 km/h) on April 15, 1986 to dodge a missile in Libya.

Have there been faster planes? Yes, rocket planes to be exact. The fastest has been the X-15, an experimental aircraft that in 1961 managed to reach 6,587 km/h at a height of 30,968 metres. Its first flight was on June 8, 1959 and it was withdrawn in December 1968.

When we travel by plane we go quite a lot (but quite fast). For example, the Boeing 737-800, which is…

When we travel by plane we go quite a lot (but quite fast). For example, the Boeing 737-800, which is…

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