| SR-71 "Blackbird" | |
|---|---|
| An SR-71B trainer over the Sierra Nevada Mountains of California in 1994. The raised second cockpit is for the instructor. | |
| Role | Strategic reconnaissance aircraft |
| Manufacturer | Lockheed Skunk Works |
| Designer | Clarence "Kelly" Johnson |
| First flight | 22 December 1964 |
| Introduction | 1966 |
| Retired | 1998 |
| Status | Retired |
| Primary users | United States Air Force NASA |
| Number built | 32 |
| Developed from | Lockheed A-12 |
The Lockheed SR-71 "Blackbird" was an advanced, long-range, Mach 3+ strategic reconnaissance aircraft.[1] It was developed as a black project from the Lockheed A-12 reconnaissance aircraft in the 1960s by the Lockheed Skunk Works. Clarence "Kelly" Johnson was responsible for many of the design's innovative concepts. During reconnaissance missions the SR-71 operated at high speeds and altitudes to allow it to outrace threats. If a surface-to-air missile launch was detected, the standard evasive action was simply to accelerate and outrun the missile.[2]
The SR-71 served with the U.S. Air Force from 1964 to 1998. Although 12 of the 32 aircraft built were destroyed in accidents, none was lost to enemy action.[3][4] The SR-71 was unofficially named the Blackbird, and called the Habu by its crews, referring to an Okinawan species of pit viper.[5] Since 1976, it has held the world record for the fastest air-breathing manned aircraft, a record previously held by the YF-12.[6][7][8]
Contents |
Lockheed's previous reconnaissance aircraft was the U-2, which was designed for the Central Intelligence Agency (CIA). In 1960, while overflying the USSR, the U-2 flown by Francis Gary Powers was shot down by Soviet surface-to-air missiles (SAMs). This highlighted the U-2's vulnerability due to its relatively slow speed; this paved the way for the Lockheed A-12, also designed for the CIA by Clarence Johnson at Lockheed's Skunk Works.[9] The A-12 was the precursor of the SR-71. The A-12's first flight took place at Groom Lake (Area 51), Nevada, on 25 April 1962. It was equipped with the less powerful Pratt & Whitney J75 engines due to protracted development of the intended Pratt & Whitney J58. The J58s were retrofitted as they became available, and became the standard powerplant for all subsequent aircraft in the series (A-12, YF-12, M-21) as well as the follow-on SR-71 aircraft.
Thirteen A-12s were built. Two A-12 variants were also developed, including three YF-12A interceptor prototypes, and two M-21 drone carrier variants. The cancellation of A-12 program was announced on 28 December 1966,[10] due to budget concerns,[11] and because of the forthcoming SR-71. The A-12 flew missions over Vietnam and North Korea before its retirement in 1968.
The SR-71 designator is a continuation of the pre-1962 bomber series, which ended with the XB-70 Valkyrie. During the later period of its testing, the B-70 was proposed for a reconnaissance/strike role, with an RS-70 designation. When it was clear that the A-12 performance potential was much greater, the Air Force ordered a variant of the A-12 in December 1962.[12] Originally named R-12[N 1] by Lockheed, the Air Force version was longer and heavier than the A-12, with a longer fuselage to hold more fuel, two seats in the cockpit, and reshaped chines. Reconnaissance equipment included signals intelligence sensors, a side-looking radar and a photo camera.[12] The CIA's A-12 was a better photo reconnaissance platform than the Air Force's R-12, since the A-12 flew somewhat higher and faster,[11] and with only one pilot it had room to carry a superior camera[11] and more instruments.[13]
During the 1964 campaign, Republican presidential nominee Barry Goldwater repeatedly criticized President Lyndon B. Johnson and his administration for falling behind the Soviet Union in developing new weapons. Johnson decided to counter this criticism by revealing the existence of the YF-12A Air Force interceptor, which also served as cover for the still-secret A-12,[14] and the Air Force reconnaissance model since July 1964. Air Force Chief of Staff General Curtis LeMay preferred the SR (Strategic Reconnaissance) designation and wanted the RS-71 to be named SR-71. Before the July speech, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the story that the president had misread the aircraft's designation.[15][16]
This public disclosure of the program and its renaming came as a shock to everyone at the Skunk Works and to Air Force personnel involved in the program. All of the printed maintenance manuals, flight crew handbooks,[N 2] training slides and materials were labeled "R-12"; also Certificates of Completion issued by the Skunk Works to the first Air Force Flight Crews and their Wing Commander were labeled "R-12 Flight Crew Systems Indoctrination, Course VIII". The name change was taken as an order from the Commander-in-Chief, and immediate reprinting began on materials, including 29,000 blueprints, with the new name.
A particularly difficult issue with flight at over Mach 3 is the high temperatures generated. As an aircraft moves through the air at supersonic speed, the air in front of the aircraft is compressed into a supersonic shock wave, and the energy generated by this heats the airframe. To address this problem, high-temperature materials were needed, and the airframe of the SR-71 was substantially made of titanium, obtained from the USSR at the height of the Cold War. Lockheed used many guises to prevent the Soviet government from knowing what the titanium was to be used for. In order to control costs, Lockheed used a more easily worked alloy of titanium which softened at a lower temperature. Finished aircraft were painted a dark blue, almost black, to increase the emission of internal heat (fuel acted as a heat sink for avionics cooling) and to act as camouflage against the night sky. The aircraft was designed to minimize its radar cross-section, an early attempt at stealth design.[17] The aircraft's call sign was "Blackbird", because of its dark color.
