Countermeasures (2000)

April 2000

This is the executive summary from the April 2000 UCS/MIT report "Countermeasures: A Technical Evaluation of the Operational Effectiveness of the Planned US National Missile Defense System"

The National Missile Defense system under development by the United States would be ineffective against even limited ballistic missile attacks from emerging missile states. Moreover, its deployment would increase nuclear dangers from Russia and China, and impede cooperation by these countries in international efforts to control the proliferation of long-range ballistic missiles and weapons of mass destruction.

The United States should reconsider its options for countering the threats posed by long-range ballistic missiles and shelve the current NMD plans as unworkable and counterproductive.

The United States plans to decide in fall 2000 whether to begin deploying a limited national missile defense (NMD) system. This system is intended to defend US territory from limited attacks by tens of intercontinental-range ballistic missiles armed with nuclear, chemical, or biological weapons. Such attacks could include a deliberate attack by an emerging missile state that might acquire such missiles in the future; an accidental, unauthorized, or erroneous attack by Russia; or an attack by China.

The NMD system would use ground-based interceptor missiles to launch "kill vehicles," intended to destroy their targets by colliding with them in the midcourse of their trajectory, outside the earth's atmosphere. The system would track warheads using ground-based radars and satellite-based infrared sensors, and the kill vehicles would use infrared sensors to home on their targets. The planned system would be deployed in phases, with the nominal capability of the system increasing in each phase. If the United States decides this year to begin deployment, the initial phase is to be completed by 2005 and the full system by as early as 2010.

This report examines in detail whether the planned NMD system would work against real world missile attacks. It focuses on the effectiveness of the system against the most commonly cited (and presumably the least sophisticated) threat: attacks by emerging missile states.

While the number of attacking missiles would have a significant impact on the operational effectiveness of the NMD system, of greater importance would be the "countermeasures" an attacker took to confuse, overwhelm, or otherwise defeat the defense. The 1999 National Intelligence Estimate on the ballistic missile threat to the United States -- a document prepared by the US intelligence community -- stated that countermeasures would be available to emerging missile states. Our study first considers the types of countermeasures that a real adversary could use to counter the NMD system, and that the system must therefore expect to face. We then make a detailed technical assessment of the operational effectiveness of the planned NMD system against a limited attack using three specific countermeasures that would be available to any state able to deploy a long-range ballistic missile.

Our analysis of the effectiveness of the NMD system assumes it has all of the sensors and interceptors planned for the full system to be deployed only by 2010 or later. However, countermeasures could be deployed more rapidly and would be available to potential attackers before the United States could deploy even the much less capable first phase of the system.

The contributors to the study are all physicists or engineers. Our analysis is based on an understanding of basic physics and technology and uses only information available in the open literature. This detailed analysis is possible because the United States is now so close to potential deployment that it has selected the specific interceptor and sensor technologies that the NMD system would use. We do not believe that access to classified information would in any significant way alter our study or its conclusions.

The United States must assume that any potential attacker would conduct a similar, although far more sophisticated, analysis.

Overall Findings and Recommendations

(1) Any country capable of deploying a long-range missile would also be able to deploy countermeasures that would defeat the planned NMD system.

Biological or chemical weapons can be divided into many small warheads called "submunitions." Such submunitions, released shortly after boost phase, would overwhelm the planned defense. Moreover, there are no significant technical barriers to their deployment or use. Because submunitions allow for more effective dispersal of biological and chemical agents, an attacker would have a strong incentive to use them even in the absence of missile defenses. The United States should recognize that any long-range missile attack with biological or chemical agents would almost certainly be delivered by submunitions, and that the NMD system could not defend against such an attack.

An attacker using nuclear weapons could also defeat the planned system. An attacker could overwhelm the system by using "anti-simulation balloon decoys," that is, by deploying its nuclear weapons inside balloons and releasing numerous empty balloons along with them. Or an attacker could cover its nuclear warheads with cooled shrouds, which would prevent the kill vehicles from detecting and therefore from homing on the warhead.

Thus, we find that the planned NMD system would not be effective against the limited long-range missile threats it is intended to defend against -- whether from Russia, China, or emerging missile states. We also conclude that deploying the planned NMD system would result in Russian and Chinese reactions that would decrease US security.

Deployment of the planned NMD system would offer the United States very little, if any, protection against limited ballistic missile attacks, while increasing the risks from other more likely and more dangerous threats to US national security.

