Put the Navy in the Lead!

Lieutenant Commander Bart L. Denny, U.S. Navy (Retired)

In 2002, then-Chief of Naval Operations Admiral Vern Clark spelled out his vision for a revised maritime strategy, known as "Sea Power 21." One of the pillars of Sea Power 21, the Sea Shield concept, made clear that Admiral Clark considered ballistic-missile defense a core Navy mission. 1 Then-Vice Admirals Michael Bucchi and Mike Mullen, the authors of Sea Shield, spelled out the need to defend the "sea base" and forward sea ports of debarkation from ballistic missile attack. 2 After succeeding Clark as CNO in 2005, Mullen reiterated the Navy's commitment to ballistic-missile defense in the 2006 Naval Operations Concept.

Today the Aegis BMD Program SM-3 Block I missile-once known as the Navy Theater Wide Defense System-has successfully intercepted ballistic-missile targets outside the earth's atmosphere in 18 of 22 attempts, with testing still under way. 3

In 2003, Congress reversed the Defense Department's cancellation of the Navy Area Defense program, directing the service to reactivate its 100-odd SM-2 Block IVA missiles, and providing $25 million in funds-directly to the Navy, independent of the Missile Defense Agency (MDA-to test and field the missiles as an emergency "Near-Term Sea-based Terminal Defense System." 4 In May 2006, the USS Lake Erie (CG-70) demonstrated the capability of the SM-2 Block IVA in a successful terminal phase engagement. 5

With the introduction of planned, easily introduced upgrades and new systems, sea-based platforms will provide significant advances in detection, tracking, and intercepting ballistic missiles of all ranges in the boost, mid-course, and terminal phases of flight. These capabilities will make the sea-based component of the U.S. Ballistic Missile Defense System (BMDS) a truly national system.

Phase Defenses

Boost Phase. The ability to intercept a ballistic missile while in the powered ascent, or boost phase, of its trajectory remains a capability in development. It is difficult to understate the importance of such a capability, however. An effective boost-phase defense intercepts missiles before they can deploy warheads and countermeasures, presenting interceptors with only one, rather than multiple, targets. Every missile intercepted in the boost phase is one that mid-course-phase and terminal-phase defenses do not have to contend with. Another added benefit of boost-phase defense is that intercept debris is more likely to crash in the launching nation's own territory, possibly serving as an added deterrent against firing the missile. 6

The Kinetic Energy Interceptor (KEI) is a planned land-based boost-phase defense system, which requires emplacement relatively close to enemy launch sites. Recognizing the mobility provided by sea basing the KEI, the MDA advocates a maritime version of the system. But, unlike the Standard Missile family, KEI-at 35 inches in diameter-is far too large to fit in the Navy's Mark 41 Vertical Launch System, or for that matter, within the confines of present-day cruiser and destroyer hulls. Developing the infrastructure to support a sea-based KEI will require a lengthy and expensive acquisition program. 7

As a possible alternative to a costly new warship, the agency could procure a commercial hull on which to mount a number of KEI launchers only slightly modified from their land-based counterparts. This ship need be no more than a barge, towed to her station. The KEI ship would operate in company with a Navy Aegis ship-or future CG(X) cruiser-to provide fire-control data for the missile system and protection against surface, air, and submarine threats.

There may be an even less expensive way to attain a sea-based boost-phase defense. The Independent Working Group on Missile Defense and the Space Relationship 2007 Report noted the SM-3 Block II missile-now under development as a mid-course ICBM interceptor-could be modified to perform boost-phase intercepts by adapting the Advanced Technology Kill Vehicle (ATKV), developed during the late 1980s. The advanced kill vehicle is, according to the report, small and light enough to fit on the Block II missile and capable of attaining the high velocities needed to intercept ballistic missiles in the boost phase. 8

Mid-Course. By 2015, the U.S. Navy, MDA, and Japan's Maritime Self-Defense Force expect to have jointly upgraded the Standard Missile SM-3, enlarging it to 21-inches in diameter along its full length. With the Block II variant, the SM-3 will possess the speed required to intercept ICBMs in mid-course flight. 9 The United States and Japan could further enhance the missile's effectiveness by adding Multiple Kill Vehicle (MKV) technology now under development. Fitted with that, a single SM-3 Block II weapon would be capable of destroying multiple warheads deployed from one ballistic missile.