The air inlets allowed the plane to cruise at over Mach 3.2, yet kept air flowing into the turbojet engines at a subsonic, Mach 0.5 speed. At the front of each inlet was a sharply pointed movable cone called a "spike" that was locked in its full forward position on the ground and when in subsonic flight. As the aircraft accelerated past Mach 1.6, an internal jackscrew moved the spike as much as 26 inches (66 cm) to the rear.[18]
The original air inlet computer was an analog design which, based on pitot-static, pitch, roll, yaw, and angle-of-attack inputs, would determine how much movement was required. By moving, the spike tip would withdraw the shock wave, riding on it closer to the inlet cowling until it just touched slightly inside the cowling lip. In this position shock-wave spillage, causing turbulence over the outer nacelle and wing, was minimized while the spike shock-wave then repeatedly reflected between the spike centerbody and the inlet inner cowl sides. In doing so, shock pressures were maintained while slowing the air until a Mach 1 shock wave formed in front of the engine compressor.[19]
The backside of this "normal" shock wave was subsonic air for ingestion into the engine compressor. This capture of the Mach 1 shock wave within the inlet was called "Starting the Inlet". Tremendous pressures would be built up inside the inlet and in front of the compressor face. Bleed tubes and bypass doors were designed into the inlet and engine nacelles to handle some of this pressure and to position the final shock to allow the inlet to remain "started". Air that is compressed by the inlet/shockwave interaction is diverted around the turbo machinery of the engine and directly into the afterburner where it is mixed and burned. This configuration is essentially a ramjet and provides up to 70% of the aircraft's thrust at higher mach numbers.
Ben Rich, the Lockheed Skunkworks designer of the inlets, often referred to the engine compressors as "pumps to keep the inlets alive" and sized the inlets for Mach 3.2 cruise (where the aircraft was at its most efficient design point).[20] The additional "thrust" refers to the reduction of engine energy required to compress the airflow. One unique characteristic of the SR-71 is that the faster it went, the more fuel-efficient it was in terms of pounds burned per nautical mile traveled. An incident related by Brian Shul, author of Sled Driver: Flying the World's Fastest Jet, was that on one reconnaissance run he was fired upon several times. In accordance with procedure they accelerated and maintained the higher than normal velocity for some time; afterwards they discovered that this had reduced their fuel consumption.[21]
In the early years of the Blackbird programs the analog air inlet computers would not always keep up with rapidly changing flight environmental inputs. If internal pressures became too great and the spike was incorrectly positioned the shock wave would suddenly blow out the front of the inlet, called an "Inlet Unstart." The flow of air through the engine compressor would immediately stop, thrust would drop, and exhaust gas temperatures would begin to rise. Due to the tremendous thrust of the remaining engine pushing the aircraft asymmetrically an unstart would cause the aircraft to yaw violently to one side. SAS, autopilot, and manual control inputs would fight the yawing, but often the extreme off-angle would reduce airflow in the opposite engine and cause it to begin "sympathetic stalls". The result would be rapid counter-yawing, often loud "banging" noises and a rough ride. The crews' pressure-suit helmets would sometimes bang on the cockpit canopies until the initial unstart motions subsided.[22]
One of the standard counters to an inlet unstart was for the pilot to unstart both inlets. This stopped the aircraft's yawing and pitching, and allowed the pilot to restart the inlets.[23] Lockheed implemented an electronic control to detect unstart conditions and perform this action without pilot intervention.[24] The initial analog inlet control system was replaced by a digital system beginning in 1980. The new system prevented many of the unstarts encountered during flights.[25]
Before the Blackbird, titanium was used only in high-temperature exhaust fairings and other small parts directly related to supporting, cooling, or shaping high-temperature areas on aircraft. However, up to 85% of the Blackbird's structure consisted of titanium, with the remaining 15% in composite materials. Such extensive use of these materials in aircraft construction was a first in the industry. The advances made by Lockheed in fabrication have been used subsequently throughout the industry in the design and production of high-speed aircraft, including most modern fighter types.
Titanium was difficult to work with, expensive, and scarce. Initially, 80% of the titanium delivered to Lockheed was rejected due to metallurgical contamination.[26][27] One of the difficulties found was that welds made during the summer were corroding and degrading the titanium due to higher levels of chlorine in the local water supply during that season. The problem was solved by changing to using distilled water as welding coolant. Cadmium plated tools were also found to cause corrosion, and had to be replaced.[28] Studies of the aircraft's titanium skin revealed that the metal was actually growing stronger over time, because of intense heating due to compression of the air, caused by the rapid flight of the vehicle, i.e. heat treatment.
Major portions of the upper and lower inboard wing skin of the SR-71 were corrugated, not smooth. The thermal expansion stresses of a smooth skin would have caused splitting or curling. By making the surface corrugated, the skin was allowed to expand vertically and horizontally without overstressing, which also increased longitudinal strength. Despite its success, aerodynamicists initially opposed the concept and accused the design engineers of trying to make a 1920s era Ford Trimotor — known for its corrugated aluminum skin — go Mach 3.[20] The red stripes on some SR-71s are to prevent maintenance workers damaging the skin. The curved skin near the center of the fuselage is thin and delicate. There is no support underneath with exception of the structural ribs, which are spaced several feet apart.
