Once the UGM-109 has reached a safe distance from the submarine, its rocket booster ignites underwater to power it airborne.

The canister remains in the vertical-launch or torpedo tube, while the missile is ejected. In both cases, a Tomahawk launches “wet”, unlike most anti-ship missiles. TTL canisters are used to launch Tomahawk missiles from a submarine’s torpedo tubes, which is Britain’s preferred method. CLS canisters launch UGM-109s from vertical launch tubes installed on many of America’s Los Angeles Class (SSN 719 on), all Virginia Class, and all SSGN Ohio Class submarines. UGM-109 “all-up-round” storage and interface canisters come in 2 types: CLS and TTL. Submarine-launched UGM-109 missiles are more expensive than their ship launched RGM-109 VLS counterparts, because the submarines’ launch mechanism is more involved and more strenuous. The missile also has a 2-way UHF SATCOM datalink that allows the missile to be redirected in flight, or commanded to loiter over an area and wait for instructions from a Fleet HQ’s Maritime Operations Center.

Mission planning has been cut from 80 hours to just 1 hour, which makes a big difference to combat usage. Block IV reportedly increases missile range to 900 nautical miles, but it only uses the unitary warhead. The xGM-109E Tomahawk Block IV achieved Initial Operating Capability in 2004, and current Pentagon plans will end purchases in 2015. Unfortunately, mission planning requires 80 hours of work. The Tomahawk Block III has a 750 nautical mile range. The xGM-109C/D Block III missiles will serve in the US Navy until FY 2020, and can be fitted with either a 1,000 pound unitary conventional warhead (xGM-109C), or a conventional submunitions warhead with hundreds of smaller bomblets (xGM-109D). CEP is often described as being about 10 meters. Once on target the missile can fly a direct horizontal attack mode, trigger preprogrammed detonation above the target, or use a pop-up and dive maneuver. The missile typically flies at 50 – 100 feet above ground using terrain-following radar, and navigates to its targets using a combination of GPS/INS, computer matching of the land’s radar-mapped contours to the missile’s internal maps (TERCOM), and final matching of the target scene (DSMAC). The USA has bought more than 4,000 over the years, and March 2011 saw the 2,000th GM-109 Tomahawk fired in combat, from USS Barry. Tomahawk missiles have become the US Navy’s major land strike missile.

Tomahawk cruise missile