For as long as I’ve loved airplanes, I remembered reading about the SR-71. The Blackbird, an icon in aviation history. This plane, built in the 1960’s, still holds top speed and altitude records, unconquered even by the billion dollar productions of the F-22 Raptor, F-35 Lightening II, and the Concorde. Of course, building such a magnificent beast didn’t come without challenges. I’ll be going over the forces of physics, politics, design, and the USSR the SR-71 had to overcome in its journey to glory.
Wait, but why?
The origin story of the SR-71 starts with a single aviation incident: the U-2. In the 50’s, the U-2 “Dragon Lady” was the US Air Force’s primary plane for reconnaissance missions, during which secret aerial photographs would be taken above enemy territory. However, in 1960, at the onset of the Cold War, a U-2 plane was shot down over Soviet Union, its pilot and surveillance footage captured. Soon, people realized that at the speed the USSR was making advances in their radar and missile technology that the U-2 would be more and more prone to similar attacks. The Dragon Lady had met its match: the plane was becoming obsolete.
Following the incident, President Eisenhower asked Lockheed Martin, the manufacturer of the U-2 plane, to design a new reconnaissance plane that would be faster, higher, better. He wanted the plane to never be able to be shot down — he wasn’t disappointed. The impossible task was given to the Advanced Development Group, codenamed SkunkWorks, at Lockheed Martin. An engineer at the group named Clarence “Kelly” Johnson, would eventually become a renowned aerospace engineer and the leading contributor of the entire Blackbird project. In February 1960, the CIA signed a $96 million contract with Lockheed Martin for the production of 12 Blackbird planes. The project was a go.
Turbulence ahead
Designing an aircraft that flew faster and higher than ever before while staying, literally, off-the-radar, and be able to take pictures at the same time? Not an easy task.
Heat was an issue. In order for the Blackbird to fly at Mach 3, or 3 times the speed of sound, the front of the aircraft would be exposed to temperatures up to 1,000 degrees Fahrenheit, or 500 degrees Celsius. This is due friction from the air molecules colliding with the leading edges of the aircraft, converting their potential energy into thermal energy — heat. Hence the faster you fly, the higher temperatures the plane will be subject to. However, remember that the plane will be flying at 70,000 ft, where the temperature outside is -67 degrees Fahrenheit (-55 degrees Celsius). This means that parts of the plane will be in extreme heat while other parts are subject to extreme cold. The solution that Lockheed Martin engineers came up with was surprisingly simple — black paint. SkunkWorks’ Ben Rich remembered an elementary lesson from school: the colour black both emits and absorbs heat, hence it is great at distributing heat across a surface. Hence the plane was painted black (actually a very dark blue), and received the name, Blackbird.
The engineers also built the plane using 90% titanium alloy due to its light weight but more importantly its resistance to high temperatures. At the time (and now as well), it was extremely rare for airplanes to be composed of such a high percentage of titanium: most were used only on leading edges of wings and nose. However, the drawback of using titanium was that it was extremely brittle:
It was said that the first batch of heat-treated titanium alloy parts were so brittle, that they would shatter if you dropped them from your desk
Furthermore, it was discovered that on assembly lines, the steel tools workers normally used would damage the brittle titanium material as well. As a result, every tool in the engineer’s arsenal had to be reproduced in titanium just for the manufacturing of the Blackbird. Ironically, the USSR was the largest supplier of titanium in the world. So in order for the US to produce the Blackbird, they had to obtain the titanium through bogus companies and third world countries. In the end, the USSR ended up ‘sponsoring’ the program that would go on to surveil their own country.
Off-The-Radar
Another key goal of the program was stealth: the ability to appear as small as possible on radar. To meet that goal, the shape of the Blackbird was groundbreaking at the time, with its smooth surfaces and rounded curves. Its black paint was embedded with iron ferrite particles, which helped absorb radar. The Blackbird even used a special fuel that contained Cesium to attempt to reduce exhaust fumes to avoid detection. They accomplished this by creating a cloud of plasma behind the plane that absorbs electromagnetic waves, preventing them from being bounced back to the ground.
There are many many more challenges engineers faced when designing this groundbreaking plane. For example, designing new suits and masks for the crew to provide life support in high-speed and high-altitude ejections; manufacturing new tires and chutes customized for the Blackbird, and even creating a new tanker aircraft that re-fuels the Blackbird at very high speeds. There’s a huge rabbit hole of interesting problems that we won’t talk about today, but I encourage you to research more!
1962: Blackbird is off to the races
In April 1962, the Blackbird flew for the very first time. This is actually not the SR-71, but its predecessor A-12.
Eventually, three variants were created from the A-12. The first, named YF-21 was an interceptor plane armed with Air-to-Air missiles for the USAF. This program never went past its prototype stages into operation. The second variant, called M-21, was designed as a drone carrier. It had a pylon on the top where the drone is deployed from. But the program was also cancelled after a drone crashed with the aircraft mid-flight, killing one pilot. The third variant was the SR-71, which stands for Strategic Reconnaissance. As opposed to the single-seater A-12, the SR-71 had two seats so that a Reconnaissance Systems Officer in the back can handle the navigation and camera equipment, while the pilot in the front doesn’t have to worry about anything aside from flying. This was very crucial to reducing the heavy workload of the single pilot in the A-12. Additionally, the SR-71 also had more fuel capacity added. However, as a result of the added passenger and fuel, a lot of the surveillance equipment on the SR-71 had to be downgraded to adjust for the additional weight. Now, we have a plane optimized for the US Air Force: the first SR-71 Blackbird took to the skies in December of 1964.