To allow for thermal expansion at the high operational temperatures, the fuselage panels were manufactured to fit only loosely on the ground. Proper alignment was only achieved when the airframe heated due to air resistance at high speeds, causing the airframe to expand several inches. Because of this, and the lack of a fuel sealing system that could handle the thermal expansion of the airframe at extreme temperatures, the aircraft would leak JP-7 jet fuel onto the runway before it took off. The aircraft would quickly make a short sprint, meant to warm up the airframe, and was then refueled in the air before departing on its mission. Cooling was carried out by cycling fuel behind the titanium surfaces at the front of the wings (chines). On landing after a mission the canopy temperature was over 300 °C (572 °F), too hot to approach. Non-fibrous asbestos with high heat tolerance was used in high-temperature areas.[20]
The SR-71 was the first operational aircraft designed around a stealthy shape and materials. There were a number of features in the SR-71 that were designed to reduce its radar signature. The first studies in radar stealth technology seemed to indicate that a shape with flattened, tapering sides would avoid reflecting most radar energy toward the radar beams' place of origin. To this end, the radar engineers suggested adding chines to the design and canting the vertical control surfaces inward. The aircraft also used special radar-absorbing materials which were incorporated into sawtooth shaped sections of the skin of the aircraft, as well as cesium-based fuel additives to reduce the exhaust plumes' visibility on radar. Despite these efforts, the SR-71 was still easily detected on radar while traveling at speed due to its large exhaust stream and air heated by the body (large thermal gradients in the atmosphere are detectable with radar). The SR-71's radar cross section (RCS) of almost 10 square meters[29] was much greater than the later F-117's RCS, which is similar to that of a small ball bearing.[30]
The overall effectiveness of these designs is still debated; Ben Rich's team could show that the radar return was, in fact, reduced, but Kelly Johnson later conceded that Russian radar technology was advancing faster than the "anti-radar" technology Lockheed was using to counter it.[31] The SR-71 made its debut years before Pyotr Ya. Ufimtsev's ground-breaking research made possible today's stealth technologies, and, despite Lockheed's best efforts, the SR-71 was still easy to track by radar and had a huge infrared signature when cruising at Mach 3.2 or more. It was visible on radar since air traffic control was able to track it even when not using its transponder,[32] and missiles were often fired at the aircraft.
Although equipped with defensive electronic countermeasures, the SR-71's greatest protection was its high top speed, which made it almost invulnerable to the attack technologies of the time. Over the course of its service life, no SR-71 was shot down, despite many attempts to do so. It flew too fast and too high for surface-to-air missile systems to track and shoot down, and was much faster than the Soviet Union's fastest aircraft of the time, the MiG-25: although the MiG had a top speed of Mach 3.2 at high altitude, the engines would burn up at that speed.[33] If a surface-to-air missile was fired at an SR-71, the pilot could accelerate to avoid it.[2]
One of the Blackbird's interesting features was its chines, sharp edges leading aft on either side of the nose and along the sides of the fuselage.
The Blackbird was originally not going to have chines. At its A-3 design stage, the fuselage had a circular or vertical oval cross section. Dr. Frank Rodgers, of the Scientific Engineering Institute (a CIA front company), had discovered that a section of a sphere—round on the bottom and flat on top—had a greatly reduced radar reflection. He adapted this to a cylindrical fuselage by 'stretching' the sides out and leaving the bottom round.[34] After the advisory panel provisionally selected Convair's FISH design over the A-3 on the basis of RCS, Lockheed adopted chines for its A-4 through A-6 designs,[35] and used them in redesigning the A-11 into the A-12.
The aerodynamicists discovered that the chines generated powerful vortices around themselves, generating much additional lift near the front of the aircraft, leading to surprising improvements in aerodynamic performance.[36] The angle of incidence of the delta wings could then be reduced, allowing for greater stability and less high-speed drag, and more weight (fuel) could be carried, allowing for greater range. Landing speeds were also reduced, since the chines' vortices created turbulent flow over the wings at high angles of attack, making it harder for the wings to stall. The Blackbird can, consequently, make high-alpha turns to the point where the Blackbird's unique engine air inlets stop ingesting enough air, which can cause the engines to flame out.[37] Blackbird pilots were thus warned not to pull more than 3 g, so that angles of attack stay low enough for the engines to get enough air. The chines act like the leading edge extensions that increase the agility of modern fighters such as the F-5, F-16, F/A-18, MiG-29 and Su-27. The addition of chines also allowed designers to drop the planned canard foreplanes. Early design models of what became the Blackbird featured canards.[N 3][38][39]
When the Blackbird was being designed, no other airplane had featured chines, so Lockheed's engineers had to solve problems related to the differences in stability and balance caused by these unusual surfaces. Their solutions have since been extensively used. Chines remain an important design feature of many of the newest stealth UAVs, such as the Dark Star, Bird of Prey, X-45 and X-47, since they allow for tail-less stability as well as for stealth.
Several exotic fuels were investigated for the Blackbird. Development began on a coal slurry powerplant, but Johnson determined that the coal particles damaged engine components.[20] He then began researching a liquid hydrogen powerplant, but the tanks required to store cryogenic hydrogen did not suit the Blackbird's size and shape.[20]
Ultimately, the Blackbird would burn JP-7 jet fuel, a somewhat more conventional hydrocarbon, yet still unusual in that it is not a distillate fuel but is created from special blending stocks. It is a mixture composed primarily of hydrocarbons, including alkanes, cycloalkanes, alkylbenzenes, indanes/tetralins, and naphthalenes, with addition of fluorocarbons to increase its lubricity, an oxidizing agent to enable it to burn in the engines, and a cesium compound, A-50, to disguise the exhaust's radar signature.
JP-7 is very slippery, a disadvantage on the ground, because the aircraft leaked small amounts of fuel when not flying. But it had a relatively high flash point (140 °F, 60 °C), which decreased the fire hazard and allowed it to be used as a coolant and hydraulic fluid in the aircraft before being burned. Indeed, JP-7 was extremely difficult to light in any conventional way. To start the engines, puffs of triethylborane (TEB), which ignites on contact with air, were injected to produce temperatures high enough to ignite the JP-7. The TEB produced a characteristic puff of greenish flame that could often be seen as the engines were ignited.[21] TEB was also used to ignite the afterburners. The aircraft carried 20 fluid ounces (600 ml) of TEB per engine, enough for at least 16 injections, more than enough for any missions it was likely to carry out. A counter told the pilot how many TEB injections remained.
