Lockheed SR-71 Blackbird and its relatives
Before I started writing this article, I thought that the Lockheed SR-71 was a separate, unique project. I was wrong, it was not like that.
Start
The Lockheed SR-71 project had a difficult beginning, and its history must begin with… the Junkers Ju.86P, or more precisely the high-altitude reconnaissance aircraft Ju.86P-2. With its maximum flight altitude of 12,000 meters, it was out of reach of either anti-aircraft artillery or serial fighters until 1943.
By the mid-1950s, the CIA needed the same, only better and differentand Kelly Johnson (Clarence Leonard “Kelly” Johnson) of the Lockheed Skunk Works did a brilliant job building the Lockheed U-2. Its later variant, the ER-2, is still in service today NASA – ER-2 Earth Resources
From U-2 to A-12
The CIA initially wanted to improve the subsonic high-altitude U-2, which had been flying successfully since 1955, and from 1956 to 1960 brought back images of the territory of the USSR, but to make it less visible to radar, and began Project RAINBOW.
First, the U-2 was covered in an absorbent radio coating (Project Wallpaper), then wires were placed on plastic poles (Project Trapeze), and more wires were added during Project Wires.
Together, these measures cost the U-2 5,000 feet (1,500 meters) of maximum altitude, 20% of its range, and added to the engine overheating. The result was the loss of the prototype on April 4, 1957. U2 'Article 341', with pilot Robert Sieker.
Technology has not stood still, and the project Paragraph The Article or the Angel evolved gradually.
The new project was given the name Archangel, and thus the U-3 project, also known as A-1, the first of the development options, appeared.
It was followed by the A-2, 3, 4, up to the A-12. The CIA requested designs from Lockheed and Convair, Convair submitted the Kingfish design, Lockheed the A-12.
The choice of the winner was based not only on the project itself, but also on the personalities of the designers and the reputation of the company.
Lockheed designed and produced the U-2 on contract, in secrecy, and on budget.
Convair had recently gone over budget on the B-58 bomber and did not have a secret R&D unit ready like Lockheed's Skunk Works.
On August 28, 1959, designer Clarence “Kelly” Johnson was informed that the Lockheed A-12 had won the competition.
On January 26, 1960, the CIA officially ordered 12 Lockheed A-12 aircraft. A total of 18 single-seat A-12s were built, of which:
12 A-12,
1 two-seat training Titan Goose,
2 M-21 drone carriers,
3 YF-12A interceptor prototypes.
The aircraft turned out to be quite good, and after replacing the engines with Pratt & Whitney J58, it reached a ceiling of 85,000 feet (26,000 meters) and a speed of 3.2 – 3.2 times the speed of sound (4075 km / h), which allowed it to escape from S-75 missiles when flying over North Vietnam. It was decided not to launch it over the USSR.
In addition to the hope for speed and altitude, the aircraft was also equipped with electronic countermeasures equipment.
The payload included one of three types of cameras:
Type I System by Perkin-Elmer Corporation,
Type II System by Eastman-Kodak Co.,
Type III System by Hycon Corporation.
The Perkin-Elmer Corporation camera included two cameras mounted on a stabilized platform.
Military: We don't like the North American XB-70 Valkyrie, give us another one
In January 1954, Boeing ordered RAND Corporation (ah, these old names, i miss them) a study on the topic of “a next-generation bomber, but not the exoatmospheric MX-2145.” As a result of the study, it was decided that the next bomber must necessarily be supersonic.
Hidden text
There are several understandings of the term “supersonic”. An aircraft can be “supersonic with afterburner, but not for long”, or “supersonic as normal\cruise mode”. For 5th generation aircraft, the requirements “supersonic as normal mode without using afterburner\afterburner” are added.
An afterburner is simple (no). It is fuel injection behind the turbine, with heating of the gas flow at the outlet. This significantly increases thrust, but turns a turbojet into a jet (Ramjet), but at the same time fuel consumption increases sharply.
