SR-71 "Blackbird"

Before I proceed, I first need to give credit where credit is due. Being an aviation enthusiast, over time, I plan to write a series of hubs on some of my favorite aircraft. This is an idea that was sparked when I read fellow “hubber” Wayne Brown’s excellent write-up on the venerable C-130 "Hercules". So a sincere "Thank Ya" to WB for the idea, and an invitation to you my appreciated reader to check out his hub (after you're done with mine, of course ;) by following this link:

http://hubpages.com/hub/THE-MIGHTHY-C-130-HERCULES

The Lockheed SR-71 “Blackbird” began it’s storied life as the A-12, a secret project developed for the CIA by Clarence “Kelly” Johnson at the Lockheed Skunk Works in Burbank, California. This firm is directly responsible for the design of many other notable aircraft, as well, such as the WWII era P-38 “Lightning”, the U-2 spy plane, the F-117 “Nighthawk”, and the F-22 “Raptor”.

The single seat A-12 was designed as a strategic reconnaissance platform to replace the U-2, which had proven vulnerable to U.S.S.R. SAM (Surface to Air Missile) emplacements. It was capable of much higher altitudes and speeds, as well as able to carry a much larger payload of surveillance equipment. Flight testing first took place on April 25, 1962 at the Groom Lake Air Force base (otherwise known as “Area 51”). While initial testing of the CIA’s A-12 went well, it’s production was later cancelled in favor of the upgraded Air Force version, then known as the R-12. This version included a longer fuselage to accommodate more fuel, a second seat in the cockpit, and redesigned “chines” along it’s leading edge and wing surfaces. Upon it’s official acceptance into the U.S. Air Force in 1964, the R-12 was re-designated as the SR-71.

A total of 32 SR-71s had been completed in 1968 when then Secretary of Defense, Robert McNamara ordered that the highly specialized tooling required to form the titanium structures of the Blackbird’s airframe be destroyed. This bone-headed move (in my humble opinion) not only effectively killed any chance of additional aircraft ever being built, but also prevented the production of repair and replacement parts, forcing maintenance crews to cannibalize existing planes to keep the diminishing fleet operational.

The Blackbird incorporates many design features which, to say were “innovative” even by today’s standards, would be an extreme under-statement, at best. For starters, due to the immense heat created at her cruising speed well in excess of mach 3 (three times the speed of sound, or roughly 2,300 MPH), Lockheed engineers had to utilize a mixture of 85% titanium and 15% composite materials in the construction of the SR-71’s skin, a first in the aircraft industry. One interesting point, the majority of the titanium used in construction of the Blackbirds was purchased directly from the U.S.S.R., the very nation the aircraft was designed to spy on! 

Because of the heat related expansion at speed, this skin was also required to be fitted in panels that were necessarily “loose” on the ground. Once up to operational speed, the corrugated shape of these panels would allow them to expand and attain a precise fit, but on the ground, they would actually cause the Blackbird to leak fuel. To counter this, pilots undertaking a mission would get airborne with a limited quantity of the specialized JP-7 jet fuel and, once up to operating temperature, would then meet up with a refueling tanker to top off the tanks.

Probably one of the most innovative features of the SR-71 was her very engines, the Pratt and Whitney J58-P4.

The SR-71, in order to fulfill it’s mission requirements, needed a very complex solution to a simple problem. How do you design an engine which is both operational at slower speeds while also being efficient enough at higher speeds for long range operations? The answer… enter the J-58. Referred to as a “hybrid” engine, the J-58 effectively functions as both a traditional turbojet engine for low speed flight, as well as a ramjet for efficient high speed operations. Using the unique moveable cones seen over it’s inlet ports, an onboard computer regulates airflow into and through the engine to both regulate pressure and insure a subsonic airflow for the turbojet portion even at supersonic speeds, as well as dictate which “half” of the engine is used under the appropriate circumstances. The J-58 produces a peak output of approximately 32,500 lbs. of thrust and is the first U.S. engine to be designed for continuous use in afterburner, as well as certified for speeds in excess of Mach 3.

