Missile AGM-129 ACM

The AGM-129 ACM (Advanced Cruise Missile) was a subsonic, turbofan-powered, air-launched cruise missile with reduced radar and infrared signatures. Development studies began in 1982 after the US Air Force concluded that the AGM-86B, which relied on low-altitude penetration, would be unable to defeat future Soviet air defenses. The introduction of airborne early warning aircraft and look-down/shoot-down radars — the Zaslon PESA on the MiG-31 and the Myech on the Su-27 — reduced the probability that a low-flying AGM-86B would reach its target. A development contract was awarded in 1983, the first test missile flew in July 1985, and the first production rounds were delivered in 1987. The program suffered hardware quality-control failures and testing mishaps; Congress zeroed out funding in 1989, and deliveries were halted in 1989 and 1991. Planned procurement of enough missiles to replace the roughly 1,461 AGM-86Bs was cut in January 1992 to 640 rounds and later to 460. In 1989 the United States obtained Canadian permission to conduct AGM-129A test flights over Canadian territory.

The airframe used body shaping to reduce radar cross section, with the engine air intake flush-mounted on the underside. Exhaust was shielded by the tail surfaces and cooled by a diffuser to suppress the infrared signature. The radar altimeter arrangement of the AGM-86B was replaced by inertial navigation combined with terrain contour matching (TERCOM), with velocity updates from a lidar Doppler velocimeter, eliminating emissions that could betray the missile. Quoted circular error probable was 100 to 300 ft (30 to 90 m). The F112-WR-100 turbofan increased range by approximately 50 percent over the AGM-86B, and the reduced signature permitted flight at higher altitudes. The AGM-129A carried the W80-1 variable-yield nuclear warhead.

Two further variants were designated. The AGM-129B was defined as an AGM-129A with structural and software changes and an alternate nuclear warhead for a classified mission; the Air Force sought to convert 120 missiles from 1985, Congress denied the request in 1991, and the effort was restarted by Defense Department direction in 1992. Some sources describe the AGM-129B instead as a conventional variant, a role ultimately filled by the AGM-158 JASSM. An AGM-129C conventional-warhead variant was also designated.

The missile was operated only by the United States Air Force and was carried exclusively by the B-52H, with up to six rounds on each of two external pylons and originally eight more internally on the Common Strategic Rotary Launcher. Plans to arm the B-1B were dropped after the Cold War.

On 10 December 1997 an AGM-129A carrying an inert payload struck two unoccupied trailers of a cosmic ray observatory at Dugway Proving Ground after a 3.5-hour test flight from the Utah Test and Training Range. On 30 August 2007 twelve ACMs were flown from Minot AFB to Barksdale AFB with W80-1 warheads still installed on six missiles; the weapons were unaccounted for over 36 hours.

Retirement was decided in March 2007 in favor of the AGM-86, citing reliability problems and maintenance costs, with the last missile destroyed in April 2012.