Defense

researchers made significant progress toward developing naval-based

theater missile defenses during the Clinton administration, the basic

NMD architecture had no naval component because that administration sought actual deployments by 2005–2006.

Once in office, the Bush administration was determined to

accelerate progress on missile defenses, expand research and development efforts, accept a greater degree of technological risk, and

redesign NMD architecture. However, no new missile defense architecture has been proposed. The clear line established in 1997 that

delineated theater missile defenses and national missile defenses

became blurred. The strategy opened the door to a greater seaborne

contribution to defense against ICBMs, and the Navy began to analyze the possibility of this new potential. The Federal Government

developed a broad array of options to exploit the progress that had

been made in Navy theater programs. Then, three events occurred

in December 2001 and January 2002 that further shaped the Navy

program.

On December 13, 2001, the Bush administration announced

that the United States would withdraw from the ABM Treaty in June

2002. Despite the diplomatic drawbacks of this decision, the United

States can now experiment with ship-based missile defenses that the

treaty constrained. When the treaty expires in June, the Pentagon

will test the ability of the Navy’s Aegis radar to track both interceptor and target missiles. The decision to withdraw from the ABM

Treaty also removes constraints from the development of naval systems designed to be effective against shorter-range ballistic missiles.

Overview

Developments of the past 18 months have created new possibilities for the sea basing of national defenses against intercontinental ballistic missiles. Some conceivable designs would

enhance U.S. prospects for defeating a rogue state missile attack

on the United States and its allies, but other deployments could

undermine the Nation’s strategic stability with Russia and

China. The most efficacious architecture from both a technical

and strategic perspective would include a U.S. Navy boost-phase

intercept program and some sea-based radar. Given the complications of using existing Aegis ships for the missile defense mission, the Navy should consider constructing a separate ship

designed solely for this purpose.

Current Technology and Policy Status

The Clinton administration developed its national missile

defense (NMD) strategy in an effort to defend all 50 states as soon as

possible against a limited intercontinental ballistic missile (ICBM)

threat from rogue states. To secure the Nation’s strategic stability visà-vis Russia, the plan emphasized retaining an amended version of

the 1972 Anti-Ballistic Missile (ABM) Treaty. The resulting architecture relied on land-based midcourse interceptors guided by land- and

space-based sensors. The technologies needed for this architecture

had not matured by September 2000, however, and President William

Clinton decided not to deploy the system in 2001. Although the

Toward Missile Defenses from

the Sea

by Hans Binnendijk and George Stewart

Center for Technology and National Security Policy

The National Defense University (NDU) established the Center for Technology and National Security Policy in June 2001 to study the implications of technological

innovation for U.S. national security policy and military planning. The center combines scientific and technical assessments with analyses of current strategic and

defense policy issues. Its major initial areas of focus include: (1) technologies and concepts that encourage and/or enable the transformation of the Armed Forces, 

(2) developments by defense laboratories, (3) investments in research, development, and acquisition and improvements to their processes, (4) relationships among

the Department of Defense, the industrial sector, and academe, and (5) social science techniques that enhance the detection and prevention of conflict. The staff is

led by two senior analysts who hold the Roosevelt Chair of National Security Policy and the Edison Chair of Science and Technology and who can call on the expertise

of the NDU community and colleagues at institutions nationwide. The papers published in the Defense Horizons series present key research and analysis conducted

by the center and its associate members.

A publication of the

Center for Technology and National Security Policy

National Defense University

JUNE 2002

Number 14

Horizons

June 2002 Defense Horizons 1
Hans Binnendijk is Director of the Center for Technology and National Security

Policy at the National Defense University and has served on the National

Security Council Staff as Senior Director for Defense Policy and Arms Control.

Dr. Binnendijk may be contacted via e-mail at binnendijkh@ndu.edu or by

phone at (202) 685–2557. George Stewart is a research analyst at the Center for

Naval Analyses.

As a result, tests of future sea-based systems will begin to move from

the virtual world of high-speed computers to the test range.

The day after announcing its intention to withdraw from the

ABM Treaty, the Bush administration terminated the Navy Area Missile Defense Program, the program for terminal defense against

short-range ballistic missiles, because of cost overruns. Until that

point, some administration officials had envisioned using Navy Area

as an emergency boost-phase interceptor against North Korean missiles. This program had been scheduled to begin testing this year,

with operational deployment to begin by 2004. One likely consequence of the decision to terminate the program will be the delay of

any operational (as opposed to an

experimental or test-bed) seabased missile defense system by

some 2 to 5 years.

