U-2 with its characteristic high aspect ratio wings, designed like some kind of a glider, was optimized for long-range high altitude flights.
SR-71 Blackbird (two-seated training version in the photo) – one of the most amazing aircraft ever built and real engineering wonder that came out Skunk Works facilities under brilliant lead of Clarence “Kelly” Johnson. Predominance as strategic level reconnaissance airplane, among others, realized through high-altitude and Mach 3+ flying.
How to penetrate with your own airplanes into the enemy’s airspace to attack the enemy? How to remain unnoticed and undisturbed above the enemy’s territory during operations of collecting top secret information – or better to say spying? Those were some of the main questions of airplane designers during the time of the Cold War.
At least until the dawn of intercontinental ballistic missiles and spy satellites, airplane will remain the main carrier of nuclear strike and the main subject of data collections about the enemy. The airplane performances that should have secured execution of the mentioned tasks, at least in one period of aviation, were the highest possible operational ceiling and the highest possible flight speed. However, high altitude flight operations with the flight speeds exceeding Mach 3, imposed on the airplane designers on both sides of the Iron curtain a whole range of design challenges. Still, the efforts resulted in some of the most fascinating aircraft in the history of aviation.
U-2 was probably the most famous American spy plane. This airplane was designed to fly at very high altitudes, thus securing that it stayed out of range of the Soviet surface-to-air missiles. U-2 was designed by a famous US airplane designer Clarence “Kelly” Johnson, at Lockheed secret installation named Skunk Works in Burbank, California. Johnson was one of the most famous American airplane designers. His brilliant ideas resulted in U-2, SR-71 Blackbird, F-104 Starfighter and many other airplanes.The main design feature of U-2 was its wings of big span and aspect ratio. Wings of such characteristics made U-2 look like a glider and let it fly at relatively high speeds at high altitudes, where density of air is very low.
The idea behind the design of U-2 came as a result of the American understanding that it was not possible to come into possession of secret information about the Soviet army using conventional methods. The infiltrated US secret agents were not successful enough and the evermore potent Soviet air defense prevented gathering of information from the air, unless spy planes could fly high enough to stay out of range of the Soviet surface-to-air missiles. Since 1953 the Americans have tried to collect data using hot air balloons. With the use of stable high-altitude jet stream balloons should have flown over the Soviet Union territory, taking pictures, and then jettison the recorded material over the territory of Japan. This method was quite unreliable, because balloons were exposed to atmospheric influences resulting in many balloons, with their spy equipment, falling into the hands of the Soviets.
On August 1, 1955 the top secret Lockheed U-2 spy plane took-off for the first time. The airplane was designed for and used by the American CIA – Central Intelligence Agency. One year after the first flight, U-2 started with high-altitude missions of flying over the Soviet territory, collecting data about the Soviet airbases and missile installations. U-2 could cruise at altitudes higher than 21,000 meters, up to 24,400 meters. Early missions were conducted from the bases in West Germany and covered the territory of northern and western portion of the Soviet Union. In 1957 full attention was devoted to Kaputsin Yar area, close to Volgograd, and to new cosmodrome Baikonur area. In these areas the Soviets initiated testing of their new intercontinental ballistic missiles and mid-range surface-to-surface missiles. The first aerial photos of Kaputsin Yar area were collected in 1953 by RAF Canberra reconnaissance airplane. On this occasion Canberra was severely damaged by the Soviet air defense. U-2 with its operational ceiling much higher than the service ceiling of Soviet MiGs was considered as the right choice for gathering of intelligence data above Kaputsin Yar and Baikonur zones. One section of U-2s was transferred to Turkey.
