SR-71 BLACKBIRD
Flight Journal|September - October 2021
Faster than a speeding bullet!
TED CARLSON

A derivative of the A-12 and YF-12A, which was designed in the late ’50s, the amazing Blackbird remains the fastest ever jet-powered aircraft in the world today. These “speed demons” last belonged to the Air Combat Command’s 9th Reconnaissance Wing at Beale AFB, California, with the last two examples having been based at Edwards AFB, California (Detachment 2, 9th Operations Group). Often referred to as “Det. 2,” they also operated T-38A Talons that were used as companion trainers to keep the pilots and Reconnaissance Systems Officers (RSOs) current. Both the T-38As and the SR-71As had the 9th RW markings and sported the “BB” (Beale’s Best) tail code.

The Habu

The all-weather Blackbird is arguably one of the most famous and high-tech aircraft in the world. The ’60s-vintage, Mach 3+, the titanium-constructed machine continued to soldier on with NASA following Air Force retirement. The official U.S. Air Force name of the classic SR-71 is the Blackbird, but it also is known as “Habu” and “SR.” The SR-71A is on record for having traveled at 2,193 miles per hour at an altitude of over 85,000 feet during a record-breaking flight. This translates into 36 1/2 miles per minute, or over three miles every five seconds. All SR-71s have a crew of two, the pilot and the RSO. It is powered by a pair of Pratt and Whitney JT11D-20B (J58) axial-flow bleed bypass turbojet engines with afterburners, each with 34,000 pounds of thrust. The engines had movable inlet spikes designed to vary the air inlet geometry. The aircraft inlets generated 50% of the engine's thrust by design. In the event of an inlet unstart (50% loss of thrust on a side), an asymmetrical thrust developed, and the aircraft had to be banked 15 degrees into the working engine to counter the situation and break even. The engine inlet system had three redundant computers and moved nearly two feet axially from subsonic to Mach 3 flight.

The Habu range without refueling exceeded 2,500 miles, and maximum endurance with multiple refuelings was crew limited, with 12 hours being the very maximum. For navigation, the SR-71 used a reliable Adaptable Navigation System (ANS), which used star tracking for celestial navigation and had excellent accuracy that was within feet. The Blackbird did not have a GPS, and in the event of a major war, GPS satellites could be threatened but not the stars. The fuselage had a “chine” area that extended to the tip of the forward fuselage to the leading edge of the wings and created an efficient aerodynamic lifting surface. Stealth technology was designed in the form of radar-diffusing iron ball paint, overall shape, and Radar Absorbing Materials (RAM).

Canned heat

The entire airframe, systems, and fluids had to be specially designed to combat excessive heat—a result of its incredibly fast operating speeds. Because of the heat associated with the aircraft speed, the fuel tanks were pressurized with 100-percent inert nitrogen to prevent flash ignition of the fuel. This is why the aircraft was loaded with liquid nitrogen before departure. The liquid nitrogen levels and fuel tank pressure were monitored in the cockpit.

Normal hydraulic fluids lose their properties once heated, so innovative, very high-temperature hydraulic fluids had to be designed for the Blackbird. The engines were designed for continuous operation at compressor inlet temperatures above 400 degrees Centigrade (752 degrees Fahrenheit), a product of high-Mach flight. The jet engine special high-temperature oil had high viscosity at ambient temperatures and had to be heated back to a thinner liquid form prior to engine start. In theory, the titanium construction of the SR-71 became stronger because every time it flew it the metal was heat-treated. The black paint helped dissipate the heat as well.

During a sortie, crew members could heat food by simply placing it against the scorching 550-degree Fahrenheit windshield. During normal high-speed operation, the aircraft's skin temperature ranged from 550 to 900 degrees Fahrenheit, depending on the location. The fuel temperature commonly exceeded 300 degrees Fahrenheit, which was recorded by the mission-recording system. The less fuel that was in the aircraft, the hotter the skin became. The greater the fuel volume, the better the heat sink effect and thus it remained cooler.

