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Raytheon (General Dynamics) RIM-116 RAM

The RIM-116 RAM is a joint U.S./German lightweight ship-borne self-defense system for use against anti-ship cruise missiles.

In the mid-1970s the U.S. Navy ships had no adequate defense against low-flying cruise missiles. A program to develop a 5-inch missile was begun in 1975, and in July 1976 an agreement was signed with Germany for joint development of the RIM-116 weapon system. The missile was later called RAM (Rolling Airframe Missile), because it was spinning during flight. To save costs, the RAM was designed to use several existing components, including the rocket motor of the MIM-72 Chaparral, the warhead of the AIM-9 Sidewinder and the IR seeker of the FIM-92 Stinger. The XRIM-116A first flew in 1978, and a full-scale development contract was awarded to General Dynamics in June 1979. Experimental training rounds were designated XRTM-116A at that time. Numerous development problems were encountered during the 1980s, and although several successful test intercepts were made during 1982/83, it took until 1987 that RAM was finally approved for continued development to production status. After operational evaluation in early 1990, the RIM-116A (also known as RAM Block 0) was finally declared ready for operational service with the U.S. Navy in 1992.

Photo: U.S. Navy

The RIM-116A is the missile component of the MK 31 Guided Missile Weapon System, and is launched from MK 49 box-launchers holding 21 missiles. The production RAM is powered by a MK 112 solid-propellant rocket motor. After launch, the passive RF seeker homes on the incoming cruise missile's radar emission. Because of the rolling airframe, only two RF antennas and two forward steering fins are necessary instead of the usual four in a non-spinning missile. When the missile is close enough to the target or the latter stops its emitter, it switches to IR terminal homing. The 9.1 kg (20 lb) WDU-17/B blast-fragmentation warhead is triggered by a laser proximity fuze. The RTM-116A is the RAM Block 0 training round.

Photos: U.S. Navy

In 1993, the development of the upgraded RIM-116B RAM Block I (sometimes called RAM II) was initiated. The RIM-116B has new "IR-all-the-way homing" guidance modes in addition to the RF/IR of the RIM-116A. The "IR only" mode is used against threats which do not emit detectable RF radiation. The second new option is called IRDM (IR Dual Mode Enable). In that mode, the RAM is launched with IR guidance enabled, but can switch to passive radar homing when the target's radiation becomes adequate to guide on. For IR-all-the-way guidance, the RIM-116B's IR seeker must be able to search and lock on the target after launch. After operational testing in early 1999, the RAM Block I was declared suitable for service, and full-scale production was approved in January 2000. The unarmed Block I training round is designated RTM-116B.

The RAM Block I system is planned for installation on many U.S. Navy surface ships, including LSD, LHD, LPD and CVN classes. About 1000 RIM-116A missiles (including 400 for the German Navy) have been built through 1999, and production has since switched to the RIM-116B version.

In the 2005/06 time frame, development of the significantly improved RAM Block 2 version was begun. Block 2 features four instead of two movable canards, 40% larger canards, and a new boost/sustain rocket motor of 14.6 cm (5.75 in) diameter. The changes will significantly enhance the missile's kinematic envelope in terms of range and manoeuverability. The first flight tests are planned for 2008, and the initial deployment for 2011.


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

Data for RIM-116A/B:

Length2.82 m (9 ft 3 in)
Wingspan43.8 cm (17.25 in)
Diameter12.7 cm (5 in)
Weight73 kg (162 lb)
SpeedMach 2+
Range9 km (5 nm)
PropulsionMK 112 MOD 1 solid-fueled rocket
Warhead9.1 kg (20 lb) WDU-17/B blast-fragmentation

Main Sources

[1] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983
[2] Norman Friedman: "World Naval Weapons Systems, 1997/98", Naval Institute Press, 1997
[3] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[4] Hajime Ozu: "Missile 2000 - Reference Guide to World Missile Systems", Shinkigensha, 2000
[5] Bernard Blake (ed.): "Jane's Weapon Systems 1987-88", Jane's, 1988
[6] John Pike: Website

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Last Updated: 25 November 2006