Then, the Navy successfully

flight-tested the first fully functional Standard Missile (SM)–3

interceptor on January 25 and

scored a direct hit, using hit-to-kill

technology against a Scud-type test

missile. The SM–3 is the missile associated with the core of the Navy

Mid-course (formerly Navy Theater-Wide) system. The Mid-course

system is the only Navy missile defense program that enjoys any significant funding—seven SM–3 test firings are now scheduled—

although there is neither funding for procurement nor any official

plan for transitioning what is currently an effort at risk reduction

and proof of principle into a procurement program. No one is certain

when project leaders will meld the technologies tested as part of the

Navy Mid-course program into an operational system. An optimistic

guess is about 5 years from now; a pessimistic guess is 10 years.

These three events encouraged additional testing of naval missile defense systems while significantly delaying development of the

foundations of that system. Developers are reengineering the Navy

program, taking much of the steam out of efforts to focus it on ICBM

defenses.

Defending the Nation against ICBMs

One should place the U.S. Navy contribution to missile

defenses in the context of threats from emerging rogue states and

the need to maintain strategic stability with former adversaries.

During the past several years, national intelligence estimates have

indicated a growing missile threat from North Korea, Iran, and Iraq

that will continue to increase throughout this decade. At the same

time, relations with former adversaries have improved, and the

recent Nuclear Posture Review suggests that the United States is no

longer sizing its offensive nuclear forces based primarily on the

need to strike Russian targets. In this context, a reasonable architecture to defend against ICBMs would:

■ be oriented primarily against missiles launched from rogue states

■ try to intercept a missile as early as possible in flight before countermeasures are dispersed and allow time for secondary attempts, if necessary

■ contain a thin layer of ground-based interceptors designed to attack

a missile during its midcourse, should the missile leak through the first line

of defenses.1

These principles call for emphasis on boost-phase missile

defense systems. Unless the boost-phase missile defense system is

space-based, its operating area will necessarily be within about 1,000

kilometers of the ICBM launch

site. This range greatly limits the

effect that a terrestrial boostphase missile defense system

could have on Russia’s or China’s

strategic deterrents. Deploying

boost-phase interceptors in space

is not recommended because such

deployments could intercept Russian and Chinese missiles and

would therefore prove destabilizing. Similarly, deploying groundbased boost-phase interceptors would require stationing them in

Russia to deal with the North Korean threat.

Boost-phase missile defense systems also have the advantage

of attacking an ICBM during the most vulnerable portion of its trajectory. During the boost phase, an ICBM is a large object with a

bright booster plume. Because of the large stresses of launch, even

the slightest amount of damage to the ICBM can result in total

destruction of the entire system. Boost-phase missile defense systems also attack the ICBM before the offense can disperse countermeasures or multiple warheads. Another strong advantage of focusing on boost-phase defenses is the U.S ability to defend its allies

while defending itself.

The technical and operational challenges of the boost-phase

defense require launch of the missile interceptors within 3 to 5 minutes after missile launch. (Some advanced ICBM flight concepts,

such as fast burn and depressed trajectories, can reduce this time

still further, but rogue states’ first-generation ICBMs are unlikely to

have this capability.)

Because the development of most missile defenses to date has

concentrated on midcourse or terminal defense, the technical challenges of building a system capable of detecting, identifying, tracking, and engaging a ballistic missile during its boost phase have not

yet been fully addressed. Even if the system were fully operable, a

barrage attack could result in a few missiles leaking through any

boost-phase defenses. Augmenting the boost-phase missile defense

systems with a thin layer of perhaps 100 midcourse interceptors that

could engage leakers from the boost-phase layer is therefore prudent. Provided that the interceptors can handle the problem of midcourse countermeasures, midcourse defense systems are also advantageous in that they allow a single missile interceptor base to defend

large areas. For example, under the Clinton administration NMD

program, a single site in Alaska could defend the United States

against an ICBM launched from much of the Northern Hemisphere.

