The US Navy's BGM-109 Tomahawk cruise missile; the problem weapon for arms control negotiators.

The US Navy's BGM-109 Tomahawk Cruise Missile

The Problem Weapon for Arms Control Negotiators

Under the terms of the INF (Intermediate Range Nuclear Forces) Treaty signed in December 1987 between the Soviet Union and the United States all land-based, medium-range, offensive guided missiles were to be eliminated in Europe. In NATO this has led to the destruction and decommissioning of all the American BGM-109G Tomahawk nuclear-tipped cruise missiles stationed in Western Europe. The numbers involved were 448 actual missiles and 122 mobile launchers. Not covered by the INF Treaty, however, are the naval versions of the BGM-109 family in service with the US Navy, which we propose to have a look at here.

The high subsonic speed BGM-109 Tomahawk cruise missile was designed to be launched from a variety of platforms, both land and sea-based (including submarines). A strategic air-launched version was also developed but was subsequently dropped when Boeing won the US Air Force Air-Launched Cruise Missile competition with its AGM-86. At the end of 1988 the US Navy already possessed over 26 surface vessels and 41 submarines equipped with the BGM-109 cruise missile system.

The Tomahawk Family

To ensure optimal coverage of the various targets it might be called upon to attack, the US Navy has developed the following four versions of the BGM-109 family. * BGM-109A Tomahawk Land Attack Missile - Nuclear (TLAM-N).

With a range of 2 500 km (1 350 nm), this version is suited as a strategic weapon for the attack of high-value land-based objectives. * BGM-109B Tomahawk Anti-ship Missile (TASM).

Equipped with a conventional 120 kg Bullpup warhead and with a range of around 460 km (230 nm), this version was put into service by the US Navy to complement its carrier-based ground attack planes. It is designed for the attack of enemy surface targets heavily defended against aerial attacks. Its performance is about equivalent to that of the latest Soviet naval cruise missiles. * BGM-109C Tomahawk Land Attack Missile-Conventional (TLAM-C).

Armed in the same way as the BGM-109B, but with a range of 1 290 km (700 nm), the TLAM-C is designed for the destruction of shore-based naval installations, surface ships and submarines lying in harbour as well as other high-value and well-defended land or shore-based objectives. * BGM-109D Tomahawk Land Attack Missile-Dispenser (TLAM-D).

With a penetration range of 1 290 km (700 nm) the TLAM-D is equipped with a dispenser warhead containing 166 BLU-97/B combined effects munition bomblets (shaped-charge, fragmentation and incendiary). It is intended for the attack of air bases and the suppression of enemy air defence systems.

TERCOM and DSMAC 

The anti-ship BGM-109B uses inertial navigation coupled to a midcourse radar altimeter and an active radar for terminal guidance. Target data is inputted before launch and the radar altimeter allows the missile to follow a sea-skimming path underneath the enemy's radar coverage. Once arrived in the target zone, the Tomahawk climbs to a sufficient height to enable, the active radar homing head to acquire the target and lock on. In its terminal phase the missile approaches the target either in level flight or in a pop-up attack profile followed by a steep dive.

The land target attack BGM-109C/D Tomahawk utilizes terrain comparison-aided inertial guidance with digital scene-matching terminal guidance. In other terms, the missile flies along a predetermined route and, at regular intervals, its TERCOM (TERrain COntour Matching) system compares the area actually overflown with a matrix of the terrain contours entered before launch to correct possible deviations. This combination of inertial guidance and scene-matching provides an accuracy of plus or minus 200 metres. For the destruction of point targets such as aircraft shelters and command posts, where accuracies of only a few metres are required, the BGM-109C has an additional installation for terminal phase guidance. This electro-optical system is called DSMAC (Digital Scene Matching Area Correlator) and it compares the image of the target area obtained by an infrared sensor in the missile's nose with a thermal image of the target under attack stored in the onboard computer before launch.

MDD Theater Mission Planning System

As seen earlier, target and flight path data are fed into the missile's computer before launch. This is done with cassettes that are prepared by a Theater Mission Planning System (TMPS) developed and manufactured by McDonnell Douglas. The TMPS gives the mission planning officer access to the various data files (including weather, TERCOM matrix data, etc.), thus enabling him to simulate a variety of Tomahawk missions so as to evaluate and eventually programme the optimal approach routes and attack profiles. In addition reconnaissance photos in the form of digital reference images can be processed with the aid of a Rapid Strike Planning System (RSPS) to serve as the basis for terminal guidance with the DSMAC guidance system. Both the TMPS and RSPS are on issue to US naval forces at home, in Western Europe and in the Pacific.

Dual-Source Competitive Contracts

In order to ensure maximum production and hence availability of Tomahawk missiles with the limited financial means at its disposal the US Navy chose a second-source manufacturer as long ago as December 1984. The competitor to General Dynamics' Convair Division selected as second-source supplier of the Tomahawk guidance system was McDonnell Douglas' Astronauties Company. These two companies are now competing within the limits of the FY 89 appropriation for the production contract covering the manufacture of the currently authorized batch of BGM-109.

Raising the Nuclear Threshold

With its family of BGM-109s the US Navy possesses a highly flexible weapon system whose wide operational capabilities have opened up totally new offensive capabilities. Some specialists maintain that the deployment of the Tomahawk is an additional deterrent effect to utilization of nuclear weapons. They point out in particular that the putting into service of the BGM-109 onboard US Navy surface ships and submarines gives the US Navy the means of reacting with measured response to any given threat worldwide and at any time.

PHOTO : A submarine-launched Tomahawk breaks the surface of the water under the power of its

PHOTO : booster motor. On burn-out, propulsion is taken over by a turbine engine.

PHOTO : After a stealthy terrain-following penetration flight, the Tomahawk pops up to take a

PHOTO : steep dive on its prey.

PHOTO : By the mid-1990s, the US navy will have a total of 191 attack platforms (100 submarines

PHOTO : and 91 surface ships) capable of launching the BGM-109 cruise missile.