Crews flying the SR-71 at 80,000 ft (24,000 m) faced two main survival problems: maintaining consciousness at high altitude, and surviving ejection. With a standard pressure demand oxygen mask, human lungs cannot absorb oxygen quickly enough above 43,000 ft (13,000 m). The pressure difference inside the mask versus the cockpit pressure on the chest also makes exhalation extremely difficult. In addition, emergency ejection at Mach 3.2 would expose the pilot to an instant heat rise pulse of approximately 450 °F (230 °C) as a result of the air flow. To solve these problems, the David Clark Company was hired to produce protective full pressure suits for the A-12, YF-12, MD-21 and SR-71 aircraft. These suits were later adapted for use on the Space Shuttle.
In addition, cruising at Mach 3.2 would heat the aircraft's external surface well above 500 °F (260 °C)[40] and the inside of the windshield to 250 °F (120 °C), so a robust coolant system was vital. This was achieved with an air conditioner, which used a heat exchanger to dump heat from the cockpit into the fuel prior to combustion.
After a high altitude bailout, an onboard oxygen supply would keep the suit pressurized. The crew member would then free-fall to 15,000 ft (4,600 m) before the main parachute was opened, allowing heat to bleed off. To demonstrate this full pressure suit capability, crew members would wear one of these suits and undergo an altitude chamber explosive decompression at 78,000 ft (24,000 m) or higher while chamber heaters would be turned on to 450 °F (230 °C), gradually decreasing at the expected rate in real life free-fall.
The cabin could be pressurized to an altitude of 10,000 ft (3,000 m) or 26,000 ft (7,900 m) during flight.[41] So, crews flying a low-subsonic flight (such as a ferry mission) would wear either standard USAF hard hat helmets, pressure demand oxygen masks and nomex flying suits, or a full pressure suit.
The Blackbird's Pratt & Whitney J58-P4 engines were innovative marvels that used the most extreme materials of their time. Each J58 could produce 32,500 lbf (145 kN) of static thrust.[42] The only American engines designed to operate continuously on afterburner, the J58 engines were most efficient around Mach 3.2,[43][44] and this was the Blackbird's typical cruising speed.
A unique hybrid, the engine can be thought of as a turbojet inside a ramjet. At lower speeds, the turbojet provided most of the compression and most of the energy from fuel combustion. At higher speeds, the turbojet largely ceased to provide thrust; instead, air was compressed by the shock cones and fuel burned in the afterburner.
In detail, air was initially compressed (and thus also heated) by the shock cones, which generated shock waves that slowed the air down to subsonic speeds relative to the engine. The air then passed through four compressor stages and was split by movable vanes: some of the air entered the compressor fans ("core-flow" air), while the rest of the air went straight to the afterburner (via six bypass tubes). The air traveling through the turbojet was further compressed (and further heated), and then fuel was added to it in the combustion chamber: it then reached the maximum temperature anywhere in the Blackbird, just low enough to keep the turbine blades from softening. After passing through the turbine (and thus being cooled somewhat), the core-flow air went through the afterburner and met with any bypass air.
Around Mach 3, the increased heating from the shock cone compression, plus the heating from the compressor fans, was enough to get the core air to high temperatures, and little fuel could be added in the combustion chamber without melting the turbine blades. This meant the whole compressor-combustor-turbine set-up in the core of the engine provided less power, and the Blackbird flew predominantly on air bypassed straight to the afterburners, forming a large ramjet effect.[20][45][46]The maximum speed was limited by the specific maximum temperature for the compressor inlet of 800 °F (427 °C).
Early 1990s studies of inlets of this type indicated that newer technology could allow for inlet speeds with a lower limit of Mach 6.[47]
Originally, the Blackbird's engines started up with the assistance of an external engine referred to as a "start cart". The cart included two Buick Wildcat V8 engines positioned underneath the aircraft. The two engines powered a single, vertical driveshaft connecting to a single J58 engine. Once one engine was started, the cart was wheeled to the other side of the aircraft to start the other engine. The operation was deafening. Later, big-block Chevrolet engines were used. Eventually, a quieter, pneumatic start system was developed for use at Blackbird main operating bases, but the start carts remained to support recovery team Blackbird starts at diversion landing sites not equipped to start J-58 engines.[48]
Developed years before the Global Positioning System (GPS) simplified navigation, the Blackbird required unprecedented precision for route accuracy, sensor pointing and target tracking. Inertial navigation systems had been developed for the U-2 and A-12, but U.S. Air Force planners wanted a system that would limit inertial position error growth for the longer missions envisioned for the R-12 / SR-71.
The solution was to create an astro-inertial navigation system (ANS) that could correct inertial orientation errors with celestial observations. Nortronics, Northrop's electronics development organization, had in the mid-1950s developed an ANS for the Air Force's SM-62 Snark missile, and a few years later, one for the AGM-48 Skybolt missile. After the Skybolt was cancelled in December 1962, Nortronics began adapting its work for the Blackbird program. A Nortronics "Skunkworks" type organization in Hawthorne, California, completed the development of this system, sometimes referred to as the NAS-14 or NAS-21.
The ANS sat behind the Reconnaissance Systems Officer (RSO) station and tracked stars through a round quartz window in the upper fuselage.[21] Keeping the system cool while cruising at Mach 3.2+ was a tough problem solved by Lockheed and Nortronics engineers during the early test phases.
