One of the latest known ideas for creating an interceptor variant of the Blackbird was the `SR-71 I’, proposed by Lockheed to the USAF in November 1982. This design called for the use of the new AIM-120 AMRAAM.
The SR-71, unofficially known as the “Blackbird,” is a long-range, advanced, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft. The first flight of an SR-71 took place on Dec. 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, Calif., in January 1966. The US Air Force (USAF) retired its fleet of SR-71s on Jan. 26, 1990.
Throughout its nearly 24-year career, the SR-71 remained the world’s fastest and highest-flying operational aircraft. From 80,000 feet, it could survey 100,000 square miles of Earth’s surface per hour.
As told by Scott Lowther in the book Origins and Evolution Lockheed SR-71 Blackbird, in September of 1980, Analytic Services, Inc. (usually known as ANSER, a non-profit corporation formed in 1958 as a sort of ‘think tank’ to aid the US Air Force) produced a presentation on the use of the SR-71 as a long-range interceptor. The SR-71 would be equipped with four AIM-54 Phoenix missiles — the inheritors of the AIM-47 Falcon legacy – and the AWG-9 radar for the purposes of reaching out and destroying Soviet AWACS aircraft. The presentation was unfortunately thin on details about configuration changes, though it noted that the nose would need to be re-contoured; options also included changing the engines to F100 or F101 turbofans and stretching the fuselage. The Phoenix missiles would be carried within the internal bays, but external carriage under the rear fuselage was also touched upon. The Phoenix missiles would require folding fins to fit within the SR-71 bays. This study seems to have been largely back of the envelope.
One of the latest known ideas for creating an interceptor variant of the Blackbird was the `SR-71 I’, proposed by Lockheed to the USAF in November 1982. This design called for the use of the new AIM-120 AMRAAM (Advanced Medium Range Air-to-Air Missile). The AIM-120 was essentially the same size as the AIM-7E/F Sparrow without requiring the complexity of folding fins. The Sparrow missile required that the target be illuminated by the radar unit in the aircraft, while the AIM-120 had its own radar transmitter. Thus, it was a ‘fire and forget’ missile. A bonus was that since the aircraft’s radar did not need to constantly track a single target until the missile hit it, multiple enemy aircraft could be tracked and targeted simultaneously. In order to support the new AIM-120 missiles, the SR-71 I would be equipped with the AN/APG-65 radar used on the F/A-18 Hornet. The 27in diameter circular planar array antenna would be modified into a slightly larger 32in diameter, slightly non-circular shape. The increased area permitted detection of large aircraft out to around 100 nautical miles, with a tracking range of 80 nautical miles. The AIM-120 missiles would have modified fins to fit within the SR-71 bays, and would have a range of about 80 nautical miles.
The purpose of the SR-71 I was to serve as a long-range high-speed interceptor of the latest generation of Soviet AWACS planes and, as a secondary purpose, to intercept Blackjack and Backfire bombers. Speed and range were such that incoming bombers could be intercepted prior to their getting close enough to the continental United States to launch their own air-to-surface missiles. It was proposed that the SR-71 I operate out of either Loring Air Force Base in northeastern Maine or Sawyer Air Force Base in Michigan (now decommissioned). From there, with a single refuelling, the SR-71 I could reach and attack Soviet targets in the region of Scandinavia and be recovered in either Thule Air Base in northern Greenland or RAF Mildenhall in Suffolk, England. One wonders whether either of these landing sites would have been anything but smoking radioactive holes by the time the SR-71 Is got it there, given the likely outcome of USAF interceptors shooting down Soviet AWACS and bombers.
Lockheed did not propose to build all-new aircraft, but to modify seven existing SR-71A airframes. These seven aircraft would all be based at the same location.
Origins and Evolution Lockheed SR-71 Blackbird is published by Mortons Books and is available to order here.
Photo credit: U.S. Air Force and Scott Lowther via Mortons Books
The YF-12 carried the AIM-47A Falcon. The precursor to the AIM-54 Phoenix. The AMRAAM AIM-120 was not produced until about 1991.