The strategy of collecting intelligence data flying over the Soviet territory was suddenly changed in 1960, because of two major events that undoubtedly confirmed the Soviet air defense power. On July 1, 1960 RB-47 spy plane was downed by two Soviet MiGs over the Barents Sea while two out of six crew members were captured. A much better known incident happened two months earlier. On May 1, 1960, on the spy route of one U-2 airplane the Soviet military installations were observed. The flight plan included taking off from Pakistan, flying over a few Soviet military facilities – among others, the Soviet factory of missiles in Tyuratam, and landing in Norway. However, the pilot Francis Gary Powers never reached in his U-2 his final destination in Norway. The Soviet SA-2 surface-to-air missile, the same that was to present the greatest threat to US aviators in the Vietnam War, downed Powers near the town of Sverdlovsk, deep inside the Soviet territory. This U-2 flight should have been the first US flight over the USSR in the mission of spying. Soon after downing Powers, the US government announced that the airplane was in the mission for NASA, collecting meteorological data in high altitudes. The truth was totally different. During the mission of collecting intelligence data, many Soviet fighters tried to down Powers in his U-2, firing air to-air-missiles, but without success. After 3 hours and 27 minutes, Powers felt an explosion in his proximity that ripped of his airplane’s tail section. U-2 was hit by SA-2 at the altitude of around 20 kilometers. Powers didn’t manage to activate the sequence for the destruction of airplane with its onboard equipment and the Soviets managed to recover the spy equipment out of plane wreckage, thus getting inevitable proof that the Americans were spying on them out of the Soviet airspace. Another fact and lesson learnt that came out of downing the U-2 was that flying at altitudes of even more than 20 kilometers is not safe anymore. RB-47 and U-2 incidents marked a turning point in the missions of spying during the Cold War era. The Americans had to promise they would abort missions of flying over the Soviet territory. A year later Gary Powers was released by the Soviets and in return the Americans released one Soviet spy that was held in US custody.
Considering that it became clear that flying above 20,000 meters did not provide immunity from the Soviet air defense, there was obvious need for finding out new ways of collecting intelligence data. In 1960 the Americans made the first operational success in using spy satellites and the Russians did the same three years later.
Although one U-2 was downed, the Americans did not abandon the idea of using an airplane for spying on the Soviet military installation; but what an airplane. The one that could fly three times the speed of sound at an altitude of more than 25 kilometers. One of the most famous airplanes in the history of aviation, although it existed under many designations and variants, the most notable was the one under designation of SR-71 Blackbird. Even today this airplane presents an absolutely mystic sight, although it was conceived in 1959 as a U-2 successor. Like U-2, SR-71 was designed by an ingenious team of scientists gathered around at the Skunk Works facilities. To materialize an airplane of SR-71 top performances, the US scientists had to create a technological miracle.
Until the mid-1960s USA had in operational use SR-71 strategic reconnaissance aircraft that reached performances of U-2 regarding the range and operational ceiling, but added to that a component of tremendous flight speed that could be continuously kept at the value of Mach 3.
The predecessor of SR-71 was A-12, designed by marvelous Kelly Johnson for CIA. This airplane took off in 1962, initially equipped with a weaker Pratt & Whitney J75 engines, considering that more powerful J58 still wasn’t ready for serial production. In total, thirteen A-12 were built. Based on A-12 design many other similar designs were delivered, like M-21, YF-12A, SR-71A, SR-71B and SR-71C. The most numerous was SR-71A that was built in twenty-nine exemplars. In total, and in all variants, there were fifty airplanes. Out of these fifty, twenty were lost in accidents.
Although A-12 had its maiden flight in 1962, the first SR-71 came into operational use not earlier than 1966, and the first mission of reconnaissance of enemy territory was in 1968.
