The Tomahawk Land Attack Missile (TLAM) is an all-weather, long range, subsonic cruise missile used for land attack warfare, launched from U. S. Navy surface ships and U.S. Navy and Royal Navy submarines. Tomahawk cruise missiles are designed to fly at extremely low altitudes at high subsonic speeds, and are piloted over an evasive route by several mission tailored guidance systems.
In 1986, the designations were changed. Before that, different launch environment options were designated by suffix letters.
After the change, the first letters indicate the launch environment, RGM being the surface ship-launched, while UGM being the submarine-launched version.
The Tomahawk Block II, designated R/UGM-109C, also called TLAM-C (Tomahawk Land-Attack Missile - Conventional) is a conventionally-armed (same WDU-25/B warhead as -109B TASM) missile for long-range strikes against high-value targets. It uses the same INS/TERCOM suite as the -109A TLAM-N for mid-course guidance. For higher accuracy in the terminal phase of the flight, it uses an AN/DXQ-1 DSMAC (Digital Scene Matching Area Correlation) system, because the conventional warhead requires higher precision to be effective. DSMAC is an electro-optical sensor system which takes images from the ground below the missile and compares these to reference images stored in the on-board computer.
The Tomahawk Block IIB is designated R/UGM-109D, also called TLAM-D (Tomahawk Land-Attack Missile - Dispenser). It is similar to the TLAM-C (also using the TAINS/DSMAC guidance package), but in place of the unitary WDU-25/B warhead, it uses a warhead section with 166 BLU-97/B CEB (Combined Effects Bomblet) submunitions. The BLU-97/Bs can be dispensed in partial packages to attack several targets in one mission.
Block III has a significantly upgraded guidance unit, incorporating a GPS receiver to assist the TAINS system, and the improved DSMAC 2A which uses a wider imagery range and more scenes for the final fix. The Block III missiles were also upgraded with an improved F107-WR-402 engine with higher thrust and lower fuel consumption. The RGM/UGM-109C Block III also uses an improved WDU-36/B warhead which is smaller (thereby increasing fuel space) and lighter than the WDU-25/B but offers the same effect. The new warhead significantly increases the range of the Block III TLAM-C missile.
The original TLAM-C Block II had only one mode of final approach, it always flew straight into the side of the target. Early in the development program, however, the BGM-109C software was upgraded to Block IIA. This allows pre-launch selection of two additional attack modes. The first of these is a pop-up/terminal-dive maneuver, and the second is known as PWD (Programmed Warhead Detonation). Using PWD, the WDU-25/B warhead is detonated while the missile is flying directly over the target, making it especially effective against targets behind a protective shielding like a revetment.
The R/UGM-109E is called Tactical Tomahawk, it is aimed to cost significantly less (about one half) per production round than an up-to-date TLAM-C/D. Therefore a cheaper engine is used and the structure is lighter. The originally planned engine was the TBIP's J402-CA-401 turbojet, but this was changed during development to a Williams F415-WR-400/402 turbofan, causing a significant delay in the time schedule. Because of the lighter structure (which includes reducing the number of tailfins from four to three), the UGM-109E is unsuitable for launch from torpedo tubes, but can still be used from SSNs equipped with vertical launch systems. The RGM/UGM-109E also features a number of significant operational improvements. The missile can be reprogrammed in flight via an UHF satellite link to divert to any one of 15 pre-programmed alternate targets or to an arbitrary location defined by GPS coordinates. It can also loiter over the target area for some time while transmitting imagery from its on-board TV camera via the satellite link. The image can be used to assess battle damage and/or to retarget the missile.