2 Defense Horizons June 2002

boost-phase missile defense

systems also have the advantage

of attacking an ICBM during

the most vulnerable portion 

of its trajectory
Such a midcourse insurance policy should not affect Russia’s deterrent posture.

Although the United States need not have many sites from

which missile interceptors are fired for a midcourse defense, the system would require a large network of sensors (for example, radars,

infrared, visible) to detect, identify, and track all ICBM components.

This proposed architecture would be both highly effective

against a rogue state and relatively cost effective. During the next

few decades, rogue states are unlikely to possess more than about 20

ICBMs. Assuming all are launched at the same time, a robust boostphase system should successfully engage considerably more than 60

percent of those missiles. In this stressful scenario, the remaining 8

missiles, containing a total of 8 warheads, and additional decoys

would face 100 U.S. midcourse interceptors. The United States could

afford to launch 4 midcourse interceptors against each real warhead

and up to 17 decoys as a further insurance policy. The cost of this system would be no more than the two phases of the system that the

Clinton administration proposed, which included as many as 250

midcourse interceptors.

Pros and Cons of Sea Basing

Given the events of the past 18 months, the Navy and the new

Missile Defense Agency are now considering systems for a sea-based

ICBM defense that are not unique to ships; at an appropriate site, all

these missiles could be deployed equally well on land. Thus, asking

why the United States should deploy the ICBM defense systems at sea

is reasonable. The primary advantages offered by sea basing include:

■ flexibility offered by making part of the ICBM defense architecture

mobile. The radars and missile interceptors required for defense against

ICBMs are large and heavy. Placing them on board a ship is a cost-effective

way to make them mobile. Mobility offers two advantages: it makes the

defensive missile system less vulnerable to a preemptive strike, and it allows

the United States to change the architecture quickly in response to changes

in the world situation. Officials could withdraw ships if they were no longer

needed or move them if new threats appear.

■ unambiguous control over ICBM defense sites in international

waters. Oceans cover more than two-thirds of the world’s surface. Navy

ships can operate year-round in any ocean—with the notable exception of

the ice-covered Arctic Ocean—without the approval of foreign governments. Thus, sea basing may allow the appropriate placement of ICBM

defense elements outside the United States without a host nation’s permission, which the host nation could revoke under different circumstances if

their and U.S. interests diverge.

Officials must balance the advantages of sea basing, significant

though they may be, with potential disadvantages, including:

■ Operation of a single ICBM defense site continuously requires multiple ships. No matter how efficiently the Navy operates, ICBM defense-capable ships will eventually need to return to port for maintenance and rest for

crews. Consequently, the United States will need to purchase multiple

copies of each ICBM defense system if it desires a continuous presence on

one station. In addition to cost and efficiency, the potential ability to put all

the ships to sea at the same time might create political concerns.

■ Officials must integrate missile defenses deployed on Navy ships

with other combat systems. Current Navy ships are complex platforms capable of performing multiple missions. Technicians must resolve shipboard

integration problems of each new combat system added to the ship, as well

as the technical issues inherent in the system itself. This integration

requires significant resources, particularly when the system is as complex as

the Aegis weapon system, which has figured prominently in many proposals

for hosting missile defense capabilities on Navy ships. Officials can resolve

integration issues, but they must factor these issues into the costs and time

required to put a missile defense system to sea.

■ Missile defenses deployed on Navy ships create the potential for

conflicts between defending against ICBMs and other Navy missions. In

practice, several considerations might rule out simultaneous use of ships for

their traditional missions and defense against ICBMs. Some ICBM defense

areas overlap neatly with expected Navy crisis-operating areas, but others do

not. For example, the Clinton administration’s original architecture relied

on radars in the United Kingdom and Greenland. If a host nation’s concerns

prompted the United States to place these radars on Navy ships instead, the

radars would not be useful for other missions during a crisis in the Middle

East. In addition, executing many of the Navy’s traditional missions requires

putting the ship in harm’s way. If a ship is participating in defending the

United States against ICBMs, limiting that ship’s exposure to risks not associated with ICBM defense might be preferable.

Policymakers must make an important decision regarding hosting missile defense systems at sea: Will existing Navy ships or new

special-purpose ships host the missile defense systems? For example, interceptor missiles could be deployed on special ships akin to

the canceled arsenal ship, and radars could be deployed on special

radar ships, similar to the Cobra Judy radar on the USNS Observation Island.

