The Douglas GAM-87A Skybolt was an air-launched ballistic missile (ALBM) developed during the late 1950s. It was intended to provide a mobile basing for the USAF's ICBM missile force by mounting them on heavy bombers rather than in fixed missile silos. A series of test failures and the development of submarine launched ballistic missiles (SLBMs) eventually led to its cancellation in the mid-1960s.
In 1958 several US contractors demonstrated that large ballistic missiles could be launched from strategic bombers at high altitude. The use of astronavigation systems for mid-flight corrections of an inertial guidance platform, similar to that of the US Navy's SLBM systems, led to an accuracy similar to that of their existing ground-based missiles.
The USAF was interested, and began accepting bids for development systems in early 1959. Douglas Aircraft received the prime contract in May, and in turn subcontracted to Northrop (guidance system), Aerojet (propulsion), and General Electric (reentry vehicle). Initially being known as WS-138A, in 1960 the project was given the name GAM-87 Skybolt.
At the same time the Royal Air Force was having problems with their IRBM missile project, Blue Streak. Not only was the missile long overdue and over budget, but the limited land area available on the British isles meant that it would be fairly easy for the USSR to find, and thus attack, the silos. They felt that the Skybolt would provide a much safer basing system, while at the same time allowing their V-bomber fleet to present a continued credible threat, with a long standoff range keeping them well away from the ever-increasing PVO Strany air defenses. This meant that their expensive Blue Steel II standoff missile, then under development, would not be needed. Prime Minister MacMillan met President Eisenhower and agreed to purchase 144 Skybolts for the RAF, and Blue Streak and Blue Steel II were both cancelled. By agreement, British funding for research and development was limited to that required to modify the V-bombers to take the missile.
The GAM-87 was powered by a two-stage solid-fuel rocket motor and was intended to be launched by a B-52H heavy bomber. Each B-52H was to carry four missiles, two under each wing on side-by-side pylons, while the Avro Vulcan carried one each on smaller pylons. The missile was fitted with a tailcone to reduce drag while on the pylon, which was ejected shortly after being dropped from the plane. After first stage burnout, the Skybolt coasted for a while before the second stage ignited. First stage control was by movable tail fins, while the second stage was equipped with a gimballed nozzle.
By 1961, several test articles were ready for testing from USAF B-52 bombers, with drop-tests starting in January. In England compatibility trials with mockups started on the Vulcan. Powered tests started in April 1962, but the test series went badly, with the first five trials ending in failure.
The first fully successful flight occurred on December 19, 1962, but on that same day the whole program was cancelled and the production of the operational GAM-87A stopped. The U.S. simply no longer needed the missile, with improved silo-based missiles and submarine-launched ballistic missiles (SLBMs) making their counterforce largely invulnerable anyway.
This left the British with no credible nuclear deterrent. The program was offered to the British to continue funding, but instead they bought the Polaris SLBM, passing control of the nuclear deterrent from the RAF largely to the Royal Navy. The RAF kept a tactical nuclear capability with the WE.177 which armed V Bombers and later the Panavia Tornado force. The cancellation contributed significantly to the decline of Harold Macmillan's administration.
Limited flight tests with the remaining XGAM-87A missiles continued after program cancellation. In June 1963, the XGAM-87A was redesignated as XAGM-48A.
- Length: 11.66 m (38 ft 3 in)
- Span: 1.68 m (5 ft 6 in)
- Diameter: 89 cm (35 in)
- Weight: 5,000 kg (11,000 lb)
- Speed: 15,300 km/h (9,500 mph)
- Ceiling: 480+ km (300+ miles)
- Range: 1,850 km (1,150 miles)
- Propulsion: Aerojet General two-stage solid-fueled rocket
- Warhead: W-59 1.2 MT thermonuclear
- M- sequence missiles: AGM-45 - MIM-46 - AIM-47 - AGM-48 - LIM-49 - RIM-50 - MGM-51
- B- sequence missiles: XRM-84 - XRM-85 - XRM-86 - GAM-87 - SRM-88 - XRM-89 - XRM-90
- Neustadt, Richard E. Report to JFK: The Skybolt Crisis in Perspective. Ithaca, NY: Cornell University Press, 1999. ISBN 0-8014-3622-2.
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It uses material from the Wikipedia article "AGM-48 Skybolt".