Directory of U.S. Military Rockets and Missiles
Copyright © 2002 Andreas Parsch

Douglas GAM-87/AGM-48 Skybolt

After studies in 1958 had shown that it was feasible to air-launch ballistic missiles from high-flying strategic bombers, the USAF issued a requirement in 1959 for a long-range ALBM (Air-Launched Ballistic Missile). In May 1959, Douglas was awarded a development contract for the WS (Weapons System) 138A missile, designated GAM-87 Skybolt. Douglas subsequently awarded development subcontracts to Nortronics (guidance system), Aerojet General (propulsion), and General Electric (reentry vehicle). The GAM-87 was intended for use by the B-52H Statofortress and the British Vulcan B.2. Full-scale development was approved in February 1960, and in January 1961, the first drop tests of unpowered Skybolts occurred. Powered and guided flight tests of XGAM-87A prototypes began in April 1962, but the first five tests were all failures. The first fully successful Skybolt flight occurred on 19 December 1962, but on that same day the whole program was cancelled and the production of the operational GAM-87A stopped. Although Skybolt certainly had its technical difficulties and was well behind schedule, the cancellation was also very much influenced by economical and political factors.

Photo: USAF

The XGAM-87A was ballistic missile powered by a two-stage solid-fuel rocket motor and guided by a stellar-inertial navigation system. Each B-52H was to carry four GAM-87As, two each side-by-side on two underwing pylons. While on the pylon, the Skybolt was fitted with a tail cone to reduce aerodynamic drag. For launch, the missile was dropped from the pylon, the tail cone was ejected, and the first motor stage ignited. 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.

Limited flight tests with the remaining XGAM-87A missiles continued after program cancellation, and in June 1963, the XGAM-87A was redesignated as XAGM-48A. In total, Douglas built less than 100 Skybolt missiles.


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for XGAM-87A (XAGM-48A):

Length11.66 m (38 ft 3 in)
Finspan1.68 m (5 ft 6 in)
Diameter89 cm (35 in)
Weight5000 kg (11000 lb)
Speed15300 km/h (9500 mph)
Ceiling480+ km (300+ miles)
Range1850 km (1150 miles)
PropulsionAerojet Genaral two-stage solid-fueled rocket
WarheadW-59 thermonuclear (1.2 MT)

Main Sources

[1] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[2] Dennis R. Jenkins, Brian Rogers: "Boeing B-52G/H Stratofortress", Aerofax, 1990

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Last Updated: 19 February 2002