Hosting the systems on existing combatant ships such as an

Aegis cruiser offers the advantage of enabling the ship to participate

in its own defense. Solid policy reasons also call for keeping major

weapon systems, such as missile interceptors, on military platforms.

However, adding missile defense to the list of existing missions

incurs overhead both in the form of integration of the missile

defense system with other combat systems and a potential opportunity cost of diverting the ship from its original mission designations.

Hosting sea-based systems on special-purpose Navy ships avoids the

integration and potential opportunity costs but does not eliminate

other costs. The United States must still procure additional platforms and provide for their defense. Nevertheless, this solution

might be preferable for some applications.

Contributions to Boost-phase Defense

Although the radar currently in place on Aegis combatants has

enough power and resolution to detect and track ICBMs during the

boost phase, the Navy has optimized system performance and displays to defend against cruise missiles and missiles launched from

airplanes. The required modifications for ICBM defense are not trivial, but they are achievable. What is totally missing at present is a

suitable boost-phase missile interceptor.

Some Navy officials proposed using SM–2 Block IV missiles to

engage boosting ICBMs in the upper atmosphere; that proposal, however, was fraught with a great deal of technical risk and required the

ship to be within 50 kilometers of the launch site, making the ship

itself vulnerable. A more practical approach might be developing a

missile interceptor intended to engage the boosting ICBM later in its

boost phase above the atmosphere, allowing ships to be as far as

1,000 kilometers from the launch site.

June 2002 Defense Horizons 3
Developers could use the SM–3 test missiles being produced for

the Navy’s midcourse risk-reduction effort as a starting point for suitable interceptor missiles.2 Successful boost-phase intercept missiles,

however, would have to be faster than the test missiles. Fortunately,

the launching system on Navy combatants has enough growth potential to support a variety of solutions.

One can only speculate about the length of time required to

develop a suitable missile and to integrate it with the Aegis weapons

system. Prior to the cancellation of the Navy Area program, optimistic estimates by some Navy officials were as low as 6 years to produce boost-phase missile interceptors for ship tests. Because all

work on shipboard integration of missile defense systems is currently

suspended, this timeline has probably increased.

Using the modified SM–3 or wide-diameter missiles (fast-accelerating interceptors with high terminal speeds), the ship could be as

far as 1,000 kilometers from the launch point. Navy ships thus

equipped in international waters could engage missiles launched

from all of North Korea or Iraq. The effectiveness of sea-based boostphase missile interceptors against ICBMs launched from Iran would

depend on the part of the country from which the ICBMs were

launched. In some cases, U.S. forces

would need ground-based or airborne

supplements.

A sea-based boost-phase capability

has clear political advantages and some

disadvantages. Its main advantage is

the ability to provide a potential

defense against ICBMs launched from

North Korea and most parts of the Middle East. At the same time, sea basing

would present no threat to Russia’s and

China’s land-based ICBM deterrents because those launch points are

far inland.

As for disadvantages, a sea-based boost-phase system would

potentially threaten Russia’s submarine-launched deterrent, assuming a capability existed to estimate the general location of the submarine. Second, any boost-phase defenses would require the establishment of a “no-launch zone” or other special procedures over the

rogue state and a willingness in extremis to delegate the engagement

decision to the local U.S. commander. Both requirements might be

difficult to sustain politically. Finally, any boost-phase concept would

require launching the interceptors in the direction of the country

launching the ICBMs as well as toward third parties that might not

be involved. For example, launches against North Korean missiles

with boost-phase missile interceptors would entail launches on

azimuths toward both North Korea and China. When defending

against Iraqi and Iranian missile launches, the boost-phase missile

interceptors would fly over several countries on an azimuth toward

Russia. Additionally, debris from the engagement (for example, damaged warheads or spent interceptor boosters) could have an impact

on uninvolved countries.

If the United States accepts the political disadvantages, the

operational advantages of a sea-based boost-phase interceptor are

significant. With the potential exception of Iran, these interceptors

are most effective against the countries in need of dissuasion and

deterrence, and they are less effective against former adversaries

that need reassurance. If the United States requires continuous 

protection, the mission would require the deployment of several missile-defense ships, but that investment is relatively small compared

with the potential cost of a missile strike against the United States.

