The SR-71(Bx), a Blackbird supercruising strike aircraft equipped with AGM-69A SRAM missiles

Ben Rich of Lockheed Skunk Works presented a paper in 1976 that provided a brief overview of the “Bx,” a straightforward modification of the SR-71 Blackbird into a supercruising strike aircraft

The Lockheed A-12 and YF-12A aircraft served as the basis for the development of the SR-71, also referred to as the “Blackbird,” or long-range, advanced strategic reconnaissance aircraft. The 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, California, received the first SR-71 to begin service in January 1966. The first SR-71 flight took place on December 22, 1964. On January 26, 1990, the US Air Force (USAF) retired its fleet of SR-71 aircraft.

For almost 24 years, the SR-71 held the record for being the fastest and highest-flying operational aircraft in the world. It could cover 100,000 square miles of the Earth’s surface per hour from 80,000 feet.

According to Scott Lowther’s narrative in the book Origins and Evolution Lockheed SR-71 Blackbird, Ben Rich of Lockheed Skunk Works presented a paper in 1976 that provided a brief overview of the ‘Bx,’ a straightforward modification of the SR-71 into a supercruising strike aircraft. This would be achieved by installing AGM-69A SRAM missiles in the Chinese equipment bays, which are slightly different from the current ones, in longer bays that are roughly in the same locations.

The SR-71(Bx) diagram that is currently available has very poor resolution and contains a few internal contradictions, but it looks like the aircraft’s forward fuselage would be “bent” upwards in addition to having rounded undersides and blunter chines to give the missiles enough room. The aircraft would have been fitted with a dedicated radar, though it’s difficult to make out the details; the nose would be recontoured and slightly lengthened to accommodate.

There is limited information available on the SR-71(Bx). It is not clear how much effort was put into its design. However, launching at Mach 3.2 and an altitude of 80,000ft could increase the range of the SRAM to approximately 500 nautical miles. The SRAM was not a guided missile, so its accuracy was not spectacular. At a distance of 300 nautical miles, the Circular Error Probability (CEP) was 3600ft. Rich proposed that CEP could be reduced by half with terminal guidance, but the specifics of this were not provided.

Origins and Evolution Lockheed SR-71 Blackbird is published by Mortons Books and is available to order here.

Photo by U.S. Air Force and Scott Lowther via Mortons Books