The US Air Force read the report and ordered R&D for Weapon System 110A, a bomber with the range of the B-52 and the speed of Mach 2, like the Convair B-58 Hustler. In July 1955, the US Air Force ordered two prototypes, one from Boeing and one from North American Aviation. At the time, these were still two different companies.
In March 1957, based on the results of other work and tests, the requirements were revised, and now they wanted the bomber to fly at three speeds of sound. On September 18, 1957, the requirements were clarified once again:
Cruising speed 3..3.2 speed of sound
Flight altitude 70,000–75,000 feet (21,000–23,000 meters),
Range up to 10,500 miles (16,900 km),
Takeoff weight not exceeding 490,000 pounds (220,000 kg).
On January 23, 1957, North American Aviation was declared the winner of the competition, and on January 24, 1958, a contract was signed for “Phase 1”, but…
It turned outthat the new fuel, Zip-fuel (high energy fuel (HEF)), based on borohydride additives, is not only expensive, expensive even for rich military men, but also turns into 1) toxic 2) abrasive after combustion. With a corresponding drop in engine operating time before replacement, and problems with maintenance.
It was decided that the altitude of 20 kilometers was no longer a defense against missiles, so the air defense breakthrough would be at a low altitude. In 1959, this was considered to be an altitude of 600 meters (2,000 feet).
It turned outthat the B-70 at this altitude cannot even reach supersonic speed, with a limit of 0.95 speed of sound, slightly faster than the B-52.
It turned out that the new program will be very, very expensive. Even for the US.
The transition of the medium-range bomber from the Boeing B-47 Stratojet to the Convair B-58 Hustler showed that the B-58 cost three times as much to develop and operate as the B-52, along with its increased size and fuel consumption.
In December 1959 the program XB-70 Valkyrie officially reduced to one prototype. Five years of bargaining followed over how much more money to spend on the already closed project, whether to build another 11 YB-70s or not. The program was changed for political reasons, and they bargained for it in Congress. In the end, two were built. The first of them took off on September 21, 1964 and flew until it was transferred to the museum on February 4, 1969 (National Museum of the United States Air Force, Wright-Patterson Air Force Base), the second crashed on June 8, 1966.
The future belonged to missiles – they were cheaper, faster, and were ready 24/7.
Curtis Emerson LeMay reappears on the scene
A man of great soul, the organizer of the mass bombing of Japan – Japan's losses from them are not counted, estimated at 240 to 900 thousand killed, 200 thousand to 1 million wounded, 8.5 million left homeless. The organizer of the mining of Japanese ports – Operation Starvation, which left Japan almost without supplies.
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Organizer of Operation Meetinghouse – the burning of Tokyo on March 9-10, 1945. The bombing of Hiroshima and Nagasaki resulted in large one-time losses, but Japan's total losses from traditional air warfare were 2-3 times higher. Organizer of the airlift during the Berlin blockade, organizer of the restructuring of the US Air Force.
He requested that, instead of the cancelled XB-70 Valkyrie program, a bomber and reconnaissance version of the A-12 be developed. The bomber version was eventually cancelled, but the strategic reconnaissance R-12, which became the SR-71, remained.
SR-71 – unique in every way
The plane turned out to be truly unique.
Slightly longer than the A-12 (32.74 meters versus 30.96 meters – primarily due to the second cabin, the A-12 was a single-seater, except for 1 training aircraft), slightly heavier (78.018 kg versus 53.070 kg).
Carried slightly more fuel – 12,219.2 US gal (weight not specified, 35,746 kg by conversion) versus 10,590 US gal (30,980 kg). With an excellent appetite – with refueling after 90 minutes of flight at cruising supersonic speed of 3.2 mach.
Titanium for it had to be bought in the USSR through front companies. The shape of the body (or rather, the radar cross-section (RCS) was reduced to 10 square meters, paint and electronic warfare made it not yet invisible, but brought it closer to it. They decided not to launch it for flights over the USSR, and the satellites Keyhole KH4 Corona, Keyhole KH-7 Gambit, Keyhole KH-8 Gambit 3 and then KH-11 KENNEN, which gave the world a mirror for the Hubble Space Telescope, were already in production and flying.
