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The Navy is conducting flight tests of the Trident II submarine-launched ballistic missile. Some in the Congress have argued that certain of these tests--those involving the twelve-warhead version of the missile--could complicate future arms negotiations. Should the Congress limit tests of the twelve-warhead version? If so, how should they be limited? These issues merit prompt attention since the first test of the twelve-warhead version with a full complement of warheads is scheduled to occur within the next few weeks.
To aid the Congress in exploring the issue, this analysis by the Congressional Budget Office (CBO) examines the advantages and disadvantages of two options in the event the tests continue and one option in the event they are canceled. The study was requested by the Ranking Minority Member of the Senate Committee on Armed Services. In accordance with CBO's mandate to provide objective analysis, the study makes no recommendations.
Jeffrey A. Merkley of CBO's National Security Division prepared the
study, under the general supervision of Robert F. Hale and John D. Mayer,
Jr. The author also gratefully acknowledges the contributions of Marvin
M. Smith and Mark Dayton of CBO. Francis S. Pierce edited the manuscript,
and Rebecca J. Kees prepared it for publication.
Edward M. Gramlich
Acting Director
November 1987
SUMMARY
FLIGHT TESTS AND ARMS CONTROL
APPENDIX--Effects of Phantom Warheads on Capability of U.S. Strategic Ballistic Missile Force
The United States has several types of strategic nuclear weapons including bombers, sea-launched cruise missiles, intercontinental ballistic missiles (ICBMs), and submarine-launched ballistic missiles. To improve its submarine-launched ballistic missiles, the United States is developing the more accurate and more powerful Trident II missile to replace the current Trident I missile.
The flight-test program for the Trident II missile is the subject of a controversy: Should flight tests of one version of the missile--a version configured to carry twelve warheads--continue even if those tests might complicate negotiation of an agreement reducing strategic nuclear warheads?
The controversy has arisen from efforts to achieve the best results in two separate areas: weapon design and arms control. In designing and developing the Trident II, the Navy and the Administration have striven to obtain flexibility and to utilize the large carrying capacity or "payload" of the missile. Accordingly, the Navy has planned to develop and deploy two versions of the missile:
Flight-testing both versions of the Trident II would, however, potentially complicate one of the major tasks in negotiating an agreement reducing strategic warheads: determining how many warheads to credit to each type of strategic ballistic missile. Analysis of several strategies for crediting warheads to the Trident II suggests that, if further flight tests of the twelve-warhead version go forward, either the United States or the Soviet Union could feel disadvantaged. That would not preclude an arms agreement but could make negotiations more difficult. Despite testing already done to date, limiting further tests of the twelve-warhead version might avoid these complications.
PROCEED WITH TESTS OF TWELVE-WARHEAD VERSION: ADVANTAGES AND DISADVANTAGES
If flight tests of the twelve-warhead version of the Trident II proceed, the United States would have two basic strategies for crediting warheads to the Trident II under a limit on strategic warheads. The first would credit the Trident II with eight warheads while the second would credit it with twelve warheads.
One Strategy: Seek to Credit Trident II with Eight Warheads
Under this strategy, the United States would continue to test and deploy a mix of both versions of the Trident II; in arms negotiations, however, the United States would offer to cancel deployment of the twelve-warhead version but insist on crediting the Trident II with only eight warheads.
This strategy offers several advantages to the United States. Since the strategy imposes no limits on flight tests, it would not cause any delays in the development program for the Trident II. Also, in the absence of an agreement limiting strategic nuclear weapons, the United States would be able to deploy both versions of the Trident II, utilizing the large payload of the missile and maintaining the flexibility inherent in deploying both larger and smaller warheads. Furthermore, in the event of an agreement, crediting the Trident II with only eight warheads would deploy the permitted number of warheads on a larger number of missiles and hence a larger number of submarines, enhancing their survivability and improving U.S. confidence in deterrence.
The major drawback to this strategy is that the Soviet Union would probably strongly resist efforts to credit the Trident II with only eight warheads after a twelve-warhead version had been developed and fully tested. In an agreement reducing strategic weapons, each side would want to prevent the other from having the capability to deploy extra warheads surreptitiously or to "break out" of the agreement--that is, to withdraw from the treaty suddenly and increase quickly the number of warheads on deployed missiles. Under this U.S. strategy, however, the United States would have these capabilities: the Trident II would be credited with only eight warheads while having a fully developed capability to carry twelve warheads. Thus, the Soviet Union would almost certainly argue that the Trident II should be credited with twelve warheads.
The United States might eventually persuade the Soviet Union to credit the Trident II with only eight warheads. But the Soviet Union might seek other concessions, adding to the complexity of negotiations that are already difficult.
Another Strategy: Agree to Credit the Trident II with Twelve Warheads
If the United States proceeds to develop and flight-test the twelve-warhead version of the Trident II as well as the eight-warhead version, another strategy would have the United States deploy both versions but agree to credit the Trident II with twelve warheads under any future agreement limiting strategic nuclear weapons.
