SR-71 Blackbird

SR-71A Blackbird

SR-71A Blackbird

The SR-71 was first conceptualized early in 1956, by Kelly Johnson's "Skunk Works" crew at Lockheed. The original design was designated the A-12, a high speed fighter interceptor, and won a highly secret design competition on August 29, 1959 and was finally approved by the CIA under a code-named project Oxcart on January 30, 1960.

The first A-12 to fly was outfitted with two huge J75 engines while Pratt & Whitney Aircraft continued to solve problems with the intended J58 engine. Piloted by Lou Schalk, the A-12 took to the air on April 26, 1962. With the smaller J75s, the aircraft barely surpassed Mach 1, but a barrage of test flights continued anyway. In 1963, the J58s were installed and the ultra high speed features were then able to be added into the test flights.

During the development of the A-12, Kelly Johnson was formulating an idea for a follow on aircraft to the U-2...mainly becuase it was felt that the U.S. would have about three years before the Soviets began to shoot down the U-2. Johnson wanted the follow on aircraft to be designed to use speed as its main protective device. In January of 1961, Kelly Johnson proposed the "Advanced Strategic Reconaissance Aircraft" to the Secretary of the Air Force, Dr. Joseph Charyk. The aircraft was to be designed as a high altitude photographic recon aircraft and despite opposition from those proponents for the XB-70 as the choice for this role, a contract was awarded to Lockheed on December 28, 1962 for the initial six SR-71s.. The aircraft was designed and built by the Advanced Development Project team at the "Skunk Works", the same team which had built the U-2 (also under total secret).

In a rare break from secretive traditions, President Lyndon Baines Johnson announced the "A-11" on February 29, 1964, using photographs of the fighter interceptor prototype version, the YF-12. He then proceeded to describe the reconaissance version as the "SR- 71" instantly changing the already agreed upon "RS-71" designation. The first flight of the SR-71A took place at Plant 42, Palmdale, California, and was flown by Robert J. Gilliland. The first operational flight of the SR-71 was flown on March 21, 1968.

SR-71 Taking off at Beal AFB

SR-71A on display at Military AircraftMuseum

Operations

The 4200th Strategic Reconaissance Wing was activated in 1965, and located at Beale AFB, near Marysville, California. Later this wing was renamed the 9th SRW. In 1976 all SR-71 (and the slower U-2) operations were moved to the 9th SRWat Beale AFB, near Marysville, California, in 1976. Operations continued mainly from Beale until the SR-71's retirement on March 6, 1990. The exceptions were detachments at RAF Mildenhall (Det 4) in the United Kingdom providing SR services to NATO, and Det 1 at Kadena AFB, Japan (Det 1 was phased out in 1989).
The SR-71 mission begins two days before takeoff, and involves precise navigational calculations to ensure that the SR-71 and crew only go exactly where the need to go to get the proper intelligence without any more risk than as necessary and to precisely control the amount of fuel expended. The SR-71, as you might expect is a very thirsty bird, and requires at a minimum two refueling stops per mission.
Prior to the active part of the mission, the crew chief and maintenance crew began preparing the "Blackbirds" for flight. First there are the normal maintenance checks, during which even the smallest problem is fixed. The SR-71 is a very high technology aircraft, so every system is important. Also, the basic cockpit of the SR-71 is pretty standard analog instrumentation, so there are not a lot of redundant sytems for the flight crew to fall back on. It works...or it doesn't.

Then comes the mission preparation steps. This involves purging the fuel system with nitrogen and in many cases pre-heating or pre-cooling the sensor packages.
Also well before the flight is to begin, the KC-135Q tanker crew begins their pre-flight, launches, and heads to their rendevous. All along the intended flight path, KC-135Q tankers may be called upon to be in position, with their launches taking place before the SR-71 takes off. By the time they reach the rendevous, the SR-71 may have flown the length of a continent in the time the tanker has launched and climbed to the rendevous altitude.
The pilots are briefed on the mission prior to suiting up. The crew dons the Dave Clark S1030 pressure suit (similiar to what an astronaut wears) only with the help of the Psychological Support Division (PSD) crew, at a special facility with large recliner chairs built for the crew members. The "Daveys" as the they are called, cost up to $30,000 each. The suit up takes up to 20 minutes, which is followed another 30 minutes reclining in the oversized recliners while breathing pure oxygen. This last step is to purge their bloodstream of any nitrogen, thus avoiding the possibility of the "bends".
While this is going on, the backup crew fully inspects the mission aircraft, which has probably been checked over thoroughly by the crew chief and his crew. The level of maintenance on the SR-71s is extremely professional, and few aircraft problems are found by the inspecting backup crew.
The crew is assisted into the aircraft by the PSD support crew, and the padded covers are removed from around the cockpit area. The "nest" or hanger for each Blackbird contains a completely independent self-start system, which consists of a turbine engine to help turn over the SR-71's J58 engines.
The aircraft's JP-7 fuel has a very high flashpoint, so during the spin-up, the pilot must trigger injection of Triethyl Borane (TEB) into the combustion chambers of the engine. Once the engines are running, all power lines are disconnected and the pilot begins his taxi to the runway. If you were to watch the aircraft carefully at this moment you would see that it is dripping fuel...until the aircraft is at altitude and speed, the airframe is "loose" and fuel leaks prodigiously. Fortunately, the aircraft's JP-7 fuel couldn't be lit with a match.

