large, bright plume behind it to draw the interceptor. But because fast-burn boosters complete their powered flight at relatively low altitude, the interceptor must fly farther to reach its target. The double whammy is it has to do it in less time. An ICBM which can reach its ballistic coasting velocity in something on the order of a minute may very well be wholly immune to attack by any KKV defense based in space. This morning somebody asked Dr. Cooper and General Kent about the problem of what happens if the Soviets place nuclear weapons in a Soviet kkv-based defense. I disagree a bit with the answers that were given then. I agree that if the number of such missiles were very small, 1, 10, 50, we would ignore it. It would be no different from a small augmentation of the threat we face today. But you see, if that number rises, you can think of them as countermeasures. Countermeasures to the defense. They can strike from any direction with a warning time of, perhaps, 3 or 4 minutes. They may not be, and probably will not be, as accurate as groundbased missiles, ICBMs, and they will certainly not carry as high yield warheads, as ICBMs; but they will be able to reach the ground and they will be able to pass through the defenses. Again, that is a judgment made not only by me, but also by Rockwell International. In a sense, then, the stationing of nuclear missiles in orbit is an ultimate countermeasure. Yes, the Outer Space Treaty prohibits such stationing. It can no way preclude them. It is often argued that this SDI would be worth the cost if it forces the Soviets to replace an entire generation of ICBMs. In fact, however, we know that the Soviets are continuously replacing their ICBM's with new designs. We should expect this process to continue. We should expect it to be accelerated, particularly if the United States moves to deploy defenses which can easily be defeated by the countermeasures which have already been devised. There are many possible responses that the Soviets can make to our strategic defenses. The defending side has the daunting task of thinking of all of the countermeasures which can possibly occur to the offense, and of then taking steps to thwart those countermeasures. The offense, in contrast, need only seek out those few countermeasures which have eluded the defenders in order to mount a successful attack. It doesn't mean we shouldn't pursue a strategic defense program and strategic defense research. What it does mean is we should be very, very careful about where we invest our money, about the political decisions we make. We should be very careful about stepping too far in the direction of point-on-point defenses; that is, where a single missile shoots a single incoming warhead. What we need is a technical surprise. What we need is a volumetric defense, a broom which will sweep thousands of cubic kilometers of space free not merely of missiles, but also of decoys, at once indiscriminately. We don't yet know how to do that. That, I suspect, is the technical surprise that Dr. Happer would hope to see occur, and for that matter, so would I-But I would caution that a technical surprise, unknowable today, is as likely to favor the offense as the defense. Prepared Statement of Peter D. Zimmerman It is a pleasure to be invited to testify before this committee today on the subject of kinetic kill vehicles for strategic defense and the potential Soviet responses to such a deployment by the United States. I hold a Ph.D. in nuclear physics from Stanford University and in addition to performing basic research in physics I have worked extensively in areas of relevance to the analysis of strategic defenses. as I served in the U.S. Arms Control and Disarmament Agency from 1984 to 1986 a William C. Foster Fellow, where I worked in the Strategic Affairs Division of the Strategic Programs Bureau. One of my principal assignments was to follow closely developments in SDI technology. I also had the privilege of serving as an Adviser to our START delegation in Geneva. I do support a vigorous program of pure and applied research in those fields which bear upon the ultimate creation of systems to defend against ballistic missiles. President Reagan has stated the potentially desirable goals of removing the threat of nuclear missiles from the world and of replacing the strategy of mutual deterrence with one of mutual damage denial. These are the only goals I believe worthy of the treasure and dreams of the American people. As I study the plans of the Strategic Defense Initiative Organization I am struck by an impression of an organization in chaos, shifting emphasis each fiscal year. The leading technological candidate has changed from space-based chemical lasers to ground-based free electron lasers and now to space-based interceptor rockets. A decision to deploy defenses against ballistic missiles is a momentous one, to be approached with caution, and a careful examination of the action-reaction cycle of military expenditures. It appears, however, that a system consisting of kinetic kill vehicles (KKVs) in orbit, combined with ground-based late mid-course and terminal interceptors, has emerged as the leading candidate not only for deployment, but for early deployment. I should