by Robert G. Gard [contact information]
Missile Defense Intercepts in Space: A problem not solved
The Department of Defense asked the Defense Science Board to study the feasibility of an “early intercept” of ballistic missiles, a capability planned for the fourth and final developmental stage of a missile defense program designed to protect Europe from hostile ballistic missiles.
The Defense Science Board is an independent Defense Department advisory body, established in 1956, consisting of outstanding basic and applied scientists to study new weapons systems. A task force of the Board conducted the study, “Science and Technology Issues of Early Intercept Ballistic Missile Defense” from December 2009 to September 2011.
What is remarkable about the study is not its conclusions on early intercept but the extent to which it emphasizes and expresses concern over a different, but related, problem: discriminating between an incoming warhead and “other pieces of the offensive missile complex,” an essential precondition to a successful intercept in space. Thus this report strongly suggests that the currently deployed missile defense systems remain unable to reliably intercept and destroy incoming warheads in space.
U.S. Missile Defense Plans
The concept of the highly expensive U.S. missile defense program is a layered complex of weapons programs tied together in an integrated system of systems. Two of the weapons programs currently under development are designed to intercept incoming warheads in space, above the atmosphere.
One of the two is the Ground-Based Mid-Course System, formerly called National Missile Defense, intended to protect the United States against a limited attack by rogue states when and if they obtain long-range ballistic missiles. The other is the Aegis Ballistic Missile Defense System, currently mounted on cruiser and destroyer warships to counter short- and medium-range ballistic missiles.
To defend U.S. forces and our allies in Europe as part of the NATO missile defense program, a “Phased Adaptive Approach” based on the Aegis system is being developed to intercept ballistic missiles that may be launched from Iran. The plan involves rapid accomplishment of three additional stages of improvements to the currently deployed Block IA Aegis SM (Standard Missile)-3 interceptors.
The next version, Block IB, is intended to include an improved target seeker, an advanced signal processor and improved controls. It is scheduled for deployment in 2015; but it failed its first flight intercept test on 1 September 2011. As a result, procurement of 46 IB missiles planned for Fiscal 2012 has been delayed pending discovery and correction of the problem(s) that caused the test failure, followed by a successful intercept test. The Block IIA interceptor, being developed jointly with Japan, is programmed for deployment in 2018 with a larger kinetic warhead and a burnout velocity 45 to 60 percent faster than the Block IA&B missiles, presumably providing a limited capability to intercept long-range ballistic missiles.
The Feasibility of Early Intercept
The fourth stage, the Block IIB interceptor, also called the Next Generation Aegis program, is scheduled for deployment in 2020 with an improved capability to engage inter-continental ballistic missiles. It is in the competitive design phase contracted with Lockheed Martin, Raytheon and Boeing. The initial expectation was that it would be able to destroy ballistic missiles with ranges of up to 12,000 kilometers in their early stages of flight. If that could be achieved, the Block IIB interceptor indeed would represent a new generation of capability by being able to destroy attacking ballistic missiles before they could effectively release their payloads, thereby preempting the need to solve the problem of discrimination between the warhead(s) and the “other pieces of the offensive missile complex,” including countermeasures.
It was the skepticism of experts concerned about the technical feasibility to achieve intercept of ballistic missiles before effective payload release that prompted the Department of Defense to task the Defense Science Board to conduct the early intercept study. Previous attempts to develop a capability to destroy attacking ballistic missiles in their “Boost Phase,” during the time booster rockets are propelling the payload toward space, had failed or been deemed unworkable.
However, a brief period of time is required following completion of the boost phase to accomplish effective payload deployment. The Defense Science Board report designated “that interval between thrust termination to final deployment of re-entry vehicles and countermeasures” as the “early intercept” (EI) phase. The study noted that successful early intercept could be highly advantageous to the defense of the US homeland against ICBMs launched from a regional adversary.
While some statements in the Defense Science Board report sound tentative and even contradictory at times, the findings are explicit. They include confirmation that boost phase intercept is “currently not feasible,” and statements that early intercept “is not realistically achievable” and “is not a useful objective for missile defense in general or for any particular missile defense system.”
The Discrimination Problem
These findings undoubtedly prompted the task force of the Board to emphasize repeatedly in its report the need for the Missile Defense Agency to deal as a high priority with the problem of discriminating in space between warheads and other objects. The tone of the report’s warnings on this issue strongly implies that its statement that “discrimination in the exo-atmosphere is still not a completely solved problem,” similar to other comments in the body of the report, is a polite understatement.
The report warns that “If the defense should find itself in a situation where it is shooting at missile junk or decoys, the impact … would be dramatic and devastating!” Note the use of the exclamation, rare in such reports. The report also notes that “the ability to dependably discriminate reentry vehicles from penetration aids and other objects“ is an “indispensable characteristic of an effective missile defense system,” and that successful intercepts in space are “predicated on an ability to discriminate the missile warhead(s) from other pieces of the offensive missile complex, such as rocket bodies, miscellaneous hardware, and intentional countermeasures. The importance of achieving reliable midcourse discrimination cannot be overemphasized.” [emphasis mine.]
Recognizing that failure to solve this critical problem means that our missile defense systems that rely on intercepts in space, including the Ground-Based Mid-Course system with interceptors deployed in Alaska and California, as well as the Aegis system, will remain ineffective against adversary capable of deploying missiles with decoys and countermeasures, the Defense Science Board report concludes that “Robust research and testing of discrimination techniques must remain a high priority.”
Several experts have stated that the discrimination problem is not solvable with currently known technologies. It therefore would be prudent, especially in this period of fiscal austerity, to suspend deployment of missile defense systems designed to destroy long-range ballistic missile warheads in space pending demonstration of a solution to the problem of discriminating warheads from other objects.
Lt. General Robert G. Gard, Jr. (USA, ret.) is Chairman of the Center for Arms Control and Non-Proliferation where his work focuses on nuclear nonproliferation, missile defense, Iraq, Afghanistan, military policy, nuclear terrorism, and related national security issues. Gard has written for well-known periodicals that focus on military and international affairs and lectured widely at U.S. and international universities and academic conferences.