Tomahawk Part 1

Of all the weapons that have entered service over the last 50 years, none have had a greater impact on naval warfare than the Tomahawk cruise missile. This weapon has given destroyers and submarines the ability to strike targets far inland, a capability that was previously the exclusive preserve of the carriers. This dispersion of strike power has proved vital to the surface and subsurface navies in the post-Cold War world, and has given the President new tools for projecting American power.

Iowa launches a Tomahawk

Tomahawk originated in the early 1970s, shortly after the signing of the Strategic Arms Limitation Treaty (SALT I), which didn't cover submarine-launched cruise missiles. The basic idea of such a missile wasn't new. The JB-2 Loon had been test-fired from a couple of submarines in the years after WWII, and the US had followed it with Regulus, which was fitted to five submarines, which conducted deterrent patrols in the Pacific from 1959 to 1964. However, Regulus was large enough that even its specialized submarines could only carry 2-5 missiles and it had to be launched from the surface, so it was rapidly phased out and replaced by Polaris. But in the aftermath of SALT I, which limited most types of nuclear weapons but not cruise missiles, the time seemed ripe to try again. The new weapon would have to fit into a standard 21" torpedo tube and be launched from underwater, giving the fleet's attack submarines a strategic strike capability against the Soviet Union.

A Tomahawk breaks the surface after being launched from a torpedo tube

The program moved quickly, with General Dynamics and LTV being awarded contracts for the BGM-109 and BGM-110 respectively. Guidance and engine development were undertaken independently, with cooperation from the Air Force, which was also seeking to develop a new cruise missile for its bombers. In 1977, General Dynamics won the competition, which by this point had broadened to include not only the nuclear land-attack missile, subsequently called TLAM-N (Tomahawk Land Attack Missile-Nuclear), but also an anti-ship version (TASM, Tomahawk Anti-Ship Missile) and a conventional land-attack version (TLAM-C). Also added to the program were versions of the missile designed to be launched from surface ships, and from vertical tubes that would be fitted to future submarines. By late 1983, TASM entered service onboard the submarine Atlanta, followed by TLAM-N the next June. Surface ships followed swiftly, with the first operational missiles aboard the battleship New Jersey. Tomahawk was a key driver of the reactivation of the Iowa class battleships, with Iowa following her sister into service in 1984. The conventional missiles took a bit longer to reach operational status, but both unitary warhead and submunition variants were in service by 1988. They were joined by the BGM-109G GLCM, a ground-launched nuclear variant that bolstered NATO's intermediate-range nuclear forces from 1983.¹

All of these missiles were built around the same basic body and engine, an airframe 18' 3" long and 20.3" in diameter with pop-out wings and a small turbofan engine providing 600-700 lb of thrust. The whole missile weighs somewhere between 2,700 and 3,000 lb, and is boosted into the air by a rocket that is then discarded. The ship and submarine-launched versions of a given type are very similar, differing primarily in their launching mechanism. The submarine-launched versions can be fired out of a torpedo tube, with the missile being ejected and then the booster fired to drive it out of the sea and into the air. Most submarines built since the mid-80s have also been fitted with vertical tubes to give extra Tomahawk capacity. Most attack submarines carry 12, while four of the Ohio class ballistic missile submarines have been converted to fire 7 Tomahawks each from 22 of their missile tubes.

A Tomahawk emerges from the VLS of the destroyer Sterett

The vast majority of surface ship Tomahawks are also launched vertically, using the Mk 41 Vertical Launching System that equips all modern American cruisers and destroyers. The Mk 41 provides unmatched versatility, allowing tradeoffs to be made between land-attack missions, air-defense in the form of Standard and ESSM, and anti-submarine warfare with VLASROC. But VLS didn't go to sea until the late 80s, so another means was needed to give surface ships an interim capability with Tomahawk. Initial plans were for an open rack similar to that used for Harpoon, but the 1975 fire on the cruiser Belknap increased interest in damage resistance, and an Armored Box Launcher (ABL) was developed. It would protect a quartet of horizontally-stored missiles with an inch or so of armor, then open up for launch. The first weapons would go to sea on the destroyer Merrill, which carried two ABLs, followed by the battleship New Jersey, which was fitted with eight when she was reactivated in the 1980s. Her three sisters were also fitted with a heavy Tomahawk battery, and these weapons formed an important part of the rationale for their last stint in service.

One of Iowa's ABLs, open but not elevated

The TLAM-N was equipped with a W80 nuclear warhead, which has an adjustable yield of either 5 kt or 150 kt.² After launch, it was inertially guided until it made landfall, where the inertial system was updated by a system called Terrain Contour Matching or TERCOM. This involved a series of digitized elevation maps of specific areas along the missile's trajectory. A radar altimeter would read the ground below the missile, and use this data to figure out where in the terrain map it was. The first maps had large cells, to make it easy for the missile to locate itself, and later ones strung along the flightpath were smaller, giving greater accuracy, with the CEP³ estimated at 50m even at the missile's maximum range of 1,350 nm.

How TERMCOM works

The TLAM-N had immense strategic implications. Before it entered service, only the carriers had the capability to launch nuclear strikes from the sea, and the Soviets had dedicated a lot of resources to tracking and sinking the carriers before they could do so. One cornerstone of this was their ocean surveillance network, which was designed to track a dozen or so vessels at a time. Tomahawk gave any ship or submarine the potential to add to the nuclear striking force, completely overwhelming the Soviet surveillance system. It was not a particularly popular weapon, as any nuclear-capable system had to be guarded at all times as if it was carrying nuclear warheads, increasing the demand on the ship's crews and restricting operations. Ultimately, the TLAM-Ns were withdrawn from shipboard inventories in 1991, along with all other sea-based nuclear weapons except for those aboard SSBNs, but they remained in the US stockpile for another two decades before being retired, and the reintroduction of a nuclear-tipped Tomahawk has been discussed in recent years.

The original TLAM-N guidance set

While the nuclear mission was the impetus to the Tomahawk, it was as a conventional weapon that the Tomahawk has changed the face of naval warfare. And while the land-attack models have gotten all of the headlines over the years, the first of the conventional models was the Tomahawk anti-ship missile. We'll look at it next time.