Considering the short time frame involved in such an attack, however, developing an additional layer that would help achieve the goal

of designing a robust defense against ICBMs launched by rogue

states seems prudent.

Midcourse Defense

Any midcourse ICBM defense system depends critically on 

sensor support. Therefore, the possibility of basing high-power, fineresolution radars at sea to provide sensor support must precede a

discussion of the possibility of sea-basing midcourse missile interceptors. These two issues are treated separately, but putting both on

the same ship would be quite possible.

Sea-based Radars. Although the ABM Treaty has prohibited formal testing, the current S-band radar (SPY–1) used by the Aegis

weapon system can track large objects, such as boosters, at distances

well above the atmosphere. Testing is

required to determine the extent of the

current SPY–1 radar’s contribution to a

midcourse defense system, but any

solution to the countermeasure problem will likely require the development

of radars with even higher power and

finer resolution.

Navy officials have stated that

using the existing SPY–1 radar coupled

with software modifications to track

objects in space is one near-term possibility. Depending on the target, the maximum detection and tracking range of the radar would

be 500 to 1,000 kilometers. This capability would support midcourse

engagements of early-generation ICBM systems developed by rogue

states with few or no countermeasures. The same Navy officials estimate that it will take about 9 years to increase the power and resolution of the systems to detect objects, to provide discrimination

clues, and to track all the individual elements of a cluster as far away

as 3,000 kilometers. The effort will also involve developing X-band

and S-band radars, both of which are new technology.

Using the current X-band technology developed for the NMD

program, adapting it for use at sea, and placing it on board a ship is

another possibility. The maximum detection and tracking range of

these radars is 2,000 to 4,000 kilometers. Whereas the Navy could

retrofit these radars onto existing Navy combatants, their weight,

power, and cooling needs would require removal of many combat systems currently in place. As a result, some proponents of this idea suggest that the sensor ship should be a noncombatant and should use a

commercial hull. The minimum time required for the integration,

design, and conversion of an existing hull is about 5 years.

Sea-based radars contribute uniquely to midcourse intercepts.

The curvature of the Earth limits the detection and tracking ranges

of any radar. Officials will find presumably appropriate land-based

sites for radars to track incoming missiles as they approach the

4 Defense Horizons June 2002

if the United States accepts

the political disadvantages,

the operational advantages

of a sea-based boost-phase

interceptor are significant
United States. Sea basing can place a radar that is completely under

U.S. control much closer to the launch site than is possible from sovereign U.S. territory. Indeed, if support from a host nation is not

forthcoming, sea basing might be the only option for placing highpower radars closer to the launch site. Two factors make this radar

placement desirable:

■ Sea basing would help develop sufficient information to engage the

ICBM in early midcourse, an important consideration in a battle that will be

over, for better or for worse, in 15 to 30 minutes.

■ Observing deployment of the payload would provide additional

information that might help identify the warhead(s) amid the cluster of

debris and deliberate countermeasures.

Naval deployment of radars to detect ICBMs might be useful for

two other reasons. First, both Great Britain and Denmark have been

reluctant to accept the Clinton administration’s suggestion to deploy

X-band radars at Fylingdales and Thule, respectively. Even though

ground-based radars are more reliable, naval deployments provide

an alternative. Second, if the Space-Based Infrared Systems

(SBIRS)-High and -Low now in development continue to face technological and funding problems, demand for naval radar deployments could increase.

Sea-based radars should not undermine strategic stability.

They would not enable similar early detection and tracking of ICBMs

launched from the interior of Russia and China, reducing the political risks. Verification for future arms control regimes, however, is

one potential political complication. If the United States links existing Aegis radars (or any other radar the Navy uses widely) into an

ICBM missile-defense network, then all ships with that radar

become potential strategic assets and a likely topic of future arms

control negotiations with Russia. Russia would probably seek on-site

inspections, restrictions on the operating areas of ships, and limits

on the number of capable ships, inhibiting the Navy’s freedom to use

these ships in other missions.

Using radars on board existing naval combatants for a midcourse defense system against ICBMs appears feasible and might

have definite advantages. The disadvantage again would be the

opportunity cost of diverting those ships from the missions for which

the Navy originally constructed them. This disadvantage is offset

somewhat when the ships are employed in forward locations where

they might simultaneously participate in other missions that do not

put their strategic mission at risk.