A time-consuming primary alignment was done on the ground to bring the inertial components to a high degree of accuracy for the start of a mission. Once in flight, a "blue light" source star tracker, which could detect and find stars during day or night, would continuously track a variety of stars as the changing aircraft position brought them into view. The system's digital computer ephemeris contained data on 56 (later 61) stars.[49] The ANS was later modified to speed up the ground alignment and even start it in the air.
The ANS could supply attitude and position inputs to flight controls and other systems, including the Mission Data Recorder, Auto-Nav steering to preset destination points, automatic pointing and control of cameras at control points and optical or SLR sighting of fix points contained on tape loaded into the ANS before takeoff.[50]
The SR-71 originally included optical/infrared imagery systems; side-looking airborne radar (SLAR); electronic intelligence (ELINT) gathering systems; defensive systems for countering missile and airborne fighters; and recorders for SLAR, ELINT and maintenance data.
Imagery systems used on the Blackbird were diverse. At the simple end of the spectrum, the SR-71 carried a Fairchild tracking camera of modest resolution and an HRB Singer infrared camera, both of which ran during the entire mission to document where the aircraft flew and answer any post-flight political charges of overflight. The infrared camera was not used in the later years of the SR-71 operation.
Because the SR-71 carried an observer behind the pilot, it could not use the A-12's principal sensor, a single large-focal-length optical camera that sat in the "Q-Bay" behind the cockpit. Instead, the Blackbird required camera systems that could be located in the wing chines or in the interchangeable nose of the aircraft. Wide-area imaging was provided by two of Itek's Operational Objective Cameras (OOCs), which provided stereo imagery left and right of the flight track, or an Itek Optical Bar Camera (OBC), which, carried in the nose in place of the SLR, gave continuous horizon-to horizon coverage. A closer view of the target area was given by the HYCON Technical Objective Camera (TEOC), that could look up to 45 degrees left or right of centerline.[51] SR-71s carried two of them, each with a six-inch (152 mm) resolution, enough to show the painted lines in parking lots from 83,000 feet (25,000 m). Initially, the TEOCs could not match the resolution of the A-12's larger camera, but improvements in the camera and film within a few years improved their performance greatly.[51][52]
Side-looking radar, built by Goodyear Aerospace in Arizona, was carried in the removable nose section (which could be loaded with the SLR antenna in the maintenance shop before installation on the Blackbird). It was eventually replaced by Loral's Advanced Synthetic Aperture Radar System (ASARS-1) and built and supported by Goodyear. Both the first SLR and ASARS-1 were ground mapping imaging systems and could collect data in fixed swaths left or right of centerline or from a spot location where higher resolution was desired.[51] ASARS-1 could, for example, look through the open door of an aircraft hangar.
ELINT-gathering systems, called the Electro Magnetic Reconnaissance System (EMR), built by AIL could be carried in the left and right chine bays to provide a wide view of the electronic signal fields the Blackbird was flying through.[51][53] Computer-loaded instructions looked for items of special intelligence interest.
Over its operational life, the Blackbird carried various electronic countermeasures, including warning and active electronic systems built by several ECM companies and called Systems A, A2, A2C, B, C, C2, E, G, H and M. On a given mission, an aircraft would carry several of these frequency/purpose payloads to meet the expected threats.
Recording systems captured SLR phase shift history data for ground correlation after landing, ELINT-gathered data, and Maintenance Data Recorder (MDR) information for post-flight ground analysis of the aircraft and its systems' overall health. From an altitude of 80,000 feet (24,000 m), it could survey 100,000 square miles (260,000 km2) per hour of the Earth's surface.[54]
In the later years of its operational life, a data-link system could send ASARS-1 and ELINT data from about 2,000 nmi (3,700 km) of track coverage to a suitably equipped ground station.
The first flight of an SR-71 took place on 22 December 1964, at Air Force Plant 42 in Palmdale, California.[55] The first SR-71 to enter service was delivered to the 4200th (later, 9th) Strategic Reconnaissance Wing at Beale Air Force Base, California, in January 1966.[56] The United States Air Force Strategic Air Command had SR-71 Blackbirds in service from 1966 through 1991.
SR-71s first arrived at the 9th SRW's Operating Location (OL-8) at Kadena Air Base, Okinawa on 8 March 1968.[57] These deployments were code named "Glowing Heat", while the program as a whole was code named "Senior Crown". Reconnaissance missions over North Vietnam were code named "Giant Scale".
On 21 March 1968, Major (later General) Jerome F. O'Malley and Major Edward D. Payne flew the first operational SR-71 sortie in SR-71 serial number 61-7976 from Kadena AB, Okinawa.[57] During its career, this aircraft (976) accumulated 2,981 flying hours and flew 942 total sorties (more than any other SR-71), including 257 operational missions, from Beale AFB; Palmdale, California; Kadena Air Base, Okinawa, Japan; and RAF Mildenhall, England. The aircraft was flown to the National Museum of the United States Air Force near Dayton, Ohio in March 1990.
From the beginning of the Blackbird's reconnaissance missions over enemy territory (North Vietnam, Laos, etc.) in 1968, the SR-71s averaged approximately one sortie a week for nearly two years. By 1970, the SR-71s were averaging two sorties per week, and by 1972, they were flying nearly one sortie every day.
While deployed in Okinawa, the SR-71s and their aircrew members gained the nickname Habu (as did the A-12s preceding them) after a pit viper indigenous to Japan, which the Okinawans thought the plane resembled.[5]
Swedish JA 37 Viggen fighter pilots, using the predictable patterns of SR-71 routine flights over the Baltic Sea, managed to lock their radar on the SR-71 on numerous occasions. Despite heavy jamming from the SR-71, target illumination was maintained by feeding target location from ground-based radars to the fire-control computer in the Viggen.[58] The most common site for the lock-on to occur was the thin stretch of international airspace between Öland and Gotland that the SR-71 used on the return flight.[59][60][61]
Operational highlights for the entire Blackbird family (YF-12, A-12, and SR-71) as of about 1990 included:[62]
Only one crew member, Jim Zwayer, a Lockheed flight-test reconnaissance and navigation systems specialist, was killed in a flight accident. The rest of the crew members ejected safely or evacuated their aircraft on the ground.