Due to the exterior design of the Blackbird and these unique engines, she actually became more efficient the faster she went, reaching a top speed typically quoted as "Mach 3.2+". One relatively unknown fact, though, is that her top speed was actually only limited by the fact that, using the technology available at the time, fuel delivery to the engines had to be restricted on account of the specific maximum temperature for the compressor inlet of 800 *F. It is widely believed that, using today’s more advanced understanding of metallurgy; the engines could be built to withstand much higher temperatures. This could, in theory, allow the Blackbird to operate at speeds in excess of Mach 6.

Another challenge facing engineers, or more specifically, the pilots, was that, at such high airspeeds and altitudes as high as 85,000 feet, typical flight suits of the time simply were not up to the task. The three major problems were providing enough oxygen at such high altitudes to remain conscious, protection from the immense heat generated at such high speeds (at Mach 3, the interior glass of the cockpit would reach temperatures of over 250 degrees *F!), and survival in the event of a bailout. To overcome these problems, a special flight suit was designed by the David Clark Company which not only protected the SR-71 pilots, but was found to be so effective that it was later adopted by NASA for space shuttle crews.

The SR-71 Blackbird’s functional military lifespan lasted from it’s first recorded flight on December 22, 1964 through it’s controversial retirement upon completion of it’s final mission oreinted flight in 1989. In 1993, due to growing unease over rising tensions both in North Korea and the Middle East, the SR-71 enjoyed a short lived comeback. It’s capabilities allow it to provide real time and ongoing intelligence and reconnaissance data that spy satellites and other airframes are simply incapable of.

Unfortunately, it’s reinstatement was constantly sabotaged by politics as well as civilian contractors and lobbyists fearing their funding for competing projects would be cut. In 1997, then president Bill Clinton signed a line-item veto cancelling Blackbird funding, but it was overturned by the Supreme Court.

Sadly though, opposition remained relentless, and in light of this, the program was ultimately cancelled as of 1998. Fearing the SR-71s would potentially be called to service once again in the future, antagonists within the Air Force quickly ensured the remaining fleet of Blackbirds were donated to military and aviation museums around the country. As of today, the last two flight worthy examples are maintained by NASA’s Dryden Flight Research Center.

To this day, the SR-71 still retains the world record for the fastest manned jet aircraft at Mach 3.3. Some other notable speed related records, as per Wikipedia:

1. Los Angeles, Ca. to Washington, D.C., distance 2,299.7 miles (3,701.0 km), average speed 2,144.8 miles per hour (3,451.7 km/h), and an elapsed time of 64 minutes 20 seconds.
2. West Coast to East Coast, distance 2,404 miles (3,869 km), average speed 2,124.5 miles per hour (3,419.1 km/h), and an elapsed time of 67 minutes 54 seconds.
3. Kansas City, Missouri to Washington D.C., distance 942 miles (1,516 km), average speed 2,176 miles per hour (3,502 km/h), and an elapsed time of 25 minutes 59 seconds.
4. St. Louis, Missouri to Cincinnati, Ohio, distance 311.4 miles (501.1 km), average speed 2,189.9 miles per hour (3,524.3 km/h), and an elapsed time of 8 minutes 32 seconds

What is notable here is that these four individual records were set during the same single flight, on March 6th, 1990, by SR-71 serial number 61-7972 in route from Palmdale, California to it's final resting place at the Smithsonian Museum. Following this flight, in recognition of these records and the loss of a valuable national asset, Senator John Glenn gave the following address:

"Mr. President, the termination of the SR-71 was a grave mistake and could place our nation at a serious disadvantage in the event of a future crisis. Yesterday's historic transcontinental flight was a sad memorial to our short-sighted policy in strategic aerial reconnaissance."

Another interesting point to note is that, despite it's one of a kind innovative design, as well as it's mind boggling performance envelope, throughout the Blackbird's entire lifespan from design and development to it's retirement, only 12 planes and one pilot were ever lost. Compared to the safety and service record of almost any other aircraft in existence, this is almost unprecedented.

If you liked this piece, than please check back soon, as here are my planned aircraft to "feature" (so far):

Bell UH-1 "Huey"

Fairchild Republic A-10 Thunderbolt II (better known as the "Warthog")

Lockheed Martin F-22 "Raptor"

Boeing B-17 "Flying Fortress"

Mil Mi-24 "Hind"