Sea-based Missile Interceptors. Defense missiles currently procured for testing have a maximum speed of about 3.1 kilometers per

second. This speed would adequately defend against intermediaterange ballistic missiles, but designers must increase the speed of the

interceptor missile for a robust capability against ICBMs. Engineers

estimate that they could modify the current launch systems used on

Navy combatants to accept missiles with larger diameters and capable of speeds of 6.5 kilometers per second or more. That type of interceptor missile could defend an area the size of a continent or larger

and could handle ICBMs with advanced capabilities. Generally,

developing these newer, faster missile interceptors with improved

kill vehicles will take 6 to 15 years.

A priority for the Navy and regional CINCs is developing missile

defense systems effective against longer-range theater missiles

under development in some rogue states. Given appropriate sensor

support, such missiles would also possess at least a rudimentary

capability against ICBMs. In fact, at times, these missiles could perform both missions simultaneously. For example, with proper sensor

support, a ship with fast midcourse missile interceptors in the North

Sea could defend large parts of Europe and the U.S. eastern

seaboard against missiles launched from the Middle East. This feature is beneficial because it enhances the utility of these weapons

systems but also damaging because it blurs the boundary between

strategic and nonstrategic uses regarding strategic stability.

Notwithstanding the large areas that a single missile interceptor facility can defend, launching midcourse-system missile interceptors from multiple sites has several advantages:

■ Suppression of the sea-based midcourse missile interceptor system

is more difficult.

■ Interceptors offer greater flexibility regarding the location of target

engagement, an important consideration when dealing with nuclear warheads designed to detonate when successfully engaged.3

Midcourse interceptors allow for a shoot-look-shoot firing doctrine: the defense fires one interceptor missile, evaluates the results,

and fires a second (or more) interceptor missile only if the first

interceptor misses. The shoot-look-shoot concept preserves missile

inventory and greatly simplifies battle management by minimizing

the number of interceptor missiles in flight at any given time, again

an important consideration when one envisions defending against

small raids of more than one ICBM.

The ability to build a land-based capability on U.S. territory to

permit more than one engagement in the latter part of the midcourse suggests that decisionmakers should choose operating areas

for ships with midcourse ICBM interceptors based either on the

ability to engage the ICBM early in the midcourse or the extension

of the defensive area to cover allies or U.S. forces deployed forward

in portions of the world far from the United States. Nevertheless,

even with these general guidelines, determining definitive operating areas for Navy ships in support of midcourse missile defense

against ICBMs is difficult.

Maintaining Strategic Stability

Without the ABM Treaty, which will effectively end in June, the

United States must maintain strategic stability with Russia and

China in other ways requiring even more vigilance, now without the

treaty’s negotiated guidelines. For the Bush administration to conclude a long-term strategic framework with Russia successfully, the

United States may need to accept some constraints on missile

defenses. Would those constraints allow for the eventual deployment

of a limited number of naval ships with radars and interceptors capable of defeating an ICBM?

The United States could negotiate such a new framework without abandoning sea-based missile defenses. If the sea-based interceptors are limited to the boost phase, they would not have adequate

range to intercept ICBMs launched from Russia. Line-of-sight radars

based on ships deployed near North Korea and the Persian Gulf

would also have limited capabilities against Russian ICBMs. Russia

might seek to limit the number of ships deployed with ICBM defense

capabilities, their stationing area, or the range of sea-based radars.

June 2002 Defense Horizons 5
capability would have missile defense as their principal mission and

that all other missions would be secondary. Finally, the President

would have to delegate the authority to shoot down a missile in boost

phase to the commander of the ship or to some other commander

who could act in seconds. That situation might cause potential diplomatic problems, but in practice other missile defense concepts

would probably also entail delegation of similar authority to personnel at the operational level.

An alternative, which might benefit arms control and operations, would be the construction of separate ships designed solely

for intercept and radar missions. The missile defense ships would

then be separate from the Aegis fleet, and the other side could verify any limitations more easily. The cost constraints associated with

new construction, however, might slow the existing Navy shipbuilding program.

Sea basing of midcourse missile interceptors or terminal

defense systems against ICBMs is a much less attractive alternative.