The highly specialized tooling used in manufacturing the SR-71 was ordered to be destroyed in 1968 by then-Secretary of Defense Robert McNamara, per contractual obligations at the end of production. Destroying the tooling killed any chance of there being an F-12B, but also limited the SR-71 force to the 32 completed, the final SR-71 order having to be cancelled when the tooling was destroyed.
In the 1970s, the SR-71 was placed under closer congressional scrutiny and, with budget concerns, the program was soon under attack. Both Congress and the USAF sought to focus on newer projects like the B-1 Lancer and upgrades to the B-52 Stratofortress, whose replacement was being developed. While the development and construction of reconnaissance satellites was costly, their upkeep was less than that of the nine SR-71s then in service.
The SR-71 had never gathered significant supporters within the Air Force, making it an easy target for cost-conscious politicians. Also, parts were no longer being manufactured for the aircraft, so other airframes had to be cannibalized to keep the fleet airworthy. The aircraft's lack of a datalink (unlike the Lockheed U-2) meant that imagery and radar data could not be used in real time, but had to wait until the aircraft returned to base. The Air Force saw the SR-71 as a bargaining chip which could be sacrificed to ensure the survival of other priorities. A general misunderstanding of the nature of aerial reconnaissance and a lack of knowledge about the SR-71 in particular (due to its secretive development and usage) was used by detractors to discredit the aircraft, with the assurance given that a replacement was under development. In 1988, Congress was convinced to allocate $160,000 to keep six SR-71s (along with a trainer model) in flyable storage that would allow the fleet to become airborne within 60 days. The USAF refused to spend the money. While the SR-71 survived attempts to be retired in 1988, partly due to the unmatched ability to provide high quality coverage of the Kola Peninsula for the US Navy,[63] the decision to retire the SR-71 from active duty came in 1989, with the SR-71 flying its last missions in October that year.[64]
Funds were redirected to the financially troubled B-1 Lancer and B-2 Spirit programs. Four months after the plane's retirement, General Norman Schwarzkopf, Jr., was told that the expedited reconnaissance which the SR-71 could have provided was unavailable during Operation Desert Storm.[65] However, it was noted by SR-71 supporters that the SR-71B trainer was just coming out of overhaul and that one SR-71 could have been made available in a few weeks, and a second one within two months. Since the aircraft was recently retired, the support infrastructure was in place and qualified crews available. The decision was made by Washington not to bring the aircraft back.
Due to increasing unease about political conditions in the Middle East and North Korea, the U.S. Congress re-examined the SR-71 beginning in 1993.[65] At a hearing of the Senate Committee on Armed Services, Senator J. James Exon asked Admiral Richard C. Macke:
| “ | If we have the satellite intelligence that you collectively would like us to have, would that type of system eliminate the need for an SR-71… Or even if we had this blanket up there that you would like in satellites, do we still need an SR-71? | ” |
Macke replied,
| “ | From the operator's perspective, what I need is something that will not give me just a spot in time but will give me a track of what is happening. When we are trying to find out if the Serbs are taking arms, moving tanks or artillery into Bosnia, we can get a picture of them stacked up on the Serbian side of the bridge. We do not know whether they then went on to move across that bridge. We need the [data] that a tactical, an SR-71, a U-2, or an unmanned vehicle of some sort, will give us, in addition to, not in replacement of, the ability of the satellites to go around and check not only that spot but a lot of other spots around the world for us. It is the integration of strategic and tactical."[66] | ” |
Rear Admiral Thomas F. Hall addressed the question of why the SR-71 was retired, saying it was under "the belief that, given the time delay associated with mounting a mission, conducting a reconnaissance, retrieving the data, processing it, and getting it out to a field commander, that you had a problem in timeliness that was not going to meet the tactical requirements on the modern battlefield. And the determination was that if one could take advantage of technology and develop a system that could get that data back real time… that would be able to meet the unique requirements of the tactical commander." Hall stated that "the Advanced Airborne Reconnaissance System, which was going to be an unmanned UAV" would meet the requirements but was not affordable at the time. He said that they were "looking at alternative means of doing [the job of the SR-71]."[66]
Macke told the committee that they were "flying U-2s, RC-135s, [and] other strategic and tactical assets" to collect information in some areas.[66]
Senator Robert Byrd and other Senators complained that the "better than" successor to the SR-71 had yet to be developed at the cost of the "good enough" serviceable aircraft. They maintained that, in a time of constrained military budgets, designing, building, and testing an aircraft with the same capabilities as the SR-71 would be impossible.[62]
Congress' disappointment with the lack of a suitable replacement for the Blackbird was cited concerning whether to continue funding imaging sensors on the U-2. Congressional conferees stated the "experience with the SR-71 serves as a reminder of the pitfalls of failing to keep existing systems up-to-date and capable in the hope of acquiring other capabilities."[62]