The Habu had very high-temperature special tires, made of aluminum impregnated rubber (with a silvery look) and were pressurized with nitrogen at greater than 400 psi. The tires were very stiff due to the composition, and it was difficult to tell if they were even inflated. Although never a requirement, if all the tires were blown, the SR-71 could still taxi. When the gear was retracted, the tires came up into a thermally blanketed area that shielded them from heat.

Well-suited

Both the pilot and RSO had to wear handmade full-pressure suits to survive the hostile high-altitude environment. Two suits, a harness, and a helmet cost approximately $185,000 in 1995 dollars. Each pilot had two of the complex suits, so if a problem with one suit developed just before the sortie, there would be a backup. The suits were pneumatically leak-tested prior to every flight. The suit was a lifesaver in the event of loss of the canopy seal integrity, and if both engines were lost, it would also neutralize pressurization.

In the unfortunate event that a crew may have had to eject, the Blackbird ejection system could work with no airspeed (zero-zero) on the ground and up to Mach 3 and at full altitude. When ejecting at Mach 3, the wind blast is not as significant as one would think because the air is less dense and thinner. An ejection at altitude and at Mach 3 is the equivalent of an ejection from a fighter-type aircraft flying lower at 450 to 500 knots.

During ejection, the pressure suit helped protect the crew, and at altitude, the seat kept the pilots attached by design. A small drogue chute deployed from the seat to slow and stabilize it. This was the way the crew member traveled all the way down to 15,000 feet. Then the seat would automatically throw the pilot out and actuate his parachute. The suit torso harness had a water-activated life preserver built-in, should someone happen to be incapacitated and land in water.

The sensored SR

The main function of the Air Force SR-71As was to carry an array of reliable sensors aloft, at high altitudes, and at blazing speeds. The Air Force SR-71As ended their first flying career in 1990 due to budget cuts. When the program was brought back to life in 1995, the mission and sensors were updated accordingly. The SR-71As were referred to as the old SR and new SR, a product of how much sensors had evolved.

The “old” SR-71A missions (Beale AFB’s 1st SRS) involved mostly flying outside and along (but not over) a border and included a significant amount of wet film (traditional chemical-processed film). The old Blackbird used to be able to be configured with an Electronic Intelligence (ELINT) package, but it wasn’t fielded because of budget constraints, though Congress did mandate its return when the program was revived.

The mission of the “new” SR-71A was high-threat penetration, and Det. 2 stood ready to deploy to forward operating locations and perform overflights if summoned. The new SR-71As had an enhanced Electro-Optical (EO) technology, basically a digital camera system, that was significantly better than it was when the Blackbird was first retired.

One of the primary sensors that the Blackbird carried most the time was a radar sensor, the Advanced Synthetic Aperture Radar System number one (ASARS-1), which was a modular package that was placed in the nose. It allowed a long-range standoff ability and collected reconnaissance information at very good resolution. Inside the cockpit, the RSO had a view of what the ASARS-1 was seeing, which also helped with navigation. In lieu of the ASARS-1, the Optical Bar Camera (OBC) used wet film and could be mounted in the same position. The OBC afforded a panoramic-type view with horizon-to-horizon coverage. When the OBC was used at Mach 3, a 100,000-square-mile per hour could be covered. This capability, termed “synoptic coverage,” was unique to the SR-71.

Another type of camera was Technical Objective Cameras (framing cameras) that were mounted in the chine area along the lower sides of the forward fuselage. The Technical Objective Cameras were being converted from a wet film process to EO with digital imaging. Thus, the images were able to be either data-linked or processed upon return to base. The ASARS-1 could be used in either day or night and in bad weather.

Driving the Habu: a team effort

The elite Habu crews were usually paired together as a team, though on occasion they flew with different crew members. Flying one of the world’s most complex aircraft was a challenging task and one needed to constantly be alert. The conversion course to transition to the SR-71 lasted about nine to 10 months.

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