During the flight, the plane heated up to 300-315 degrees, which is why the ground assembly was carried out with huge tolerances, and all the connections were constantly leaking. Urban legend says that because of this, the plane had to be refueled immediately after takeoff – this is not entirely true, but the plane leaked, and took off with incomplete tanks to reduce the load on the brakes, tires, and to be able to land if the engine failed during takeoff.
The engines were also unique (Pratt & Whitney J58 – JT11D-20J or JT11D-20K), and not only because of the afterburner system. It is not exactly a turbojet engine, or rather, not a turbojet at all, a turboramjet. To ensure the engines restart, triethylborane (TEB) injection had to be used.
Triethylborane had to be used, among other things, because JP-7 fuel (Turbine Fuel Low Volatility JP-7) evaporates extremely poorly, ignites poorly, and is, in the case of the SR-71, also an insect repellent (FLIT), a coolant for the cabin air conditioning system, a coolant for the airframe itself, and a coolant for the chassis compartment. JP-7 is not aviation kerosene, although J58 can run on regular aviation kerosene of those years (JP-4 kerosene-gasoline and JP-5 – kerosene with additives), in the event of the lack of the possibility of refueling from a special air tanker, with a maximum speed limit of Mach 1.5.
Hidden text
For the same purposes, the flying grocery store created in the USSR had to be filled with alcohol – two 125-liter tanks for cooling – 40/60% alcohol, plus 20 liters in the pylon for the R-40T seeker, and there are 4 of them, plus separate cooling of the electronic warfare for the RB variant, depending on which variant we are talking about.
The engines were controlled automatically, the nose cone position was adjusted, reducing the air speed in the turbine to subsonic. The analog control system for the air intake cone position (stability augmentation system (SAS)) was replaced by a digital one (Digital Automatic Flight and Inlet Control System (DAFICS)) by 1980.
The aircraft was equipped with an astro-inertial guidance system (ANS) from Nortronics (Northrop Corporation), with an onboard computer for 56, then 61 stars (ephemeris, of course), giving an accuracy of about 1000 feet (300 meters). The system was taken from the SM-62 Snark and AGM-48 Skybolt missiles and modified, obtaining NAS 14V2.
The body of the plane itself was almost a solid fuel tank – more precisely, 6 groups, 9 tanks.
Let's give the floor to Kelly Johnson – talks about his greatest creation the SR-71, Uncut interview. | Stock Footage, where he talks about fuel tanks, and about the engine control system, which automatically shut down both engines when one failed, and automatically compensated for the roll due to lack of thrust, and about the classic slide rule in the design.
Separately, it is necessary to mention the full pressure suits developed specifically for the A-12 / SR-71 program – just recently, on July 28, 2021, test veteran Bill Weaver died (Lockheed test pilot Bill Weaver, Dec 6, 1928 – July 28, 2021), who survived a fall from 23.7 km (78,000 feet) on January 25, 1966 wearing such a spacesuit.
The Right Stuff
His SR-71B broke apart in mid-air due to a control system failure at 3.2 Mach 1. The pilot was thrown out of the plane, along with his seat, the ejection system was not activated. After falling from 23 kilometers to about 7.8, the pilot regained consciousness, at an altitude of 4.5 kilometers (15,000 feet) the automatic parachute system was activated. The second crew member, Jim Zwayer, a company test navigation and systems specialist, died in this incident.
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From 1983: Chuck Yeager on “The Right Stuff”.
Brigadier General Charles Elwood Yeager (/ˈjeɪɡər/ YAY-gər, February 13, 1923 – December 7, 2020)
The camera equipment also differed from the A-12, with either Itek's Operational Objective Cameras, or Itek Optical Bar Camera, plus a separate HYCON Technical Objective Camera (TEOC).
The originally delivered Side-looking airborne radar (SLAR) was replaced by Loral's Advanced Synthetic Aperture Radar System (ASARS-1), both radars intended for radar terrain mapping.