It was agreed to add $100 million to the budget to return three SR-71s to service, but it was emphasized that this "would not prejudice support for long-endurance UAVs [such as the Global Hawk]." The funding was later cut to $72.5 million.[62] The Skunk Works was able to return the aircraft to service under budget, coming in at $72 million.[67]
Colonel Jay Murphy (USAF Retired) was made the Program Manager for Lockheed's reactivation plans. Retired Air Force Colonels Don Emmons and Barry MacKean were put under government contract to remake the plane's logistic and support structure. Still-active Air Force pilots and Reconnaissance Systems Officers (RSOs) who had worked with the aircraft were asked to volunteer to fly the reactivated planes. The aircraft was under the command and control of the 9th Reconnaissance Wing at Beale Air Force Base and flew out of a renovated hangar at Edwards Air Force Base. Modifications were made to provide a data-link with "near real-time" transmission of the Advanced Synthetic Aperture Radar's imagery to sites on the ground.[62]
The reactivation met much resistance: the Air Force had not budgeted for the aircraft, and UAV developers worried that their programs would suffer if money was shifted to support the SR-71s. Also, with the allocation requiring yearly reaffirmation by Congress, long-term planning for the SR-71 was difficult.[62] In 1996, the Air Force claimed that specific funding had not been authorized, and moved to ground the program. Congress reauthorized the funds, but, in October 1997, President Bill Clinton used the line-item veto to cancel the $39 million allocated for the SR-71. In June 1998, the Supreme Court of the United States ruled that the line-item veto was unconstitutional. All this left the SR-71's status uncertain until September 1998, when the Air Force called for the funds to be redistributed. The plane was permanently retired in 1998. The Air Force quickly disposed of their SR-71s, leaving NASA with the two last flyable Blackbirds until 1999.[68] All other Blackbirds have been moved to museums except for the two SR-71s and a few D-21 drones retained by the NASA Dryden Flight Research Center.[67]
Important dates pulled from many sources.[69]
The SR-71 was the world's fastest and highest-flying operational manned aircraft throughout its career. On 28 July 1976, SR-71 serial number 61-7962 broke the world record for its class: an "absolute altitude record" of 85,069 feet (25,929 m).[8][71][72][73] Several aircraft exceeded this altitude in zoom climbs but not in sustained flight.[8] That same day SR-71, serial number 61-7958 set an absolute speed record of 1,905.81 knots (2,193.2 mph; 3,529.6 km/h).[8][73]
The SR-71 also holds the "Speed Over a Recognized Course" record for flying from New York to London distance 3,508 miles (5,646 km), 1,435.587 miles per hour (2,310.353 km/h), and an elapsed time of 1 hour 54 minutes and 56.4 seconds, set on 1 September 1974 while flown by U.S. Air Force Pilot Maj. James V. Sullivan and Maj. Noel F. Widdifield, reconnaissance systems officer (RSO).[74] This equates to an average velocity of about Mach 2.68, including deceleration for in-flight refueling. Peak speeds during this flight were probably closer to the declassified top speed of Mach 3.2+. For comparison, the best commercial Concorde flight time was 2 hours 52 minutes, and the Boeing 747 averages 6 hours 15 minutes.
On 26 April 1971, 61-7968 flown by Majors Thomas B. Estes and Dewain C. Vick flew over 15,000 miles (24,000 km) in 10 hrs. 30 min. This flight was awarded the 1971 Mackay Trophy for the "most meritorious flight of the year" and the 1972 Harmon Trophy for "most outstanding international achievement in the art/science of aeronautics".[75]
When the SR-71 was retired in 1990, one Blackbird was flown from its birthplace at United States Air Force Plant 42 in Palmdale, California, to go on exhibit at what is now the Smithsonian Institution's Steven F. Udvar-Hazy Center in Chantilly, Virginia. On 6 March 1990, Lt. Col. Raymond "Ed" E. Yielding and Lt. Col. Joseph "Jt" T. Vida piloted SR-71 S/N 61-7972 on its final Senior Crown flight and set four new speed records in the process.
These four speed records were accepted by the National Aeronautic Association (NAA), the recognized body for aviation records in the United States.[76] After the Los Angeles–Washington flight, Senator John Glenn addressed the United States Senate, chastening the Department of Defense for not using the SR-71 to its full potential:
| “ | 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. | ” |
|
—Senator John Glenn, 7 March 1990[77] |
||
Much speculation exists regarding a replacement for the SR-71, most notably aircraft identified as the Aurora. This is due to limitations of spy satellites, which are governed by the laws of orbital mechanics. It may take up to 24 hours before a satellite is in proper orbit to photograph a particular target, far longer than a reconnaissance plane. Spy planes can provide the most current intelligence information and collect it when lighting conditions are optimum. The fly-over orbit of spy satellites may also be predicted and can allow the enemy to hide assets when they know the satellite is above, a drawback spy planes lack. These factors have led many to doubt that the US has abandoned the concept of spy planes to complement reconnaissance satellites.[78] Unmanned aerial vehicles (UAVs) are also used for much aerial reconnaissance in the 2000s. They have the advantage of being able to overfly hostile territory without putting human pilots at risk.
Production of the SR-71 totaled 32 aircraft with 29 SR-71As, 2 SR-71Bs, and the single SR-71C.[82]
Data from SR-71.org,[83] Pace[84]
General characteristics
Performance
In total, 32 SR-71s were built. Twelve SR-71s were lost and one pilot died in accidents during the aircraft's service career.[3][4] Eleven of these accidents happened between 1966 and 1972.
