I'll write something later.
I said I would:
Project 4092/Glimmer/ISINGLASS was conceived as early as 1966 as a future replacement BDA aircraft for the NATO/Allied Atomic Force (the air-sea evolution of the Kennedy administration's Multilateral Force ballistic missile fleet) in lieu of the SR-71, which by 1970 had become standard in the West German
Luftwaffe, United States Air Force, French
Armee de l'Air, and Gallan
Marinen (Britain continued to use its Avro 730 for the strike/reconnaissance role until 1980 with the adoption of the "Bombcorde" missile carrier). The SR-71, while capable, was judged to be insufficient for high altitude, high speed overflights of the USSR in the coming 1980s. This was especially true as projections of a new "Super Foxbat" were being made with intelligence provided by Soviet defectors, equipped with more advanced air-to-air missiles that might significantly erode the SR-71's ability to penetrate deep behind Soviet lines.
Newer surface-to-air missiles such as SA-10 were also threatening the SR-71, although these were less efficient than the MiG-31, and considered able to be defeated by incremental improvements in ECM and simple high speed maneuvering.
In reality, the Soviet MiG-31 Foxhound was less of an evolutionary design than anticipated. Incorporating a phased array radar, ZASLON, and using the R-33 long-range missile it was capable of engaging up to four high speed (>Mach 3) targets from 500-90,000 feet, at ranges in excess of 150 km. This put the SR-71, and the Allied Atomic Force SLAMs, at significant threat. Both weapons were deemed obsolete by 1973 (although they remained in arsenals until the end of the first quarter of the 21st century) against increasing Soviet IADS threats.
While SR-71s were retained for immediate strike, anti-AWACS, and point target destruction with nuclear missiles, the aircraft's reconnaissance role was ended by 1978 with the development of the CIA backed, USAF funded ISINGLASS high speed reconnaissance aircraft.
The Isinglass was powered by a single Pratt and Whitney XLR-129 liquid fuel rocket engine (comparable in performance to the later American Space Shuttle Main Engine), producing 250,000 foot-pounds of force. The aircraft was piloted by a single man, and equipped with reaction control systems along its body and a pair of rudders and elevators for atmospheric maneuvering. It possessed little in the way of offensive countermeasures, relying on its high altitude, maneuvering ability, and suite of jamming equipment to defeat interception. Flying at over Mach 20, the aircraft had a radar cross section similar to a nuclear reentry vehicle. Recognising that such a provocation would result in potential atomic war, the original launch method of using a Titan booster was abandoned conceptually, but retained (and later used during the Bosnian War).
In a typical overflight reconnaissance mission, Isinglass/4092 was to be deployed via a C-141 Starlifter of the NATO Heavy Airlift Wing, based out of Luxembourg. The aircraft would be propelled to its operational altitude of 70 kilometers by the rocket engine, attaining a maximum velocity of 7.5 kilometers per second. Initial reentry would begin early, over Poland, and being a ballistic glide above the atmosphere over the Soviet Union. Cameras in the belly of the aircraft would capture images of silo fields, TEL installations, and military bases. The camera system specifically would be derived from the KH-4 "Corona" satellite system operated by the United States National Reconnaissance Office. Certain versions of 4092 such as SIGINT and ELINT packages were proposed.
ISINGLASS would begin full reentry once it was over Kamchatka and out of range of Soviet ABM missiles, and touch down at Groom Lake. Recovery and analysis of images and data collected would then begin.
Computer simulation modeling showed that 4092's high altitude and extreme speed rendered it totally immune to interception by Soviet anti-ballistic missiles with even limited maneuvering by the pilot. SA-5 Gammon, SA-10 Grumble, ABM-1 Galosh, and even a projected system called ABM-X (performance comparable to ABM-3 Gazelle system, with a larger warhead) were shown to be ineffective against the 4092 system.
Considered more expensive and hazardous than satellite operation, the US Congress balked at the $3b price tag, but heavy lobbying from the NATO Atomic Force pushed them to reconsider. Initial procurement of eight airframes began in 1975 and was completed in 1977.
Participating member states agreed to share funding for the program, and NATO adopted the ISINGLASS system in 1977. Atomic Force Level 2 participants (Galla, West Germany, United Kingdom, France) agreed to basing arrangements and prepared sites for emergency recovery of ISINGLASS flights. Eight aircraft were owned and operated by the United States Air Force and Central Intelligence Agency during its operation between 1977 and 2028. Two each were operated by the Level 2 partners, forming two squadrons of ISINGLASS aircraft.
The first combat use of the ISINGLASS aircraft was in 1977 during the Suez Conflict where NATO troops engaged Egyptian tank divisions and Soviet paratrooper "advisers" along the Suez Canal Zone and in the Sinai. ISINGLASS gathered valuable intelligence on Egyptian deployment of SS-1 "Scud" tactical nuclear missiles. When Port Said's near miss (the SS-1 hit the Med and nearly sinks HMS Bulwark with a 50 KT wave) was responded in kind by Atomic Force cruiser
Giuseppe Garibaldi with a single Polaris missile, ISINGLASS fully validated its design objectives of post-nuclear battle damage assessment. The destruction of Beni Suef and the Egyptian Scud missiles secured the canal for Allied use, broke the Egyptian morale, removed its strategic deterrent, and validated the Atomic Force's utility in tactical conflicts in a similar vein to the Easter Counteroffensive.
In Operation Desert Storm in 1992, the ISINGLASS system provided a photographic time table of Iraqi Army movements near Dammam, Saudi Arabia during the opening stages of the Second Gulf War on March 3rd, and gave Allied planners necessary intelligence to execute the breakout from the Dammam Perimeter and the following liberation of Kuwait.
During joint Soviet-NATO operations in Bosnia in 1993, Vandenburg Air Force Base deployed three overflights of ISINGLASS systems, providing accurate battlefield intelligence of Serbian troop movements which would normally disguise themselves from satellite surveillance.
No ISINGLASS aircraft was ever shot down or even engaged by air defence systems during its 51 years of operation.