Terminal Phase. While the service has a terminal-phase interceptor in its SM-2 Block IVA, the Navy considers this missile a "limited, emergency capability." 10 A critical need for advanced sea-based terminal defenses remains to protect ships operating in the littoral, Marines operating near the shore, and seaports where the majority of military equipment arrives from the United States. The Navy considered a sea-based variant of the Army's Patriot PAC-3, but could choose to continue developing its Standard Missile series to fulfill the terminal defense role. The service is already developing the Standard Missile-6 (SM-6) Extended Range Active Missile as an incremental improvement to its air defenses. According to its manufacturer, Raytheon, the SM-6, which builds on the SM-2 Block IVA airframe adding a seeker from the AIM-120 missile, could provide a long-term solution to the Navy's terminal-phase ballistic-missile defense needs.

The Best Choice

Because the wars in Iraq and Afghanistan will likely remain a huge drain on America's military resources, Defense Department leaders will undoubtedly look for ways to economize. Ballistic-missile threats will not diminish, however, and the need to defend the homeland, deployed forces, and allies will continue or become even more urgent. With these considerations in mind, the United States should place a higher priority on its sea-based systems than on land-based or airborne weapons or sensors. In particular, the Department of Defense should further modify and upgrade the Aegis weapon system to a full national missile-defense asset.

Naval assets provide unprecedented mobility, able to reach station anywhere across more than two-thirds of the world in just days-in many places where land-based forces simply cannot reach-ready to fight on arrival, and stay on station indefinitely. Ships do not require airlift, nor do they rely on the goodwill of foreign governments to provide basing rights. Naval assets also provide relatively covert reassurance to otherwise friendly foreign governments who find it politically difficult to allow U.S. forces on their soil.

Aegis BMD ships also provide a long-range surveillance and tracking function, using the AN/SPY-1 radar to provide missile-track data to other Aegis ships and to the land-based elements of BMDS. When not assigned to BMD, the Navy's Aegis ships perform maritime interdiction, cruise-missile strikes, antisubmarine warfare, antiship warfare, and a host of other tasks. While critics argue that ships are more expensive to build, operate, and maintain than land-based missile launchers, such multi-mission capability allows the costs of the ship to be borne across a wide range of warfare areas.

Further, the Aegis BMD system relies on a well-established support base. Indeed, the United States has invested more than $60 billion in the Aegis infrastructure separate of efforts to incorporate BMD capabilities into the system. 11

While it takes several years to build a new Aegis warship, this is nothing compared to the decades required to develop entirely new weapon systems. Aegis BMD ships already operationally deploy with the Fleet. Meanwhile, the Army's Theater High Altitude Area Defense (THAAD) system is still in developmental testing 12 years after its first test flight. This is ironic since THAAD proponents claimed in the 1990s that the system represented a far more mature anti-ballistic-missile capability than Aegis. In fact, Aegis BMD test flights, including technology demonstrations, boast an 82 percent success rate since 1992. The THAAD missile, by comparison, failed in six of eight tests in the late 1990s, prompting DOD to stop flight tests in 2000 for five years of major redesign work before resuming test launches. 12 Similarly, the SM-3 compares favorably with the 78 percent success rate seen in the Ground-Based Interceptor test program. 13 Indeed, Ambassador Henry Cooper, former Strategic Defense Initiative Organization director, has consistently stated that the sea-based BMD program involves the most mature technology of any U.S. system. 14

With its ready availability, solid infrastructure base, mature technology, and inherent mobility, Aegis BMD represents the logical missile defense choice for most countries with a navy. In applications where sea-based assets cannot provide the necessary sensor or weapon coverage, ground-mobile derivatives of naval systems could present a quick and cost-effective solution to ballistic-missile defense requirements. Allies will further benefit from the interoperability of their Aegis BMD systems with their U.S. counterparts.

While sea-based ballistic-missile defenses cannot entirely replace ground-based systems, they offer an inherently mobile, flexible capability, potentially effective against all ballistic missiles in every phase of flight. Given the ability to place sea-based sensors and weapons in areas inaccessible to their landlocked counterparts-a sizeable battlespace, considering the oceans cover more than two-thirds of the globe-the BMDS could not effectively function without its maritime element.

Hat-Trick Capabilities

Were the U.S. government to commit immediately to doing so, maritime ballistic-missile defense assets-building almost entirely on the mature and hardy Aegis infrastructure-could provide the full range of boost, mid-course, and terminal defense against missiles from the SRBM class to large ICBM types by 2015. This capability will come at a fraction of the price of other weapon systems where the Defense Department must build the system infrastructure from scratch.

