RIM-116 Rolling Airframe Missile

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Replacing the Phalanx close-in weapons system, based on 20mm autocannon, the RIM-116 Rolling Airframe Missile (RAM) is a final anti-air warfare defense against anti-shipping missiles of supersonic speed. While the Phalanx was effective against subsonic missiles such as the SS-N-2 STYX, it had insufficient range and speed for engaging faster, deadlier threats such as the Russian SS-N-22 SUNBURN.

This is the missile component of the joint U.S./German MK 31 Guided Missile Weapon System, and is launched from MK 49 box-launchers holding 21 missiles. [1]


The first production missile, operational in 1993, was a chimera built from components of several other missiles: the rocket motor of the MIM-72 Chaparral, the warhead of the AIM-9 Sidewinder and the infrared seeker of the FIM-92 Stinger. Additional guidance modes characterize sthe second version, which began operational deployment in 2004.

RIM-116A: RF and IR version

The first production RAM, whose delivery to the fleet began in 1993, 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.

RIM-116B RAM Block I: new guidance modes

This version, sometimes called RAM II, differs principally in having additional guidance modes. It became operational in 2004. The first, "IR all the way", is used against threats that do not radiate RF that the seeker can detect. The second, IR Dual Mode Enable, is the opposite of the IR-after-radar of the first model. In IRDM, the midcourse guidance is IR, but can switch to terminal passive radar homing.

Block II: increased range and maneuvering

Scheduled to start flight test in 2008 and be operational in 2011, this version has a more powerful engine, and more and larger aerodynamic control fins.


The U.S. Navy plans to deploy it on:

  • Amphibious Assault Ships (LHA/LHD)
  • Carriers (CV/CVN)
  • Dock Landing Ships (LSD)
  • Littoral Combat Ship (LCS)

Destroyers and cruisers with the Phalanx close-in weapons system will retain it, as the final layer after the RIM-156 Standard SM-2, which can engage targets at least 130 nm/240 km away. The RIM-162 ESSM (Evolved Sea Sparrow Missile), with a range of 27+ nm/50+ km, forms the next band.

General information

  • Contractor: Raytheon[2]
  • Length 2.82 m (9 ft 3 in) [1]
  • Wingspan 43.8 cm (17.25 in)
  • Diameter 12.7 cm (5 in)
  • Weight 73 kg (162 lb)
  • Speed Mach 2+
  • Range 9 km (5 nm)
  • Propulsion MK 112 MOD 1 solid-fueled rocket
  • Warhead 9.1 kg (20 lb) WDU-17/B blast-fragmentation