(2) The upcoming deployment decision will be made on the wrong technical criteria.

The Pentagon will assess the technical readiness of the system prior to the presidential deployment decision. However, this assessment will consider only whether the first phase of the system would be effective against a threat with no credible countermeasures; it will not consider whether the full system would be effective against a threat with realistic countermeasures.

The United States cannot reasonably exclude the issue of countermeasures from a decision to deploy the first phase of the system. A sound understanding of this issue is needed before a deployment decision is made -- even about the first phase. If -- as this study finds -- even the full NMD system would not be effective against an attacker using countermeasures, and an attacker could deploy such countermeasures before even the first phase of the NMD system was operational, it makes no sense to begin deployment.

(3) A deployment decision should be postponed until the system has been tested successfully against realistic countermeasures such as those described in this report.

Tests against realistic countermeasures will not be conducted before the United States makes its planned deployment decision. And it appears that such tests are not even planned to take place before deployment of the initial phase of the system.

The United States should recognize that the planned defense could not counter missiles armed with submunitions filled with biological or chemical weapons, and thus would provide no protection against the threat posed by long-range missiles armed with biological or chemical weapons. For the threat of missiles armed with nuclear warheads, the United States should demonstrate -- first by analysis and then in intercept tests -- that the planned defense would be effective against realistic countermeasures such as those we examine in this study: a nuclear warhead deployed with anti-simulation balloon decoys, and a nuclear warhead covered by a cooled shroud. This should be done before the United States makes a commitment to deploy even the first phase of the planned NMD system.

Detailed Findings

(1) The planned NMD system could be defeated by technically simple countermeasures. Such countermeasures would be available to any emerging missile state that deploys a long-range ballistic missile.

There are numerous tactics that an attacker could use to counter the planned NMD system. None of these countermeasures is new; indeed, most of these ideas are as old as ballistic missiles themselves.

All countries that have deployed long-range ballistic missiles (Britain, China, France, Russia, and the United States) have developed, produced, and in some cases deployed, countermeasures for their missiles. There is no reason to believe that emerging missile states would behave differently, especially when US missile defense development is front-page news.

Many highly effective countermeasures require a lower level of technology than that required to build a long-range ballistic missile (or nuclear weapon). The United States must anticipate that any potentially hostile country developing or acquiring ballistic missiles would have a parallel program to develop or acquire countermeasures to make those missiles effective in the face of US missile defenses. Countermeasure programs could be concealed from US intelligence much more easily than missile programs, and the United States should not assume that a lack of intelligence evidence is evidence that countermeasure programs do not exist.

Many countermeasures are based on basic physical principles and well-understood technologies. As a consequence, a vast amount of technical information relevant to building and deploying countermeasures is publicly available. Any country capable of building a long-range ballistic missile would have the scientific and technical expertise, including people who have worked on missiles for many years, to exploit the available technologies. Moreover, a great deal of technical information about the planned NMD system and its sensors has been published. A potential attacker could learn from a variety of open sources enough about the planned NMD system to design countermeasures to defeat it.

To determine whether technically simple countermeasures would be effective against the planned NMD system, we examined three potential countermeasures in detail: submunitions with biological or chemical weapons, nuclear warheads with anti-simulation balloon decoys, and nuclear warheads with cooled shrouds. We find that any of these would defeat the planned NMD system. They would either significantly degrade the effectiveness of the defense or make it fail completely. Moreover, these countermeasures would defeat the planned NMD system even if they were anticipated by the United States. And because these countermeasures use readily available materials and straightforward technologies, any emerging missile state could readily construct and employ them.

Submunitions with Biological or Chemical Weapons. To deliver biological or chemical weapons by long-range ballistic missile, an attacker could divide the agent for each missile among a hundred or more small warheads, or submunitions, that would be released shortly after boost phase. These submunitions would be too numerous for a limited defense -- such as the planned NMD system -- to even attempt to intercept all of them.

Our analysis demonstrates that the attacker could readily keep the reentry heating of the submunitions low enough to protect the agents from excessive heat. Moreover, because submunitions would distribute the agent over a large area and disseminate it at low speeds, they would be a more effective means of delivering biological and chemical agents by ballistic missile than would a single large warhead. Thus, an attacker would have a strong incentive to use submunitions, aside from any concerns about missile defenses.