SR-71A at height over Mountains

SR-71B On Patrol

Before going onto the active taxiway, an engine run-up is performed, and if all is go, then the aircraft is taxied to take-off position. The pilot stands on the brakes (literally, as in all modern aircraft, the brakes are part of the rudder control assembly actuated by the pilot's feet), slowly moves the throttles to full military power (just short of afterburner), and when the RPMs climb to the appropriate number, releases. The aircraft is rolled a few feet, and then the pilot selects afterburner. The awesome 60,000 pounds of thrust creates diamond shaped patterns behind the engine, easily visible during the daylight, and they stretch twenty feet or more from the tail at night. The pilot must retract the landing gear quickly, as the SR-71 will quickly exceed the maximum gear retraction airspeed of 300 knots.
Note that to make a take-off that is safe even with a minor mishap, the SR-71 is lightly fueled on the ground, and only has enough fuel to climb to the first refueling stop above Beale. There the Blackbird "tanks up" filling its wings with the precious fuel, which also serves as part of the thermal control system at high speed.
Since the plan is to refuel immediately, the pilot spares no fuel in making the usual 5,000 foot take-off roll, and climbing to the tanker. Typically, two T-38s monitor the take-off from above and behind, until the SR-71 climbs away.
Refueling is a hairy experience, as the entrance to the fuel vent is behind the pilot and RSO (Reconaissance Systems Officer) . Everyone is very careful, as one SR-71 was lost when the SR-71 rammed the tanker aircraft.
After tanking up, the pilot then climbs to 33,000 feet, noses down a bit to help pass through the sound barrier (occuring around 28,000 feet), then angles back up to climb to the mission altitude (said to be 82,000 to 85,000 feet,although it is generally recognised that the aircraft can operate at much highr altitudes). This maneuver also must be performed carefully, as several "un-starts" or "flame-outs" have occurred as a result of a sudden pitch up maneuver which temporarily blocks the delicate input stream into the engines.
Any number of refueling stops can occur depending on the distance to the target (or more likely the path taken to avoid detection), each requiring de-acceleration and the drop back to refueling altitude.
Using intertial guidance, the pilot flys the plane to the mission area (typically along the target's border...sure I believe that...don't you?), and then the RSO takes over. On autopilot, the aircraft now flys as straight a line as possible to provide the sensors a stable platform. The pilot is constantly fine tuning the aircraft engines as the SR-71 is not fully automatic, and the enviroment at that altitude is not stable for the engines. During high speed runs at altitude, some of the aircraft interior hydraulic systems are heated to 600 degress Fairenheit, and certain portions of the skin reaches temperatures above 1000 degrees. Early A-12 tests had tires explode in flight, despite being shielded inside the wheel wells. At operational throttle settings, the SR-7 burns a prodigious 8000 gallons of fuel per hour.
During the flight, the SR-71 can easily cover 100,000 square miles of territory with its sensors (both electronic and photographic).

Several SR-71s have been lost, with the following list being compiled from a number of sources listed in the MILNET bibliography:

Two lost due to wheel fires (the magnesium wheel, once ignited by heat of a burning tire, put off a great deal of heat!).
One lost due to ramming a tanker aircraft.
In April of 1989 a Beale AFB SR-71 was lost in the South China Sea while on a classified mission.

Before the SR-71s were operational, several A-12s were outfitted with Mach 2 ramjet drones, which were carried piggyback just between the twin stabilizers. One A-12 was lost when a drone's engine failed just after launch, and nosed into the rear canopy, killing the RSO. The drone operations, the A-12 and their missions, and the majority of the SR-71 missions remain classified.
After the mission is complete, the whole cycle repeats itself until the SR-71 begins its final descent into home.
The letdown to landing begins well away from the base, the descent being controlled at 500 fpm to allow the airframe to cool. The landing gear is lowered prior to approach to allow tires to cool before landing, and then may be retracted to improve the stability of the aircraft on final approach. During the approach, excess fuel can be jettisoned to reduce the weight of the aircraft to control the very high sink rate. Control on approach is very heavy, and the pilot must be extremely skillful and the long nose and high angle of attack make an already difficult airplane to land quite a handful. Upon touchdown, the pilot triggers the drag chute to slow the aircraft down to taxi speed.
Once in the hanger, the aircraft is parked, and cooling fans are directed at the aircraft to cool off the still dangerously hot skin. In fact, it is reported that the skin pops and crackles as it cools and contracts. In cases whre the SR-71 has had to land at a base without these facilities, the crew has had to remain inside with the air conditioning of their suits running, while waiting for the skin to cool enough for the recovery crew to help them exit.

SR-71A At Sunset

Summary

It is not clear how the U.S. will fill the void in operational intelligence gathered by the SR- 71 fleet. Perhaps another "black" program is underway or has already delivered a new platform for purposes of Strategic Reconaissance
In "Spy Planes" form Arco Books, Bill Gunston reported that the USAF had contracted Lockheed to work on the "Covert Survivable In-weather Recon/Strike" aircraft (CSIRS). This was in 1983, and Air Force Magazine later reported the program had been cancelled. Perhaps...perhaps not, or perhaps this program led to the F-117A.