During the past 70 years, the United States has invested about $400 billion in ballistic missile defense, mostly on systems intended to intercept long-range, nuclear-armed missiles that might be launched against the United States. But would these systems be reliable and effective against such an attack?
To answer this question, this report considers whether current and proposed systems intended to defend the United States against nuclear-armed North Korean intercontinental ballistic missiles (ICBMs) are—or could be made—effective in preventing a successful ICBM attack by North Korea on the United States. The report focuses on questions that are narrow enough to be answered with some confidence but have broad implications for programs and systems whose goal is to intercept ICBMs in flight. In particular, it focuses on the fundamental question of whether US missile defense systems could defend the continental United States against a baseline threat consisting of a single nuclear-armed ICBM launched from North Korea, or a salvo of 10 ICBMs launched in rapid succession. The report describes the capabilities of current and possible near-term missile defense systems to address the baseline threat and the increased North Korean ICBM threat that can reasonably be expected within the 15-year time horizon of this report.
The report considers a number of missile defense systems that have already been deployed; are currently being considered; or have been proposed to defend against nuclear-armed ICBMs. These systems fall into two main categories: midcourse warhead-intercept systems and boost-phase missile-intercept systems. The proposal to develop a terminal-phase system to intercept ICBM warheads is briefly discussed.
The midcourse warhead intercept systems considered in the report include the Ground-based Midcourse Defense (GMD) system, the sole existing system intended to counter North Korean ICBMs, and the Aegis ballistic missile defense (BMD) system, which was designed to intercept short-, medium-, and intermediate-range ballistic missiles but is now being considered for midcourse-intercept of ICBMs.
After reviewing carefully the technology and test record of the GMD system, the report concludes that its unreliability and vulnerability to countermeasures seriously limits its effectiveness. Because of the difficulty of correcting these deficiencies in a timely or cost-effective way, the report concludes that within the 15-year time horizon it considered, the GMD system cannot be expected to provide a robust or reliable defense against more than the simplest attacks by a small number of relatively unsophisticated missiles. North Korea is likely already capable of launching a more sophisticated attack, according to US national intelligence estimates.
The report also considers boost-phase missile intercept systems, which would attempt to intercept ICBMs during their first few minutes of flight, while their rocket motors are firing. It first describes and evaluates boost-phase intercept systems that would use rocket interceptors based on land, ships, or aircraft, and the drone-based rocket-interceptor system that has been proposed. It finds that all these systems would face very difficult technical challenges. After careful analysis, the report concludes that systems of this type would be unable to defend the entire continental United States. At best, a particular system could theoretically defend part of the U.S. against some of the ICBMs North Korea has.
The report then considers boost-phase missile intercept systems based in space, estimating that over a thousand orbiting weapons would be needed to counter a single North Korean solid-propellant ICBM and that ten times more would be needed to defend against ten launched within a short time. The system would be costly and vulnerable to anti-satellite attacks.
Based on its detailed and careful survey of the literature and analysis of published work, the report finds that creating a reliable and effective defense against the threat posed by even the small number of relatively unsophisticated nuclear-armed ICBMs that it considers remains a daunting challenge. The difficulties are numerous, ranging from the unresolved countermeasures problem for midcourse-intercept to the severe reach-versus-time challenge of boost-phase intercept. Few of the main challenges have been solved, and many of the hard problems are likely to remain formidable over the 15-year time horizon the study considered. The costs and benefits of such an effort therefore need to be weighed carefully.
Supplemental materials about the Report are available. They include the Ballistic Missile Defense Report Corrections and Updates (PDF), the Ballistic Missile Defense Report Technical Supplement (PDF), and the Ballistic Missile Defense Report Biographical Sketches (PDF).