With all of this flexibility and potential for further growth, the United States should elevate the maritime BMD program to predominance in its National Missile Defense system. In support of this paradigm shift, the U.S. Navy and Missile Defense Agency should:

  • Modify all of the Navy's planned 84 Aegis-equipped ships to include BMD capability. Present plans call for only 18 ships to receive these alterations. At current-day prices, the Navy can accomplish this capability at a cost of $10.5 million and six weeks per ship. 15 By leveraging the economies of scale and by shifting its Aegis computers to an open architecture, the Navy could substantially reduce the per-ship cost.
  • Procure additional SM-3 Block IA missiles. The present acquisition program is for 147 missiles, yet recent DOD studies indicate this inventory is insufficient for near-term potential wartime scenarios. 16
  • Accelerate the SM-3 Block II program. If financial constraints are an issue, sacrifice additional ground-based interceptors to field a sea-based anti-ICBM capability as soon as possible.
  • Add Advanced Technology Kill Vehicle technologies to the SM-3 program immediately, with the aim of fielding sea-based boost phase defense by 2015. If funding constraints will not permit the simultaneous development of KEI and SM-3 boost-defense capability, defer development of the first in favor of ship-based and land-mobile SM-3/ATKV.
  • Add Multiple Kill Vehicle capability to the SM-3 Block IIA. This is important because it could significantly lower the stresses placed on terminal-phase defenses.
  • Examine the feasibility of building land-based systems that take advantage of the Aegis and Standard Missile technologies and support infrastructure as a means of further cost savings. This measure could also improve interoperability between land- and sea-based BMD systems.
  • Encourage foreign operators of Aegis to add BMD capability to their fleets. Japan, Spain, Norway, and South Korea already operate Aegis warships, with Australia soon to follow. The United States should work with allied navies that operate advanced phased-array radar systems, such as the Dutch-German APAR, to develop a BMD capability that is interoperable with Aegis and the Standard Missile series.

The Navy's technologically mature Aegis BMD system has the capacity to incorporate new capabilities. By adopting the suggestions centered on sea-based and maritime derived systems, the United States will be able to field more ballistic-missile defense capabilities in a shorter time, with a potential for significant cost savings, than present programs allow.


1. Admiral Vern Clark, "Sea Power 21: Projecting Decisive Joint Capabilities." U.S. Naval Institute Proceedings, October 2002, p. 32.

2. Vice Admirals Michael Bucchi and Michael Mullen, "Sea Shield: Projecting Global Defensive Assurance." U.S. Naval Institute Proceedings, November 2002, p. 59.

3. MDA, "Aegis Ballistic Missile Defense," Missile Defense Agency Fact Sheet, April 2009.

4. Ronald O'Rourke, Sea-Based Ballistic Missile Defense-Background and Issues for Congress. Washington, DC: Congressional Research Service, 26 June 2007, p. 20.

5. Nick Brown, "U.S. Completes First Terminal Descent Ballistic Missile Intercept." Jane's Navy International, 1 July 2006.

6. Jeffrey Kueter, "The Importance of Boost Phase Missile Defense." The George C. Marshall Institute Policy Outlook, August 2007, p. 2.

7. O'Rourke, Sea-Based Ballistic Missile Defense, p. 20.

8. Robert L. Pfaltzgraff and William R. Van Cleave, co-chairs, Independent Working Group on Missile Defense, the Space Relationship, and the Twenty-First Century 2007 Report. Cambridge, MA: The Institute for Foreign Policy Analysis, 2006, p. 21.

9. Henry F. Cooper and J. D. Williams, "The Earliest Deployment Option-Sea-based Defenses." Inside Missile Defense, 6 September 2006.

10. Brown, "U.S. Completes."

11. Pfaltzgraff and Van Cleave, Independent Working Group on Missile Defense, p. 20.

12. Cooper and Williams. "The Earliest Deployment Option."

13. MDA, "Ground-based Midcourse Defense." In Fact Sheets, August 2007.

14. Henry F. Cooper, "New Life for Sea-Based Defense?" National Review Online, 30 January 2002, and Cooper and Williams, "The Earliest Deployment Option."

15. O'Rourke, Sea-Based Ballistic Missile Defense, p. 7.

16. Ibid. p. 29.

Lieutenant Commander Denny enlisted in the Navy in 1987, and after completing nuclear-power training, served in two submarines. A surface warfare officer from 1998 to 2008, he served in two destroyers before commanding the USS Squall (PC-7) and USS Chinook (PC-9). Immediately preceding his retirement, he served as a missile defense analyst at Headquarters, U.S. Central Command, Tampa, Florida.


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