September 30, 2010
To implement the U.S.-Russian "New START" arms control agreement, Washington is likely to "inactivate" one-sixth of its capacity to launch nuclear weapons from submarines, according to defense officials (see
GSN, Sept. 27).
The alteration, if performed, would involve rendering unusable four ballistic missile launch tubes on each of 14 Trident submarines. Today the vessels
feature 24 active launch tubes, each containing a single D-5 ballistic missile. The change would bring that number down to 20 missiles per boat.
"Nothing has been decided because the final force structure [under the treaty] has not been chosen," said one Defense Department official, who was not authorized to speak publicly about the issue and requested anonymity in this article. "But it is about a 98 percent certainty that that's what we'll do."
Though technical details remain uncertain regarding how the modifications would be made, U.S. officials anticipate the changes would be verifiable by Russian arms control inspectors.
The partial inactivation of launch tubes would also almost certainly be reversible, allowing Washington to meet treaty caps but retain some flexibility in how its smaller nuclear arsenal is arrayed in the future, defense sources said.
U.S. President Barack Obama and Russian President Dmitry Medvedev signed the New START agreement in April. Now pending before U.S. and Russian lawmakers for ratification, it limits each side to 1,550 deployed warheads aboard 700 strategic delivery vehicles, such as aircraft, submarine-launched ballistic missiles and ground-based ICBMs. Another 100 delivery platforms could be kept in reserve.
Once the treaty enters into force, the Obama administration plans to "deploy no more than 240 Trident 2 SLBMs at any one time," James Miller, the principal deputy defense undersecretary for policy, told a Senate committee in July.
Just 12 of today's 14 Trident submarines are operational, with two boats in overhaul at any given time. Warheads or missiles in vessels undergoing the periodic maintenance are not counted under New START limits.
The Defense Department currently fields 288 Trident D-5 missiles, filling each of the 24 launch tubes aboard 12 deployed submarines. As New START is implemented and the launch-tube modifications are made, the Navy would be able to reduce to the Pentagon objective of 240 missiles using this math: 20 missiles multiplied by 12 operational vessels.
The Pentagon's
Nuclear Posture Review -- a major assessment of strategy and forces released in April -- stated that the Navy will continue to field 14 total ballistic-missile submarines for the time being, but might reduce to 12 such boats before the end of the decade. With two of those typically in overhaul, just 10 would be regarded as operational day to day.
If the Defense Department goes forward with trimming its Trident submarine fleet in the coming years, it would have the option of reversing the launch-tube inactivation and renewing its capacity for the remaining 10 operational vessels to carry 24 missiles apiece, maintaining the level of 240 missiles fielded across the fleet, officials said.
The launch-tube measure could thus be seen as a "bridge" to the probable reduction in the quantity of ballistic-missile submarines by the end of the decade, said Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists. "Otherwise, they'd have to wait till the end of the decade to reduce missiles out there," he said in an interview this week.
However, some observers believe it might be politically difficult for the Navy to return to loading 24 nuclear missiles per vessel later in the decade. After having maintained nuclear deterrence for several years by sailing with just 20 weapons on each submarine, it could appear that an additional four would be unnecessary, the argument goes.
"If they go to sea with only 20, that would cause people to re-evaluate the requirements for the D-5 life-extension program, which assumes 24 missiles," said one industry analyst, referring to the Navy's current effort to field 108 updated versions of the submarine-based weapon. "So if you drop four missiles per boat, then you could reduce the buy by 48 missiles."
The Navy plans to introduce the life-extension version of the D-5 missile into the fleet in three years. The modified arms will include newly produced rocket motors, remanufactured flight hardware and modern guidance instruments.
A decision to reduce the number of missiles on Trident vessels "would also say that the option of 24 tubes per boat on the new submarine design doesn't look like it would be valid any more," said the analyst, who asked not to be named in discussing sensitive fielding options.
The Navy's next-generation ballistic missile submarine, called the SSBN(X), could have as few as 16 launch tubes or as many as 24, with design details expected to go before a top-level Pentagon review board for decision in November, defense sources said.
The Nuclear Posture Review asserted that a reduction to 10 operational submarines "will not affect the number of deployed nuclear warheads" on the vessels. The Ohio-class submarines currently carry a total 1,152 warheads and, once the New START reductions are taken, they would likely carry just under 1,100, Kristensen estimated.
If the Pentagon declines to reactivate the four launch tubes once the submarine fleet shrinks to 10 deployed boats, the Navy could retain the same number of warheads across its remaining 200 missiles by arming them with five to six warheads apiece, instead of today's average of four, Kristensen said.
Taking policy considerations into account, a reversible inactivation of the launch tubes also offers Obama administration leaders a "hedge" against any resurgence in Russian strategic forces or some other strategic surprise, officials said. The New START
agreement includes a clause that allows either side to withdraw if it determines that "extraordinary events" have jeopardized its national security.
The nation has seven years to take reductions in its force structure, following the accord's entry into force.
Defense Department engineers are just now beginning to assess how they might suspend the usability of four launch tubes on each boat, according to Pentagon sources.
Under one engineering approach, the Navy might simply remove the gas pressure system that allows a ballistic missile to be ejected by "cold launch," before its rocket motors kick in. Another method could involve inserting a narrow sleeve into each tube that would make it impossible for a D-5 missile to fit inside.
A third option might be to replace each of the four D-5s with a "ballast can," a 15-foot weight that a submarine could carry for stability when a missile is not in its tube, according to sources.
"That's what the Navy has to figure out," the Pentagon official said.
Beyond the submarine leg of the U.S. nuclear triad, Washington under New START expects to "retain up to 420 of the current 450 Minuteman 3 ICBMs, each with a single warhead," Miller told the Senate Armed Services Committee on July 20. "And we plan to retain up to 60 nuclear-capable B-2A and B-52H heavy bombers, while converting remaining nuclear-capable B-1B bombers and some B-52 bombers as well to a conventional-only capability."
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