Better land-based alternatives for midcourse intercepts, which

would be less destabilizing and would not mix theater and national

missile defenses, are available. Defense of a large enough area to be

anything other than the last-ditch defense of important strategic

facilities is simply impossible for terminal defense systems of the

continental United States. Those defense facilities, however, generally do not move; therefore, paying a premium for making the

defense system mobile does not seem sensible.

In summary, deployment of a small number of sea-based radars

and boost-phase interceptors is sensible for dealing with a limited

threat from a rogue state. The United States must manage the difficulties, not the least of which is persuading Russia and China that

such deployments do not undermine strategic stability. If U.S. military officials properly design the architecture, however, overcoming

that problem should not be an impossible task.

Notes

This essay originally appeared in The Washington Quarterly 25, no. 3 (Summer

2002), pp. 193–206. It is reprinted by permission. 1 See Hans Binnendijk, “How to Build an International Consensus for Missile

Defense,” International Herald Tribune, March 7, 2001. 2 The SM–3 was designed to intercept a shorter-range missile during the midcourse of its flight and is therefore often called a midcourse interceptor, but it could

be used against an ICBM during the exo-atmospheric part of its boost phase. 3 Commonly called salvage-fusing, the premature nuclear detonation temporarily blinds sensors attempting to detect targets in the vicinity of the explosion and creates a potentially damaging pulse of electromagnetic energy that can damage nearby

systems in space and on the ground below.

Moscow also might seek assurances that the United States will not

use sea-based systems against Russia’s submarine-launched missiles.

The most difficult strategic stability problem to resolve is the

possibility that Russia might assume that all Aegis radars and interceptors have at least some NMD capabilities if some naval systems

with theater missile defense capabilities are networked into the

NMD system. Thus, during negotiations for a new strategic framework, the task will be to convince the Russians that this capability is

limited and does not undermine Russian deterrence. One possibility

would be, first, to create a boost-phase interceptor that requires a

modified launch system visible from outside the ship for inspection

and verification purposes and then, second, to limit the number of

those systems deployed on Aegis ships.

The problem vis-à-vis China is more difficult because the Chinese have only a few dozen land-based single-warhead missiles capable of striking the United States. Sea-based boost-phase interceptors

should not present a threat to Chinese ICBMs launched from the

country’s interior. On the other hand, China could view sea-based Xband radars linked to even a limited number of midcourse interceptors as affecting their current deterrence. The Chinese are modernizing their ICBM force anyway, though, and the number of warheads

capable of striking the United States could multiply several times

during the coming decade, even without U.S. missile defenses. Ideally, China will not pursue options to place multiple warheads on its

missiles. The missile defense architecture suggested above provides

the best prospect to dissuade the Chinese from this path while still

providing credible protection against rogue states.

The Sea-based Advantage

Using missile interceptors based at sea to defend the United

States against ICBMs offers several advantages, the most important

of which are flexibility and control. The system involves costs as well,

however, including operational limitations for other missions and

competition for resources to build new ships.

The most cost-effective option for a potential seaborne deployment is the use of upgraded Aegis radars and modified SM–3 missiles

for boost-phase intercepts on board existing combat ships stationed

near the Korean Peninsula and the eastern Mediterranean. In addition to providing a layer of boost-phase defense, ships at these locations would provide radar coverage early in the flight of an ICBM—

a valuable asset to the midcourse defense layer. These locations

overlap with current Navy forward-operating areas, which would

help mitigate the opportunity cost to existing missions that the new

mission entails.

Estimating the availability of this capability is difficult. Assuming

the United States decides to pursue this approach in the near future,

the end of the decade is a reasonable deadline expectation. Landbased systems for the midcourse defense layer could mature earlier.

Then, deployed ships could initially provide radar support, and the

boost-phase capability could be added as it becomes available.

This option involves several costs that officials must manage.

The United States must maintain strategic stability with the Russians and Chinese and convince them that such deployments would

not undermine their deterrents—a difficult but not impossible task.

The Navy would need to accept that Aegis ships deployed with this

6 Defense Horizons June 2002

Defense Horizons is published by the Center for Technology and National Security Policy through the

Publication Directorate of the Institute for National Strategic Studies, National Defense University.

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The opinions, conclusions, and recommendations expressed or implied within are those of the

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department or agency of the Federal Government.

Center for Technology and National Security Policy

Hans Binnendijk

Director