| Serial number | Model | Location or fate |
|---|---|---|
| 61-7950 | SR-71A | Lost, 10 January 1967 |
| 61-7951 | SR-71A | Pima Air & Space Museum, Tucson, Arizona |
| 61-7952 | SR-71A | Lost, 25 January 1966 |
| 61-7953 | SR-71A | Lost, 18 December 1969[87] |
| 61-7954 | SR-71A | Lost, 11 April 1969 |
| 61-7955 | SR-71A | Air Force Flight Test Center Museum, Edwards Air Force Base, California[88] |
| 61-7956 | SR-71B | Air Zoo, Kalamazoo, Michigan |
| 61-7957 | SR-71B | Lost, 11 January 1968 |
| 61-7958 | SR-71A | Museum of Aviation, Warner Robins, Georgia |
| 61-7959 | SR-71A | Air Force Armament Museum, Eglin Air Force Base, Florida[89] |
| 61-7960 | SR-71A | Castle Air Museum, Atwater, California |
| 61-7961 | SR-71A | Kansas Cosmosphere and Space Center, Hutchinson, Kansas |
| 61-7962 | SR-71A | American Air Museum in Britain, Imperial War Museum Duxford, Cambridgeshire, England[90] |
| 61-7963 | SR-71A | Beale Air Force Base, Marysville, California |
| 61-7964 | SR-71A | Strategic Air and Space Museum, Ashland, Nebraska |
| 61-7965 | SR-71A | Lost, 25 October 1967 |
| 61-7966 | SR-71A | Lost, 13 April 1967 |
| 61-7967 | SR-71A | Barksdale Air Force Base, Bossier City, Louisiana |
| 61-7968 | SR-71A | Virginia Aviation Museum, Richmond, Virginia |
| 61-7969 | SR-71A | Lost, 10 May 1970 |
| 61-7970 | SR-71A | Lost, 17 June 1970 |
| 61-7971 | SR-71A | Evergreen Aviation Museum, McMinnville, Oregon |
| 61-7972 | SR-71A | Steven F. Udvar-Hazy Center, Washington Dulles International Airport, Chantilly, Virginia |
| 61-7973 | SR-71A | Blackbird Airpark, Palmdale, California |
| 61-7974 | SR-71A | Lost, 21 April 1989 |
| 61-7975 | SR-71A | March Field Air Museum, Riverside, California[91] |
| 61-7976 | SR-71A | National Museum of the United States Air Force, Wright-Patterson Air Force Base, near Dayton, Ohio |
| 61-7977 | SR-71A | Lost, 10 October 1968 |
| 61-7978 | SR-71A | Lost, 20 July 1972[3] |
| 61-7979 | SR-71A | Lackland Air Force Base, San Antonio, Texas |
| 61-7980 | SR-71A | Dryden Flight Research Center, Edwards Air Force Base, California |
| 61-7981 | SR-71C | Hill Aerospace Museum, Hill Air Force Base, Ogden, Utah (formerly YF-12A 60-6934) |
Notes:
The Link Simulator Company's SR-71 Flight Simulator was developed during 1963–1965 under a deep "black" security blanket because it and the team Link assigned to it were given access to CIA OXCART and USAF R-12 / SR-71 clearances, the complete list of names of classified vendors supplying parts and software that had to be simulated, the total aircraft performance envelope data and a government-produced satellite photo montage of almost the entire continental United States to provide optical imagery for the RSO's portion of the Flight Simulator. This later capability was mounted on a separate, large, rectangular glass plate (approximately 6 feet (1.8 m) by 12 feet (3.7 m) in size) over which moved an optical sighting head that traveled at the scaled speed and direction of the Blackbird during its simulated flight. Realistic and accurate images were then displayed in the Optical View Sight and SLR RCD (Radar Correlator Display) in the RSO cockpit. Imagery was not provided to the pilot's simulator, which like the RSO simulator, had translucent window panels with varying degrees of lighting to change a simulated flight from daylight to night flying conditions.
Instructor positions were behind both the pilot's and the RSO's cockpits, with monitoring, malfunction and emergency problem controls provided. The simulator halves could be flown as separate cockpits with different training agendas or in a team mode, where intercom, instrument readings and air vehicle/sub-systems performance were integrated. Although most simulator flights were in a flight suit "shirt sleeve" environment, selected flights during a crew's checkout training were made with the crew wearing the complete David Clark Company's Full Pressure Suit.
In 1965, when the first Beale AFB Instructor Pilot/RSO crew (in civilian attire) visited the Flight Simulator during USAF checkout and acceptance trials at Link's upstate New York facilities, they were surprised to park in front of a busy, active grocery store and then be escorted to a side door that led to a hidden, rear portion of the building that was Link's classified "Skunkworks" type facility for the Blackbird program. Secrecy was so complete that no one in the township was aware of what was happening behind the busy checkout stands selling groceries. Later in 1965, the Flight Simulator was transferred to Beale AFB, California and the 9th Strategic Reconnaissance Wing's SAGE building, which provided vault level security for it plus the Wing Headquarters, Flight Mission Planning, and Intelligence Analysis / Exploitation of Blackbird mission products.
Besides SR-71 flight crew training and currency usage, the Flight Simulator was used several times by Lockheed and CIA operatives to analyze Groom Lake A-12 problems and accidents, with similar assistance provided for SR-71 flights at Edwards AFB. Another unique feature was that an actual flight mission tape for the SR-71 ANS could be loaded into the Flight Simulator's digital computers, which had been designed and programmed by Link engineers to emulate the Nortronics ANS. During Category II testing at Edwards AFB, some types of ANS navigation errors could be duplicated in the Flight Simulator at Beale AFB, with Link engineers then often assisting in software fixes to the main ANS flight software programs.
At the conclusion of SR-71 flying at Beale AFB, the Flight Simulator (minus the RSO optical imagery system) was transferred to the NASA Dryden facility at Edwards AFB in support of NASA SR-71 flight operations. Upon completion of all USAF and NASA SR-71 operations at Edwards, the Flight Simulator was moved in July 2006 to the Frontiers of Flight Museum on Love Field Airport in Dallas, Texas[93] and, with support from the Museum and Link (now, L-3 Communications, Link Simulation and Training), it is intended for viewing by Museum visitors.
|
|||||||||||||||||
|
||||||||||||||