Interceptions
During operations in Europe, the SR-71 was used on two routes, the first over the coast of Norway and the Kola Bay and the second, the Baltic Express.
The Baltic Express was supposed to take off from England, fly over Jutland, the Danish straits, pass through the international corridor to the Aland Islands, and pass back to Denmark over the coast of Sweden. Due to the impossibility of accelerating to its 3.2 speed of sound (since when turning at such a speed the aircraft inevitably flew into foreign airspace), the SR-71 crawled at an altitude of 2.54 and 22 kilometers. In such conditions, with ground guidance, it was repeatedly intercepted by the MiG-25, reaching an altitude of 19 km and a distance of up to 3 km.
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Speaking about the possibility of intercepting the SR-71 by a crew of 2-4 MiG-25, it is necessary to understand that the early versions of the MiG-25 had ground guidance – the onboard equipment “Lazur-M” of the target guidance system “Air-1”. The onboard radar of the first variants of the RP-25 “Smerch-A” product 720, had a declared detection range of a target with an EPR of 16 m2 – 100 km.
Considering that the EPR differs for different frequencies, target acquisition with an EPR of 10 m2 is not guaranteed at the range when the MiG computer would have had time to make a decision on launch, and during the time when the R-40T IR seeker would have had time to acquire the target.
With the R-40T launch range of 30..50 kilometers on a head-on course, and a combined speed of 2.8 + 3.2 – about 6 Machs, or 2 kilometers per second, there is no guarantee that a decision will be made in 30/2 ..50/2 – 15..25 seconds. The operation of the ground guidance line was already suppressed in Vietnam by electronic warfare means, for example, by the QRC-128 suspended containers on the F-105F, so the effectiveness of ground guidance is questionable. Separately, it is necessary to consider the question of whether the R-40T IR seeker is capable of capturing the SR-71 at such a range, and how effective the SR-71's electronic warfare means would be.
The Swedes, in turn, also did not miss the opportunity to try to intercept the SR-71 with their Saab 37 Viggens, accelerating to the maximum 2.1 Mach, and making a dynamic hill from 18 kilometers, to capture the target with a guidance radar. According to the Swedish Air Force, in 322 express flights from 1977 to 1988, in 51 cases the capture was successful.
On June 29, 1987, during one of these flights, one of the SR-71 engines failed. NSA (National Security Agency) data declassified 30 years later indicate that the MiG-25 intercepted the damaged SR-71, but. By this time, it was already escorted by two Swedish Saab JA 37 Viggens, which thwarted the interception. A little later, they were replaced by two more Saabs, which escorted the SR-71 (AF serial number 61-7964, Lt. Cols. Duane Noll and Tom Veltri ) to Danish airspace. The plane itself landed in Nordholz, Germany.
End of an era
The first talks about retiring the SR-71 and sending it to a museum began in 1988. The program was closed in late 1989. Three aircraft were taken out of storage in 1993, in 1997 Bill Clinton cancelled additional funding, and in 1998 the program was finally closed. NASA used two SR-71s until 1999, when they were sent to a museum – Dryden Flight Research Center (Armstrong Flight Research Center).
The reasons are the same – money. The Army wanted to receive not strategic data after 2-3 days (while the plane was landing, the films would be unloaded and brought for development), but tactical data, in real time. The U-2 was re-equipped with new communication systems, the SR-71 was not. The Air Force began developing UAVs back in 1983 – when Lockheed released a report – Design of Long Endurance Unmanned Airplanes Incorporating Solar and fuel cell propulsion (1984). The result was the UAVs – Northrop Grumman RQ-4 Global Hawk and Lockheed Martin RQ-3 DarkStar.
Of the 32 SR-71 aircraft built, 11 were lost, and the remaining 21 are in museums.
Of the 15 production A-12s (and a total of 18 including 3 YF-12s), 6 were lost, 9 are in museums and exhibits, including one at CIA headquarters, Langley, Virginia.
Of the 3 YF-12s, 1 was lost, 2 are in museums.
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