December 1, 2010  

Maintaining the triad

U.S. bomber force needs a new nuclear cruise missile

Does the U.S. want to maintain a credible bomber leg of the triad of nuclear delivery systems? With little high-level debate, this question may be slowly rolling toward “no” due to the atrophying of the mainstay nuclear weapon of the heavy bomber force, the AGM-86B air-launched cruise missile (ALCM). This is a mistake.

The U.S. and its allies greatly benefit from deploying a capable heavy bomber leg of the triad and therefore should take the appropriate steps to ensure that U.S. bombers can continue effectively to deliver nuclear weapons against defended targets. Specifically, in the fiscal 2011 budget, Congress should fund preliminary steps to begin a replacement program for the ALCM and the administration and Congress should make a long-term commitment to developing and funding the follow-on to the ALCM, the long-range standoff vehicle (LRSO).

Why is this important? Historically, the U.S. has found great value in maintaining a diversified triad of nuclear delivery systems, which protects the ability of U.S. forces to perform their missions even in the face of adverse geopolitical and technical developments. While the submarine force offers survivability and stealth and the ICBM force offers responsiveness and complicates adversary targeting, U.S. nuclear-capable heavy bombers bring their own distinct advantages. For instance, bombers are uniquely effective as stabilizing instruments of political signaling. By generating or forward-deploying elements of the nuclear-armed bomber force, the U.S. can send a strong message to both opponents and allies about its capabilities and intentions, particularly in a time of crisis.

Bombers and their cruise missiles and bombs also present potential adversaries with a different threat than the ballistic missiles of the other two legs of the triad, complicating aspirations for defenses against our strategic forces. Perhaps most importantly, bombers offer a critical technical hedge against failures or vulnerabilities in the submarine force, given the limited upload capacity of our Minuteman III ICBMs. Should something happen to diminish the capabilities of our submarine force, the U.S. can compensate by shifting weight to the bomber leg.

Other advantages of the bomber force include the direct involvement of human control in the delivery system and the ability to recall forces in flight. Recent high-level statements, including the reports of the 2010 Nuclear Posture Review, the 2009 Congressional Strategic Posture Commission and the 2008 Schlesinger Task Force on Defense Nuclear Weapons Management, have validated the continuing need for both the triad and specifically for the bomber force.

Yet the slow decay of the ALCM threatens to cut off the bomber leg. The problem is that the combination of the B-52H and the ALCMs it carries in effect are the nuclear bomber leg. While the stealthy B-2A is equipped to deliver nuclear gravity bombs (though not ALCMs), there are fewer than 20 B-2s and their ability to penetrate airspace defended by next-generation air defense systems and successfully deliver their weapons to target may not be assured. The B-2 alone is simply neither a sufficient nor a credible foundation for a robust nuclear-capable bomber force. The B-1B, meanwhile, is being converted exclusively to conventional use. Until the arrival of a next-generation long-range strike system, this leaves the traditional mainstay of the heavy bomber force, the B-52 (currently the B-52H). Yet the B-52H can only deliver weapons against a defended environment from standoff distances because the bomber, which is approximately a half-century old, cannot reliably evade modern air defenses. It was precisely the recognition of this problem that prompted the Air Force to develop the ALCM in the 1970s (followed by the Advanced Cruise Missile, which has been retired). The ALCMs were designed to launch from their bomber platform well beyond the range of enemy air defenses and travel to their targets while minimizing their exposure to such defenses. Given that the Defense Department plans to maintain approximately 40 nuclear-capable B-52Hs under the New START treaty, each capable of carrying up to 20 ALCMs, maintaining this standoff delivery capability will enable the U.S. to field a substantial number of penetrating weapons in the bomber leg.

Unfortunately, the ALCM, which entered service in 1982, was originally designed for a 10-year service life and is now decaying. The missile has already had its service life extended to 2020, 28 years beyond its original expiration date. Though the Air Force has been studying how to extend it again to 2030, the service’s own assessments have identified components in the missile that cannot be sustained or are becoming obsolete. Meanwhile, though the Air Force requested modest funding for studies on a follow-on to the ALCM in its fiscal 2011 budget request, disarmament advocates have opposed the measure. Nor are an ALCM replacement’s problems confined to doves. The Pentagon has not yet come forward with its plans for future long-range strike capabilities, and the lack of interest in replacing the aging ALCM has been so pervasive within the Air Force and the Defense Department that some analysts have viewed the U.S. as being on a glide path to a dyad rather than a triad. At a national level, the Nuclear Posture Review left the question open as to whether the Air Force’s assessment of alternatives would require replacing the ALCM. Though the situation has improved with the standup of the Air Force’s Global Strike Command, any replacement would have to compete against other service priorities during a period in which defense budgets will be under serious pressure.

However, we should keep the bomber leg and its advantages. The U.S. needs a credible follow-on to the ALCM to provide our potentially vulnerable bomber force with real standoff nuclear-weapons delivery capability. Of course, replacing the ALCM is not a sufficient step for maintaining the bomber leg — it will also require a next-generation penetrating capability for conventional and at least some nuclear missions. But a follow-on to the ALCM is necessary. That means starting a replacement program soon, ideally by approving the Air Force’s request to include preliminary funding for studies for a follow-on to the AGM-86B in the fiscal 2011 budget — and then by actually moving forward on developing and procuring the long-range standoff vehicle in a timely fashion.

Such a program would likely be less risky and less expensive than many comparable defense programs because the focus would be on developing a credible penetrating cruise-missile capability that can be sustained for a long period of time at low cost, rather than focusing on maximizing technological advances and multiplying requirements, which are usually the cause of programmatic overruns and scheduling slips. Further, though the missile would need to be modernized to achieve its mission against air defenses more sophisticated than those the original ALCM faced, much of the program could be built off of existing cruise missile, stealth and other technologies. Indeed, Global Security Newswire reported that a Defense Department source estimated the total program cost might be as low as $1.3 billion. With respect to the warhead, the National Nuclear Security Administration has stated that it plans to extend the life of the W80-1 warhead for the ALCM, which could be used for a follow-on system as well. A replacement ALCM program would also alleviate some of the requirements pressure on the next-generation bomber, which will already be saddled with the formidable challenge of penetrating defended airspace and attacking mobile targets. Furthermore, extending the ALCM would be fully consistent with our arms control obligations, since under New START all heavy bombers are counted as one accountable warhead (under standard loading procedures).

Modernizing the U.S. ALCM capability — and thereby extending the capability of the nuclear-armed heavy bomber fleet — is vital to sustaining a credible triad, which provides depth and resiliency to America’s strategic nuclear deterrent, the foundation of our and our allies’ security. A replacement program will require a long-term commitment on the part of both the administration and Congress in an era of pressure on defense budgets and inflated expectations for disarmament. But funding the initial steps to replace the aging ALCM is an indispensable first step. The administration and Congress should not delay. AFJ

Elbridge Colby is a research analyst at CNA and has served in several national security positions with the U.S. government, most recently with the Defense Department working on the follow-on to the START treaty and as an expert adviser to the Congressional Strategic Posture Commission. Thomas Moore is a senior professional staff member on the Senate Foreign Relations Committee. The views expressed here are their own and do not necessarily represent the views of any institution with which they are affiliated.