SR-71 Blackbird: the Michael Phelps of the 1960's
After the SR-71 entered service in 1966, it started breaking every. single. record. It was, and still is, the fastest jet in the world, with a cruising speed of Mach 3.3, and reports of pilots flying the Blackbird up to Mach 3.5. For comparison, commercial airliners like the Boeing 737 or Airbus A380 has top speeds of around Mach 0.8. The Concorde, the only supersonic commercial jet, had a top speed of Mach 2. Even the most advanced fighter jets today like the F-22 or the F-35 max out around Mach 2 as well.
Top-speeds:
Similarly, the SR-71 broke altitude records with its service ceiling at 85,000 ft. Again, for comparison, commercial airlines generally need to stay below 45,000 ft. The aircraft it replaced, the U-2, had an operational ceiling of 60,000 ft. Fighter aircrafts today also usually below 50,000 to 60,000 ft. Although to be fair, these aircrafts have very different design goals than the SR-71 did back then.
Service ceiling:
As a result of the extreme capabilities of the SR-71, none were ever shot down. There are many interviews with SR-71 pilots where they said they simply change direction and accelerated to literally outfly missiles. MiG-25’s, Soviet Union’s fighter jets at the time, also stood no chance. SR-71’s were truly a badass in the skies.
However, there was a price to pay. The plane was notorious for being unreliable — often planes would come back missing rivets or parts, or needing some kind of repair. This meant the turnaround time for the planes was long: averaging only one flight a week during its service. Although no planes were shot down, 12 of the 34 SR-71’s produced were lost in accidents due to mechanical failure, tire explosions, even one stall as a result of severe weather. The planes, from production to takeoff, also needed an army of people and resources. The teams compared each takeoff to a rocket launch — if there’s a mission now, the Blackbird will be off the ground in 19 hours. To just start the plane, a “start cart’ is needed to connect to each engine and help them get to the minimum 3000 RPM for it to become self-sustaining. Usually planes would take off with very little fuel to reduce the stress on its tires and brakes, and needed to be refuelled in the air immediately after takeoff.
Flying the SR-71 was no easy task either. The nose had to be maintained within 1 or 2 degrees of the prescribed angle to keep it stable, meaning the aircraft is constantly at the edge of losing control. The engines also ran into a common issue known as an “unstart’. On the SR-71, the inlet cone can actually move backwards up to 3 feet to position its shockwave to minimize drag. If the cone is in an incorrect position, it can actually cause the shockwave to blow out the front of the inlet.
This often caused the afterburner to be extinguished, leading to a very violent yaw from the thrust produced from the afterburner on the other side that’s still running. This was very dangerous, and led to the crash of one of the planes.
Retirement
The USAF SR-71 program was closed down in October 1989, with the last Blackbird making its final flight from LA to Washington D.C., breaking 4 flying records in the process, making it from coast to coast in 64 minutes. There are many widely disputed theories on why the SR-71 went out of service. Many people said it was because it was too expensive. Each SR-71 had a price tag of 34 million, or $280 million today. And although it’s widely disputed, some say it cost up to $200,000 an hour to operate. The fuel alone burned through $37,000 an hour — much faster than burning cash! Others also said it was because of the unreliability and slow turnaround time of the airplane. It’s important to also look at the politics at the time. When the program was thriving in the 70’s and 80’s, many of the SR-71 squadron and wing commanders were promoted into high positions in the Air Force, where they did a great job of showcasing the value of the program to Congress. However, in the late 80’s most of these generals had retired, and there were less and less people to advocate for the program. Instead, the new generation of generals wanted to cut the program to fund new bomber initiatives, for example the development of the B-2. The Air Force also did not see the intelligence the program generated as very valuable, which was seen as more valuable for the CIA and NSA.
NASA actually flew 2 Blackbirds in 1999 to research high-altitude and high-speed flight. Most of the surviving SR-71’s, sadly, live in museums today.
Legacy
So what follows the legacy of SR-71’s today? The majority of air reconnaissance is conducted by Unmanned Aerial Vehicles, or drones. The US Air Force currently operates a large arsenal of RQ 11 Ravens UAV’s. There were rumours that Lockheed Martin is working on an UAV called SR-72 that will be flying at Mach 6, twice as fast as the Blackbird. But as far as manned aircrafts goes, it sounds like most developments will not be looking to push the reconnaissance limits the SR-71 once set.
Thanks for reading the first instalment of my new series, Airplane Anatomy! In this series I’ll be breaking down different aircrafts from their first production to their final flight, with engineering, physics, and even history sprinkled in. Most of all tho, it will be me fangirl-ing about airplanes. Woohoo!