Nuclear Weapons with Anti-simulation Balloon Decoys. Anti-simulation is a powerful tactic in which the attacker disguises the warhead to make it look like a decoy, rather than attempting the more difficult task of making every decoy closely resemble a specific warhead.

To use this tactic, the attacker could place a nuclear warhead in a lightweight balloon made of aluminized mylar and release it along with a large number of similar, but empty balloons. The balloon containing the warhead could be made indistinguishable from the empty ones to all the defense sensors -- including the ground-based radars, the satellite-based infrared sensors, and the sensors on the kill vehicle. The defense would therefore need to shoot at all the balloons to prevent the warhead from getting through, but the attacker could deploy so many balloons that the defense would run out of interceptors.

Nuclear Weapons with Cooled Shrouds. The attacker could cover a nuclear warhead with a shroud cooled to a low temperature by liquid nitrogen. The cooled shroud would reduce the infrared radiation emitted by the warhead by a factor of at least one million. This would make it nearly impossible for the kill vehicle's heat-seeking infrared sensors to detect the warhead at a great enough distance to have time to maneuver to hit it.

(2) Many operational and technical factors make the job of the defense more difficult than that of the attacker.

First, the defense must commit to a specific technology and architecture before the attacker does. This permits the attacker to tailor its countermeasures to the specific defense system. Second, the job of the defense is technically much more complex and difficult than that of the offense. This is especially true for defenses using hit-to-kill interceptors, for which there is little margin for error. Third, the defense must work the first time it is used. Fourth, the requirements on defense effectiveness are very high for a system intended to defend against nuclear and biological weapons -- much higher than the requirements on offense effectiveness.

These inherent offensive advantages would enable an attacker to compensate for US technical superiority.

(3) The planned NMD system would not be effective against an accidental or unauthorized attack from Russia, or an erroneous launch based on false warning of a US attack.

Russia has indicated it would respond to a US NMD deployment by deploying countermeasures on its ballistic missiles. As a result, if an accidental, unauthorized, or erroneous Russian attack should occur, the missiles launched would have countermeasures that would defeat the planned NMD system. Moreover, because of the structure of its command system, an unauthorized Russian attack could easily involve 50 or even 500 warheads, which would overwhelm a limited defense. An erroneous attack would likely be large and would also overwhelm a limited defense.

(4) The planned NMD system would not be effective against a Chinese attack.

China has also indicated it would take steps to permit it to penetrate the planned NMD system. China would likely respond by deploying more long-range missiles capable of reaching the United States. More significantly, as the 1999 National Intelligence Estimate notes, China has developed numerous countermeasures. The United States must therefore expect that any Chinese ballistic missile attack -- whether using existing or new missiles -- would be accompanied by effective countermeasures.

(5) Long-range missiles would be neither the only nor the optimum means of delivery for an emerging missile state attacking the United States with nuclear, biological, or chemical weapons.

Other delivery options available to emerging missile states would be less expensive, more reliable, and more accurate than long-range missiles. Moreover, these means could be covertly developed and employed, so that the United States might be unable to identify the attacker and retaliate. These alternative methods of delivery include cruise missiles or short-range ballistic missiles launched from ships off the US coast, nuclear weapons detonated in a US port while still in a shipping container in a cargo ship, and cars or trucks disseminating chemical or biological agents as they are driven through a city.

(6) Available evidence strongly suggests that the Pentagon has greatly underestimated the ability and motivation of emerging missile states to deploy effective countermeasures.

There are strong indications that the Pentagon's Systems Threat Assessment Requirement (STAR) Document and Operational Requirements Document, which describe the type of threat the NMD system must defend against, underestimate the effectiveness of the countermeasures that an emerging missile state could deploy and thus inaccurately describe the actual threat. If the threat assessment and requirements documents do not accurately reflect the real-world threat, then an NMD system designed and built to meet these less demanding requirements will fail in the real world.

(7) The planned testing program for the NMD system is inadequate to assess the operational effectiveness of the system.

A judgement that the planned NMD system can work against realistic countermeasures must be based on sound analysis of the performance of the planned system against feasible countermeasures designed to defeat it. Should such an analysis indicate that the NMD system may be able to deal with such countermeasures, a rigorous testing program that incorporates realistic countermeasures should be created to assess the operational effectiveness of the planned NMD system. The United States should demonstrate that the system could overcome such countermeasures before a deployment decision is made.

