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AGM-69A SRAM being loaded into B-1B bomb bay
|Type||Nuclear air-to-surface missile|
|Used by||United States|
|Diameter||440 millimetres (17.5 in)|
|Warhead||W69 nuclear warhead|
|Engine||Lockheed SR75-LP-1 two-pulse solid-fueled rocket|
|200 kilometres (110 nmi)|
|General Precision/Kearfott KT-76|
|Accuracy||430 metres (1,400 ft)|
The requirement for the weapon was issued by the Strategic Air Command of the USAF in 1964, and the resultant AGM-69A SRAM entered service in 1972. It was carried by the B-52, the FB-111A, and, for a very short period starting in 1986, by the B-1Bs based at Dyess AFB in Texas. SRAMs were also carried by the B-1Bs based at Ellsworth AFB in South Dakota, Grand Forks AFB in North Dakota, and McConnell AFB in Kansas up until late 1993.
SRAM had an inertial navigation system as well as a radar altimeter which enabled the missile to be launched in either a semi-ballistic or terrain-following flight path. The SRAM was also capable of performing one "major maneuver" during its flight which gave the missile the capability of reversing its course and attacking targets that were behind it, sometimes called an "over-the-shoulder" launch. The missile had a Circular Error Probable (CEP) of about 430 metres (1,400 ft) and a maximum range of 200 kilometres (110 nmi). The SRAM used a single W69 nuclear warhead with a variable yield of 17 kilotons as a fission weapon, or 210 kilotons as a fusion weapon with Tritium boost enabled. The aircrew could turn a switch on the Class III command to select the destructive yield required.
The SRAM missile was completely coated with 2 cm of soft rubber, used to absorb radar energy and also dissipate heat during flight. The three fins on the tail were made of a phenolic material, also designed to minimize any reflected radar energy. All electronics, wiring, and several safety devices were routed along the top of the missile, inside a raceway.
On the B-52, SRAMs were carried externally on 2 wing pylons (6 missiles on each pylon) and internally on an eight-round rotary launcher mounted in the bomb bay; maximum loadout was 20 missiles. The B-1B could carry 8 missiles on up to three rotary launchers (one in each of its three stores bays) for a maximum loadout of 24 missiles. The FB-111A could carry two missiles internally and four more missiles under the aircraft's swing-wing. On the FB-111A, the externally-mounted missiles required the addition of a tailcone to reduce aerodynamic drag during supersonic flight. Upon rocket motor ignition, this tailcone was blown away by the exhaust plume.
About 1,500 missiles were built at a cost of about $592,000 each by the time production ended in 1975. The Boeing Company sub-contracted with the Lockheed Propulsion Company for the propellants, which subsequently closed with the end of the SRAM program.
An upgraded AGM-69B was proposed in the late 1970s, with an upgraded motor to be built by Thiokol and a W80 warhead, but it was cancelled (along with the B-1A) in 1978. Various plans for alternative guidance schemes, including an anti-radar seeker for use against air defense installations and even a possible air-to-air missile version, came to nothing.
A new weapon, the AGM-131 SRAM II, began development in 1981, intended to arm the resurrected B-1B, but it was cancelled in 1991 by then president George H. W. Bush along with most of the U.S. Strategic Modernization effort (including Peacekeeper Mobile (Rail) Garrison, Small ICBM and Minuteman III modernization) in an effort by the U.S. to ease nuclear pressure on the disintegrating Soviet Union.
The AGM-69A was finally retired in 1993 over growing concerns about the safety of its warhead and rocket motor. With the end of the Cold War it is unlikely to be replaced in the immediate future. There were serious concerns about the solid rocket motor, when several motors suffered cracking of the propellant, thought to occur due to the hot/cold cycling year after year. Cracks in the propellant could cause catastrophic failure once ignited.
The SRAM was effectively replaced by the AGM-86 cruise missile, which has longer range, though easier to intercept.
The number of AGM-69 missiles in service, by year:
- 1972 - 227
- 1973 - 651
- 1974 - 1149
- 1975 - 1451
- 1976 - 1431
- 1977 - 1415
- 1978 - 1408
- 1979 - 1396
- 1980 - 1383
- 1981 - 1374
- 1982 - 1332
- 1983 - 1327
- 1984 - 1309
- 1985 - 1309
- 1986 - 1128
- 1987 - 1125
- 1988 - 1138
- 1989 - 1120
- 1990 - 1048 (deactivated by President George H.W. Bush)
- Length: 4.8 metres (190 in) with tail fairing, 4.3 metres (168 in) without tail fairing
- Diameter: 440 millimetres (17.5 in).
- Wing span: 760 millimetres (30 in).
- Launch weight: 1,010 kilograms (2,230 lb).
- Maximum speed: Mach 3.5
- Maximum range: 56–169 kilometres (35–105 mi) depending on flight profile
- Powerplant: 1 × Lockheed SR75-LP-1 two stage solid-fuel rocket motor
- Guidance: General Precision/Kearfott KT-76 IMU and Stewart-Warner radar altimeter
- CEP: 430 metres (1,400 ft)
- Warhead: W69 thermonuclear (170-200 kt of TNT)
- Gunston, Bill (1979). Illustrated Encyclopedia of the World's Rockets & Missiles. London: Salamander Books. ISBN 0-517-26870-1