Project Isinglass

Project Isinglass was the code name given to two heavily classified, crewed reconnaissance aircraft studied by the Central Intelligence Agency (CIA) as potential replacements for the Lockheed A-12 and SR-71 during the mid-1960s. The first proposal under the Isinglass name, a high-altitude plane to fly at Mach 4 – Mach 5 (4,900–6,100 km/h; 3,000–3,800 mph), was considered an insufficient advancement over existing aircraft; the second, much more advanced design, sometimes referred to as Project Rheinberry, was an air-launched, Mach 20 (24,500 km/h; 15,200 mph) rocket-powered boost-glide aircraft that would use a very-high-altitude trajectory to avoid defenses. This aircraft was considered too costly for development, and the project was abandoned in 1967.

Origins

Project Isinglass was developed as a result of the vulnerability of existing crewed reconnaissance aircraft, such as the Lockheed U-2 and the Lockheed A-12, to Soviet air defenses in the early 1960s, catalysed by the shooting down in May 1960 of Francis Gary Powers. Although there were continuing plans to overfly the Soviet Union with the A-12 – referred to by the CIA as Project Oxcart – these failed to come to pass, and the CIA began plans for an aircraft with superior performance to replace Oxcart.

The Convair proposal

The initial aircraft proposed under the Project Isinglass name was developed by the Convair division of General Dynamics, and was developed from work done on the Super Hustler, FISH, and Kingfish programs, as well as leveraging off work done on the F-111 tactical bomber. Convair's design utilised avionics and hydraulics systems that had been developed for use by the F-111, and was intended to be capable of cruising at speeds of Mach 4 to Mach 5, at an altitude of 98,000 ft (30 km). The feasibility study conducted by General Dynamics was completed in the fall of 1964; the aircraft was determined to be too costly, and was also still considered potentially vulnerable to projected Soviet air defense capabilities, so the project was halted.

The McDonnell proposal

Design and development

The Model 192 completed by McDonnell Aircraft in 1965 is usually considered part of Project Isinglass, however some documents refer to the aircraft as having been codenamed Project Rheinberry. McDonnell's proposed boost-glide aircraft, submitted to the CIA independently of the Convair Isinglass proposals, featured a small, crewed, rocket-powered craft with a high lift-to-drag ratio that would be air-launched by a B-52 bomber while flying over the Atlantic Ocean.