Despite the fact that Blackbird was not seriously endangered by the Soviet air defense, thanks to its flight speed and high-altitude operations, SR-71 operated outside the Soviet borders. A typical mission consisted of flight near the Soviet border and collecting data from deep inside the adversary’s airspace thanks to high-tech radar, optical and sensor equipment installed onboard the SR-71. Although details about the installed equipment never went into public, there are official claims by the US Air Force that SR-71 could cover in one hour the ground area of 260,000 km2. In order to secure the longest possible flight range, soon after being airborne SR-71 would go for air refueling. After returning from the zone of action one more refueling would be performed; all in favor to prolong the time of being airborne. During the mission the flight speed of SR-71 was limited to Mach 3.2 although the airplane could reach even higher speeds. Its predecessor, A-12, could develop top flight speed of Mach 3.56 and the operational ceiling of more than 27,400 meters. Although the flight speed and altitude granted safe operation, unobstructed from the enemy’s air defense, the interception of SR-71 was tried out many times, but without real success. Still, optimally deployed Soviet anti-aircraft missile systems or MiG-25 interceptors posed some threat. With introduction of Soviet MiG-31 Foxhound interceptors, this threat became truly realistic.
SR-71 was strategically deployed in three airbases worldwide. This practically secured its presence in all areas of the US interest. From the Beale Air Force Base in California Cuba was monitored, Nicaragua for a shorter period, and the area of Middle East. From RAF airbase Mildenhall in England, the surveillance missions over the Baltic Sea, northern borders of the USSR and the Mediterranean were conducted. From Japanese base Kadena SR-71 were taking off on the missions of spying eastern Soviet territories, Vietnam, China and North Korea.
Top performances of SR-71 asked for fantastic properties of construction materials, design features, fuel, engines, and so on. For the moment it is enough to say that the US government ordered the destruction of all tools and technologies that were developed for designing and building SR-71s, from the moment the last planned SR-71 left the assembly lines. This way it was planned to prevent any possibility that top secret data ever finish in the hands of the Cold War opponents.
SR-71 remained the fastest manned turbojet airplane. On July 28, 1976, one SR-71 set absolute flight speed and altitude record for sustained horizontal flight. The reached flight speed was 3,529.56 km/h at the altitude of 25,929 meters. The pilot was Eldon W. Joersz and record still stands. On September 1, 1974 one SR-71 crossed the distance from New York to London in only 1 hour and 55 minutes; for the same distance the commercial supersonic Concorde needed 3 hours and 20 minutes, while Boeing 747 took around 7 hours. SR-71 holds coast-to-coast record as well – from the western to the eastern US coast it needed only 64 minutes. This last record was set on the route from Palmdale in California to Washington during the first retirement of SR-71 in 1990.
US Air Force retired the SR-71 fleet in January 1990, still some exemplars were reactivated temporarily in 1995, with operational service starting in 1997. Final retirement was in 1998.
Although during the time it became perfectly clear that fast development of ever more potent anti-aircraft missiles and systems threatens safe operation of even high performance airplanes like SR-71, the Americans did try to enter into service one more Mach 3+ capable airplane. This time it was a bomber, North American B-70 Valkyrie. B-70 had its maiden flight on September 21, 1964. In total, two prototypes were built and operated in flight – one was destroyed after mid-air collision with escort F-104 during trials. Like SR-71, B-70 was a colossal project. Unlike SR-71 that was mostly built from titanium, stainless steel was the material of choice for designing B-70; mostly because of very expensive and demanding technology for processing of titanium and limited budget at the same time. Regardless of the chosen material, days, weeks and months of frustrating efforts followed to develop suitable technologies and tools for cutting and joining stainless steel segments into sections. Flying at the speed of Mach 3 carries tremendous challenges for an airframe structure, mostly because of high temperatures that arise on the parts of airplane skin. The designers of B-70 finally managed to define and build a prototype airplane that reached top performances defined during the design phase. During the flying test trials over the American deserts B-70 provoked the most powerful shock waves ever caused by any airplane. There are a few reasons why the B-70 remained on the prototype level and never went into serial production or into operational units. The technology of processing construction material never came to a satisfying level – for example, welds of integral fuel tanks remained porous. The already mentioned high efficiency of new surface-to-air missiles put a great question mark whether such a costly project can actually be justified; B-70’s air dominance in adversary’s airspace would definitely be compromised. Also, there was the fact that in the mid-1960s the development of intercontinental ballistic missiles pushed aside bombers as carriers of nuclear strike.