This strategy has some of the same advantages as the previous approach, leaving the current development program for the Trident II undisturbed and enabling the United States, in the absence of an agreement, to maintain flexibility by deploying both versions of the missile. In addition, since this strategy would credit the Trident II with the maximum number of warheads for which it was designed, the strategy should raise no objections from the Soviet Union.
Crediting the Trident II with twelve warheads would, however, lead to disadvantages for the United States. If the Trident II was credited with twelve rather than eight warheads, the United States could deploy fewer missiles under a sublimit on ballistic missile warheads. Under lower sublimits like the one currently proposed by the United States, deploying these missiles on Trident submarines could result in a fleet of missile-carrying submarines only one-fourth to one-third of the current number. The United States would therefore have to choose between the risk that this smaller fleet would be more vulnerable (the Soviet Union might devote more resources to attacking it through conventional means or through sabotage) and the cost of increasing the size of the fleet either by reducing the number of missiles each Trident can carry or by deploying a new class of smaller missile-carrying submarines.
Moreover, crediting the Trident II with twelve warheads would present a dilemma. On the one hand, the United States could choose to deploy only the twelve-warhead version of the Trident II missile. In this case, the number of deployed warheads would be equivalent to the number credited to the United States, but the United States would not have the capability against very hard facilities provided by the eight-warhead version. Establishing that capability has been a major objective of this Administration.
On the other hand, the United States could deploy both versions of the missile, retaining the capability of the eight-warhead version. But since each eight-warhead missile would be counted as carrying twelve warheads, the United States would be credited with more warheads than are actually deployed. Under a range of plausible assumptions about the agreement now being negotiated in Geneva, the United States could have roughly 400 to 900 of these "phantom" warheads. Analysis in this study shows that these phantom warheads would diminish the capability of U.S. ballistic missile forces to destroy various notional target sets, though not by more than 10 percentage points following a large Soviet attack. This change might not be great enough to diminish deterrence. Indeed, the major effect of the phantom warheads might be political, since they could cause the United States to have fewer deployed ballistic missile warheads than the Soviet Union under ostensibly equal limits.
Despite these problems, the United States might eventually accept this strategy of crediting the Trident II with twelve warheads just as the Soviet Union might accept the previous strategy.
U.S. acceptance, however, could be contingent on concessions from the Soviet
Union or on changes in U.S. forces that minimize the problems of submarine
survivability and phantom warheads, making negotiation of a treaty more
difficult and time consuming.
ADVANTAGES AND DISADVANTAGES OF LIMITS ON TESTING
Ending development of the twelve-warhead version of the Trident II missile by canceling flight tests of that version might avoid the negotiating complications noted above. Such an approach would develop and deploy only the eight-warhead version.
This approach would avoid complicating negotiations only if the Soviet Union concluded that the United States, by canceling flight tests of the twelve-warhead version, would not have confidence that the twelve-warhead version would work as planned. The Soviet Union might not reach that conclusion. The United States has already conducted one test of the twelve-warhead version; a second test is imminent. Coupled with computer modeling, this might give the United States confidence that the twelve-warhead version would work and would certainly give the Soviet Union some grounds for crediting the Trident II with twelve warheads. On the other hand, the one or two tests represent only the initial step in a full development program. They were conducted with development missiles, not production missiles; they provided no opportunity to test modifications; and they were conducted approximately six to seven years before planned deployment. Thus, if further tests were canceled, there would be reasonable grounds for arguing that the United States had not established the capability to deploy the twelve-warhead version with confidence and that it should be credited with only eight warheads.
This approach imposes only modest disadvantages. The second flight test of the twelve-warhead version, if it has not occurred, would have to be canceled, but that would delay completion of the 30-flight
development program by at most a few months. Nor would this option preclude
deploying smaller warheads--and therefore maintaining the flexibility provided
by deploying two types of warheads~on the Trident II missile. The United
States could decide at a later date to resume development of the twelve-warhead
version; if that decision was made by 1990, it would not affect the current
schedule for deploying that version. Alternatively, a modified version
of the Trident II could be developed that would carry only eight of the
smaller warheads, though this approach could increase costs.
HOW TO IMPOSE TEST LIMITS
If the Congress were to limit flight-testing of the twelve-warhead version of the Trident II, it would need to decide how to limit them. The discussion above assumed that all further testing of the twelve-war head version would be canceled. It would also be possible to continue testing of the twelve-warhead version but only to test that version with eight or fewer warheads.
This approach, however, would offer less assurance of avoiding complications in arms negotiations since the tests, coupled with computer modeling, would probably enable the United States to deploy the twelve-warhead version with confidence that it would work as planned. Consequently, simply restricting tests of the twelve-warhead version to no more than eight warheads at any one time might not strengthen U.S. arguments for crediting the Trident II with only eight warheads.
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