t used, on the Ye-152P.)810
The first flight of the interceptor prototype, "Ye-155-P1", took place on 9 September 1964.11 Development of the MiG-25, which represented a major step forward in Soviet aerodynamics, engineering and metallurgy, took several more years to complete.1112
The Mikoyan-Gurevich design bureau soon realized that the performance of the new aircraft gave it great potential to set new flight records. In addition to their normal duties, the prototypes Ye-155-P1, Ye-155-R1, Ye-155-R3 were made lighter by removing some unneeded equipment, and were used for these attempts. Under Federation Aeronautique Internationale (FAI) classification the Ye-155 type belonged to class C1 (III), which specifies jet-powered land planes with unlimited maximum take-off weight. Records set included:
- The first claim was for world speed records with no payload and payloads of 1,000 and 2,000 kilograms. Test pilot Alexander Fedotov reached an average speed of 2,319.12 km/h over a 1,000 km circuit in 16 March 1965.11
- For pure speed, with no payload, test pilot Mikhail M. Komarov averaged 2,981.5 km/h over a 500 km closed circuit on 5 October 1967.11 On the same day A. Fedotov reached an altitude of 29,977 metres (98,350 ft) with a 1,000 kilogram payload.14 The MiG eventually became the first aircraft to go higher than 35,000 metres (115,000 ft).14
- Time to height records were recorded on 4 June 1973 when Boris A. Orlov climbed to 20,000 m in 2 min 49.8 sec. The same day, Pyotr M. Ostapenko reached 25,000 m in 3 min 12.6 sec and 30,000 m in 4 min 3.86 sec.14
- On 25 July 1973, A. Fedotov reached 35,230m with 1,000 kg payload, and 36,240 m with no load (an absolute world record).14 In the thin air, the engines flamed out and the aircraft coasted on in a ballistic trajectory by inertia alone. At the apex the speed had dropped to 75 km/h.
- A few years later, on 31 August 1977, "Ye-266M" flown by MiG OKB Chief Test Pilot Alexander V. Fedotov, set the recognized absolute altitude record for a jet aircraft under its own power.15 He reached 37,650 metres (123,520 ft) at Podmoskovnoye, USSR in zoom climb (the absolute altitude record is different from the record for sustained altitude in horizontal flight). The aircraft was actually a MiG-25RB re-engined with the powerful R15BF2-300. It had earlier been part of the program to improve the aircraft's top speed that resulted in the MiG-25M prototype.6
In all 29 records were claimed, of which seven were all-time world records for time to height, altitudes of 20,000 m and higher, and speed. Several records still stand.6
Because of the thermal stresses incurred in flight above Mach 2, the Mikoyan-Gurevich OKB had difficulties choosing what materials to use for the aircraft. They had to use E-2 heat-resistant plexiglass for the canopy, and high-strength stainless steel for the wings and fuselage. Using titanium rather than steel would have been ideal, but it was expensive and difficult to work. The problem of cracks in welded titanium structures with thin walls could not be solved, so the heavier nickel steel was used instead. It cost far less than titanium and allowed for welding, along with heat resistant seals.6 The MiG-25 was constructed from 80% nickel steel alloy, 11% aluminium, and 9% titanium.16 The steel components were formed by a combination of spot-welding, automatic machine welding and hand arc welding methods.
Initially, the interceptor version was equipped with the TL-25 Smerch-A (also referred to as Product 720) radar, a development of the system carried by the earlier Tu-128. While powerful, and thus long-ranged and resistant to jamming, the system - due the age of its design and its intended purpose (tracking and targeting high- and fast-flying US bombers and reconnaissance aircraft), lacked Look-down/shoot-down capability, which limited its effectiveness against low-flying targets. By the time the MiG-25 entered service in 1969, this was a serious shortcoming, as strategic bombing doctrine was shifting towards low-level penetration of enemy territory. After Belenko's def