BGM-109 Tomahawk cruise missiles are U.S. designed to be launched from ships and submarines; the submarine version is the UGM-109. A ground-launch version existed, but was destroyed as part of bilateral arms reduction. The weapons have gone through a number of generations of airframe, guidance, and warhead, and are now a mature system, proven in combat, that still finds room for improvements.
All versions fly at low altitude; while not formally stealthy, their relatively small size, and their closeness to the ground, make them hard radar targets. Their speed is in the high subsonic range (550 mph (880 km/h)). While a formal circular error probability has not been specified, they are considered accurate to precision.
They are 20.4 inches/520mm in diameter and 21 feet/6.2 meters long, with a takeoff weight of varying with model, but in the 2600 pound/1400 kg range.
Block I and II
Initially, the weapon used a combination of inertial navigation and terrain contour mapping, the latter a low-altitude radar technique that literally compares the ground being overflown with a digital map. Terminal guidance was provided by an optical image mapping system, Digital Scene-Mapping Area Correlator (DSMAC). The first versions were intended for two missions no longer assigned to Tomahawks: land attack with a W80 nuclear warhead BGM/RGM/UGM-109A (TLAM-N) and a long range anti-shipping missile BGM/RGM/UGM-109B (TASM) with inertial midcourse guidance and an active radar search in the terminal phase.
These were remanufactured into TLAM-C variants with a 1000 pound conventional explosive warhead, and TLAM-D carrying 166 BLU-97 combined effects cluster submunitions. They had an approxiately 300 mile range.
Guidance enhancements in this version added Global Positioning System (GPS) satellite navigation, as operational experience showed that terrain contour mapping was not always reliable over desert, and required prior surveys of the target area. The warhead uses an insensitive high explosive, PBXN-107, which could achieve the same effects of the earlier, heavier warheads. Reducing the warhead size allowed extending the range to approximately 700 miles.
The most recent version, also called "Tactical Tomahawk", is vastly more capable in a dynamic battlefield, as it has a two-way datalink that can be used for battle damage assessment, and changing targets in flight. They were used, along with Block III versions, in the March 2011 attack on Libya.
A current contract, running through 2011, calls for the manufacture of 2,135 missiles, 65 of which will go to the United Kingdom. While this is a $1.6 billion contract, the per-missile cost of the Block IV is lower than the earlier versions. The improved Joint Multi-Effects Warhead System (JMEWS) was tested successfully in October 2010, and will add a hard target penetrator capability. 
BGM-109 surface launch version
Two classes of surface warships, the Ticonderoga-class cruisers and Burke-class destroyers use the vertical launch system (VLS) with hot launch, usually populated primarily with surface-to-air missiles, but capable of loading large numbers of cruise missiles. The VLS are managed by the Mark 99 fire control system, a subsystem of the AEGIS battle management system.
Normally, a Ticonderoga-class carries 12 Tomahawks, but in a special mission in the Gulf War, USS San Jacinto (CG-56) loaded all 122 VLS tubes with Tomahawk, relied on sister ships for air defense, and was the principal land attack ship.
UGM-109 submarine launch version
UGM-109 versions cold launch from submarines, from VLS tubes on U.K. Astute-class, and U.S. submarines of the improved Los Angeles-class, Seawolf-class, and Virginia-class. A torpedo-tube-launched version is available, but the torpedo tubes cannot hold the longer and more recent versions.
- Unitary high explosive
- Cluster submunition
- Nuclear (W80 (nuclear weapon))
- Carbon filament fiber for temporarily disabling electrical power grids
- "Tomahawk/Tactical Tomahawk", Deagel
- Raytheon (25 October 2010), "US Navy Tests New Warhead for Tomahawk Block IV Missile", Defence Talk