While controversy abounds in the Navy's attack submarine program, the Trident ballistic missile submarine force is being updated.1 However, several important issues are still to be resolved in that area.
Today the Trident submarine forcewhich contributes some 2,000 warheads or one-half of the warheads of the nation's strategic offensive forces-consists of 14 ballistic missile submarines (SSBN) that can carry 336 submarinelaunched ballistic missiles (SLBMs). All submarines will have the Trident II/D-5 missile that carries a multiple warhead of up to six W76 or W88 thermo-nuclear weapons.
The first eight Trident submarines of the Ohio (SSBN-726) class were originally armed with the Trident I/C-4 missile. Of those, four submarines (SSBN-726-729) are now undergoing conversion to combination Tomahawk cruise missile-special forces transport submarines (SSGN), and the second four (SSBN-730-733) are being rearmed with the D-5 missile. As this column was written only the USS Alabama (SSBN-731) still carried the C-4, which will shortly be phased out of the fleet. She will go to sea with the D-5 missile in 2006.
The Trident D-5 missiles come in two flavors: the Mk-4 reentry vehicle uses W76 warheads, each with an explosive force of about 100 kilotons, while the Mk-5 reentry vehicle carries W88 warheads, each with a yield estimated at 455 kilotons. The majority of the Trident missiles carry W76 warheads.
Improvements are being made to the D-5 missiles to assure their viability and a small number of additional missiles are being procured to support a robust testing program. The Navy is modernizing the Mk-4/W76 reentry vehicles with a new ground-burst fuze replacing the weapon's existing air-burst fuze. The first production units, designated Mk-4A/W76-1, are scheduled for delivery in September 2007. The new fuze will enhance the weapon's lethality and broaden the list of potential targets that can be attacked. An estimated 40% of the future stockpile of Mk-4/W76 reentry vehicles—approximately 800—will be updated by 2012.
Also, the Navy has proposed the enhanced effectiveness (E2) program to guide SLBM warheads with the accuracy level of the global positioning system (GPS)—less than 30 feet—further increasing types of targets that can be attacked with the W76 warhead. The program could apply to Trident D-5 missiles carrying a conventional warhead, if it is pursued. An SLBM with a conventional warhead has periodically been proposed for attacking long-distance, time-urgent targets. The concept was usually rejected because to an enemy ballistic missile warning system, there would be no way to differentiate an incoming conventional from a nuclear SLBM.
However, the Defense Science Board has now made such a recommendation in the context of arming the converted SSGNs with a conventional SLBM. Rear Admiral Charles B. Young, Director of Strategic Systems Programs, recently said that such a missile could deliver 1,250 pounds of conventional explosives to a range of 1,500 nautical miles. "Time of flight would be about 14 to 15 minutes... so if you have a time-critical target, that is a great capability."2 Young added that there was not yet a formal program to develop such a weapon.
Earlier the Navy looked into modifying the Army's ATACMS (Army Tactical Missile System) for use in the verticallaunch system (VLS) in attack submarines. ATACMS, a ballistic missile used by the U.S. Army and several foreign services, was proposed in the mid-1990s for submarine use with GPS guidance and a range of more than 150 nautical miles. At the time Rear Admiral Dennis A. Jones, Director of the Submarine Warfare Division, said that there is no reason why any weapon in the military inventory "cannot be shot submerged.... We are also exploring this option: a subsurface to air or a sub-surface to surface missile."3 According to Jones, the Navy had recently completed a feasibility study that showed the ATACMS could be launched from a standard attack submarine's VLS with only minor modifications being required.
However, the Navy, which launches only Tomahawk cruise missiles from the SSN vertical tubes, did not pursue the ATACMS and previous proposals to arm SSBNs with conventional missiles were also rejected. If the conventionalwarhead Trident is now pursued, it may arm Ohio-class SSBNs in addition to or instead of SSGNs, although the Navy is also considering a 32 1/2-inch diameter sea-launched intermediate range ballistic missile (SLIRBM).
While upgraded Trident nuclear SLBMs and possibly conventional Trident SLBMs are in the offing, the composition and manning of the Trident SSBN force is less clear. When the Cold War ended in December 1991, the Navy had 12 Trident missile submarines in commission and another six under construction. The last, the Louisiana (SSBN-743), had been started on 15 May 1991. Although the submarine community wanted to pursue the tentatively planned 24 Trident submarines, the administration of President George H.W. Bush halted the program at 18 units. Subsequently, under terms of the now-defunct strategic arms limitation agreements with Russia, the Trident SSBN force was reduced to 14 submarines.
These submarines are expected to have a service life of just over 40 years, meaning that the oldest SSBN should be retired about 2025. The Trident SSBNs were built at the rate of one per year. Navy long-range planning documents currently show a force of 14 SSBNs for at least the next 30 years.4 The same SSBN force level appears in both of the fleet structures recently presented to Congress-one for 260 ships and one for 325 ships.
To maintain the 14-ship SSBN force the Navy proposes to initiate the construction of a new SSBN(X) class beginning with the fiscal year 2023 program, and building one submarine per year indefinitely. This plan does not address two significant factors:
SSBN Manning. Today the Trident submarines operate with Blue and Gold crews that alternate operational deployments on a 112-day cycle that consists of a 77-day patrol followed by a 35-day refit period. Normally the refit begins with a two-day period when the submarine is turned over to the alternate crew making the next patrol and ends with five days underway for a combined-crew sea trial and refresher training period.
The fiscal year 2005 Defense Authorization Bill required the secretary of Defense to conduct a study—due in the spring of 2005—on whether the current practice of using alternating crews for SSBN patrols should be continued, modified, or terminated. The Navy performed the required study, called the "Single-Crew Study Report," which was forwarded to the Department of Defense on 19 July 2005.
The study is classified. However, sources indicate that the study recommends a continuation of the current twocrew policy.
SSBN Numbers. The 14-ship SSBN force was created by a combination of the number of submarines in train when the Cold War ended, and then-existing arms agreements. The nation's strategic nuclear forces also include 500 intercontinental ballistic missiles (ICBMs) with about 1,000 warheads, and 115 nuclearcapable strategic bombers that can carry an estimated 850 nuclear cruise missiles and 200 nuclear bombs.
Unquestionably, the SSBNs are the most survivable component of this force, and their long-time limitation of communications while submerged is being corrected.
Still, questions must be asked. First, what are the potential target nations for these weapons, especially in the context of the limited strategic missile/bomber threat to the United States. second, how many strategic nuclear weapons are needed to cover those targets. Finally, what should be the mix of strategic weapons. These and related questions must be asked in the context of current and probable U.S. military requirements for the war against terrorism, the current and probable funding levels for the Navy, and other issues.
The answers are not simple. But it seems increasingly obvious that answers derived at the end of the Cold War-almost 15 years ago-are unlikely to be valid today.
1 This column is based in part on Robert S. Norris and Hans M. Kristensen, "U.S. Nuclear Forces, 2005," Bulletin of the Atomic Scientists, January-February 2005, pp. 73-75.
2 Rear Adm. Young statement on 16 June 2005, quoted in Jefferson Morris, "Older Trident Missiles To be Phased Out By Fall, Admiral Says," Aerospace Daily & Defense Report, 17 June 2005.
3 Rear Adm. Jones address to the Naval Submarine League, Fort Myer, VA, 8 November 1995.
4 Department of the Navy, "An interim Report to Congress on Annual Long-Range Plan For The Construction of Naval Vessels For FY 2006," 23 March 2005, p. 4.