The Mikoyan-Gurevich MiG-25 (Russian: Микоян и Гуревич МиГ-25) (NATO reporting name: Foxbat) is a supersonic interceptor and reconnaissance aircraft that was among the fastest military aircraft to enter service. It was designed by the Soviet Union's Mikoyan-Gurevich bureau. The first prototype flew in 1964, and the aircraft entered into service in 1970. It has a top speed of Mach 2.83 (as high as Mach 3.2, but at risk of significant damage to the engines), and features a powerful radar and four air-to-air missiles.
When first seen in reconnaissance photography, the large wing planform suggested an enormous and highly maneuverable fighter, at a time when U.S. design theories were also evolving towards higher maneuverability due to combat performance in the Vietnam War. The appearance of the MiG-25 sparked serious concern in the West and prompted dramatic increases in performance for the McDonnell Douglas F-15 Eagle then under development in late 1960s. The capabilities of the MiG-25 were better understood in 1976 when Soviet pilot Viktor Belenko defected in a MiG-25 to the United States via Japan. It turned out that the weight of the aircraft necessitated large wings.
Production of the MiG-25 series ended in 1984 after completion of 1,190 aircraft. A symbol of the Cold War, the MiG-25 flew with Soviet allies and former Soviet republics, remaining in limited service in Russia and several other nations. It is the second fastest and second highest-flying military aircraft ever fielded after the SR-71 reconnaissance aircraft.
Design and development
During the Cold War, Soviet Air Defence Forces, PVO (not to be confused with Soviet Air Force, VVS) was given the task of strategic air defense of the USSR. In the decades after World War II, this meant not only dealing with accidental border violations, but more importantly defending the vast airspace of the USSR against US reconnaissance aircraft and strategic bombers carrying free-fall nuclear bombs. The performance of these types of aircraft was steadily improved. Overflights by the very high altitude American Lockheed U-2 in the late 1950s revealed a need for higher altitude interceptor aircraft than currently available.
The subsonic Boeing B-47 Stratojet and Boeing B-52 Stratofortress strategic bombers were followed by the Mach 2-capable Convair B-58 Hustler, with the even faster North American B-70 Valkyrie on the drawing board. A major upgrade in the PVO defence system was required, and at the start of 1958 a requirement was issued for manned interceptors capable of reaching 3,000 km/h and heights of up to 27 km (88,583 ft). Mikoyan and Sukhoi responded.
YE-152 and YE-152M experimental interceptor
The Mikoyan-Gurevich OKB had been working on a series of interceptors during the second half of the 1950s: the I-1, I-3U, I-7U, I-75, Ye-150, Ye-150A, Ye-152, Ye-152A, Ye-152P, and Ye-152M. The Ye-150 was noteworthy because it was built specifically to test the Tumansky R-15 engine, two of which would later be used for the MiG-25. This led to Ye-152, alternatively known as Ye-166, which set several world records. The Ye-152M (converted from one of the two Ye-152 aircraft) was intended to be the definite heavy interceptor design. But before it was finished, the PVO had selected the Tupolev Tu-128. As the work on the MiG-25 was well under way, the single-engine Ye-152M was abandoned.
Designing a new interceptor
Work on the new Soviet interceptor that became the MiG-25 started in mid-1959, a year before Soviet intelligence learned of the American Mach 3 A-12 reconnaissance aircraft. It is not clear if the design was influenced by the American A-5 Vigilante.
The design bureau studied several possible layouts for the new aircraft. One had the engines located side-by-side, as on the MiG-19. The second had a stepped arrangement with one engine amidships, with exhaust under the fuselage, and another in the aft fuselage. The third project had an engine arrangement similar to that of the English Electric Lightning, with two engines stacked vertically. Option two and three were both rejected because the size of the engines meant any of them would result in a very tall aircraft which would complicate maintenance.
The idea of placing the engines in underwing nacelles was also rejected because of the dangers of any thrust asymmetry during flight. Having decided on engine configuration, there was thought of giving the machine variable-sweep wings and a second crew member, a navigator. Variable geometry would improve maneuverability at subsonic speed, but at the cost of decreased fuel tank capacity. Because the reconnaissance aircraft would operate at high speed and high altitude the idea was soon dropped. Another interesting but impractical idea was to improve the field performance using two RD36-35 lift-jets. Vertical takeoff and landing would allow for use of damaged runways during wartime and was studied on both sides of the Iron Curtain. The problem has always been that engines dedicated to vertical lift do not contribute with any power in horizontal flight, and occupy space in the airframe needed for fuel. The MiG interceptor would need all the fuel it could get, so the idea was abandoned.
Ye-155R3 Reconnaissance prototype with a 5,280 litre drop tank under the belly, 1964
The first prototype was a reconnaissance variant, designated "Ye-155-R1", that made its first flight on 6 March 1964. It had some characteristics that were unique to that prototype, and some of these were visually very evident: the wings had fixed wingtip tanks (600 litre capacity) to which small winglets were attached for stability purposes, but when it was found that fuel sloshing around in the tanks caused vibrations they were eliminated. The aircraft also had attachments for movable foreplanes, canards, to help with pitch control at high speed (provisions for canards had previously been installed, but not used, on the Ye-152P.)
The first flight of the interceptor prototype, "Ye-155-P1", took place on 9 September 1964. Development of the MiG-25, which represented a major step forward in Soviet aerodynamics,engineering and metallurgy, took several more years to complete.
On 9 July 1967, the new aircraft was first shown to the public at the Domodedovo air show, with four prototypes (three fighters and a reconnaissance aircraft) making a flypast.