Because it may be difficult or impossible to obtain direct information about the countermeasure programs of other states, the United States must rely on other means -- particularly on "red team" programs that develop countermeasures using technology available to emerging missile states -- to assess the countermeasure capabilities of potential attackers. However, existing red team programs are under the financial control and authority of the Ballistic Missile Defense Organization and thus face a fundamental conflict of interest.

To permit a meaningful assessment of the operational effectiveness of the NMD system, the NMD testing program should be restructured. The testing program must

  • ensure that the baseline threat is realistically defined by having the STAR document reviewed by an independent panel of qualified experts
  • conduct tests against the most effective countermeasures that an emerging missile state could reasonably be expected to build
  • use an independent red team to design and build these countermeasures, and employ them in tests without the defense having advance knowledge of the countermeasure characteristics
  • conduct enough tests against countermeasures to determine the effectiveness of the system with high confidence
  • provide for objective assessment of the design and results of the testing program by an independent standing review committee
(8) Past US missile defense tests against missiles using "countermeasures" did not demonstrate that defenses could defeat such countermeasures.

The United States has conducted several missile defense flight tests of exoatmospheric hit-to-kill interceptors that included decoys or other countermeasures and that have been described as demonstrating that the defense could defeat the countermeasures. However, in every case in which the defense was able to distinguish the mock warhead from the decoys, it was only because it knew in advance what the distinguishing characteristics of the different objects would be. These tests reveal nothing about whether the defense could distinguish the warhead in a real attack, in which an attacker could disguise the warhead and deploy decoys that did not have distinguishing characteristics.

(9) NMD deployment would result in large security costs to the United States.

By deploying an ineffective NMD system, the United States would stimulate responses that would produce a net decrease in its national security.

  • Deployment would make it far more difficult to reduce the greatest threat to the security of the United States: an accidental, unauthorized, or erroneous attack from Russia.

    Current US and Russian nuclear weapons deployment and operational policies, which remain largely unchanged since the end of the cold war, carry a risk of accidental, unauthorized, or erroneous attack on the United States. Today, such an attack poses the gravest threat to the United States: it would likely result in the deaths of millions of Americans. Even a deliberate nuclear attack by an emerging missile state would result in far fewer deaths and injuries.

    If the United States deploys its planned NMD system, Russia is likely to increase its reliance on a launch-on-warning strategy, thereby heightening the risk of accidental, unauthorized, or erroneous attack. As Russia has made clear, a US NMD deployment would also limit deep reductions in Russian nuclear weapons, thereby insuring that this threat to US security continues into the future. Deployment would also limit US-Russian cooperation on reducing the dangers posed by Russian nuclear weapons and the risk of theft of Russian nuclear materials.
  • US deployment will affect both the pace and scale of China's missile modernization program, and is likely to lead China to build up both faster and to higher levels than it otherwise would.
  • The adverse implications of NMD deployment by the US would extend beyond the direct responses by Russia and China.

    The deployment of the NMD system could seriously impair efforts to control the proliferation of long-range ballistic missiles and weapons of mass destruction, and thus ultimately increase the threat to the United States from these weapons. Controlling proliferation of these weapons requires the cooperation of Russia and China, which, as the 1999 National Intelligence Estimate stated, will be influenced by their perceptions of US ballistic missile defenses. Moreover, as long as the United States and Russia rely on nuclear deterrence, NMD deployment would place a floor on US-Russian nuclear arms reductions, and thereby put at risk the survival of the broader arms control and non-proliferation regimes. Statements by key US allies reflect their concerns that NMD deployment would decrease international security as well as complicate relations within NATO.
(10) Deterrence will continue to be the ultimate line of defense against attacks on the United States by missiles armed with weapons of mass destruction.

The United States, in concert with other countries, can reduce the missile threat through a combination of export controls and various cooperative measures. If a hostile emerging missile state acquires intercontinental-range missiles, the United States can deter their use through the threat of overwhelming retaliation. If such a state makes an explicit and credible threat to launch a missile attack against the United States, it may be possible to destroy its missiles before they are launched, in accord with the right of self-defense.

The only practical and effective way to address the Russian and Chinese missile threat to the United States is through cooperation, and the deployment of the planned NMD system may limit such cooperation.

Posted April 11, 2000