like to describe some general properties of some parts of such a system and then examine what I think are likely Soviet responses to their deployment. Estimates of the numbers of weapons required and their masses differ. The proponents of early deployment suggest that a highly-effective boost-phase defense can be constructed with only 11,000 interceptors in orbit, deployed on about 2,000 "garages." Barry Blechman and Victor Utgoff calculate that it will require more than 66,000 interceptors deployed on 1,335 battle satellites. This system, Blechman and Utgoff say, might be able to stop 99% of the Soviet missile force in boost phase if each interceptor had a 90% chance of killing its target and if the battle management computer system or the "brain" in each KKV could keep track of the missiles destroyed well enough to allow a second shot at the survivors. For roughly similar assumptions, I size the space-based layer at about 30,000 interceptors. I mention all three values to indicate the extreme range of uncertainty which exists today even among those who have studied the system with care. This uncertainty depends sensitively upon the assumptions the analyst makes about the nature of the Soviet threat and the capabilities of U.S. technologies. Equal or greater uncertainty extends to component costs and to the requirements for space launches. The number of interceptors required increases significantly if the kill probability drops to what is sometimes termed a "modest" 80%. But in assessing these figures we should note that the AIM-9L Sidewinder air-to-air missile, the closest kin to a KKV in today's arsenal, has a kill probability of only 50% in actual combat. The AIM-9L is the twelfth version of this missile, and it incorporates all the refinements developed as a result of experience gained in several conflicts. If the combat performance of a KKV were as poor as that of the best of the air-to-air missiles we have, the number of KKVs required to achieve either the 99% effectiveness of the Blechman-Utgoff study, or the 90% suggested by proponents of early deployment, would skyrocket. The performance estimates and system sizes given above are generally taken to be those of a system in the absence of vigorous Soviet countermeasures, although Blechman and Utgoff have assumed the use of relatively fast-burn Soviet missiles. It is, of course, probable that the Soviet Union would react to U.S. deployment of strategic defenses. I see four generic responses to such a system, some of which will be effective against boost-phase interceptors and others of which will be more potent against mid-course ΟΙ terminal interception. These responses are: Attack the defensive system directly. Increase the number of offensive missiles and warheads. Complicate the task of the defense by using penetration aids extensively. Redesign and replace ballistic missiles either with ballistic which are immune to the system utilization of cruise missiles. - I will discuss each of these generic responses in more detail. Attacking the defenses: Satellites, even the "hardened" satellites postulated for space defense, are relatively vulnerable objects. They travel on predictable trajectories-and the more "armor" they carry, the less able they will be to execute sudden maneuvers to evade an attacker. While a small number of self-defense interceptors might be located on each satellite, that number cannot be large, or the total size and cost of the space-based component of the system will increase. Self-defense rockets might be effective against relatively slow anti-satellite missiles (ASATs) such as the Soviets now use, but it would be less useful against a nuclear armed fastburn interceptor such as the Soviets are developing for their ABM system. Direct ascent ASATS could be launched as precursors to the main force or during the main attack. Relatively low-powered lasers could be used to blind the sensors of battle satellites or of dedicated sensor spacecraft. These lasers would be much less powerful than lasers intended to destroy the structure of a target, and are consequently easier to build and deploy. The U.S. Air Force has already requested funding for development of a ground-based excimer laser ASAT. Even satellites equipped with "meteor bumper" shields can be attacked by dense clouds of debris launched into similar orbits, but moving in the opposite direction. Shields cannot cover an entire spacecraft, and some of the most critical parts such as antennas and sensors must necessarily be exposed. Shielding also increases the requirements for space lift and complicates the design and maintenance of the battle satellites. Increase the number of missiles and warheads The Soviet Union is presently deploying SS-25 mobile missiles and plans to deploy the ten-warhead SS-24 mobile ICBM as well. Although it may be difficult to reallocate resources in a planned economy, we must assume that the assembly lines for these missiles will stay open. Because they are mobile, no large capital costs need be incurred to construct additional silo launchers if the Soviet Union decides it must augment its offensive forces to counter U.S. defenses. Mobile missiles by themselves act as a form of countermeasure to boost phase defenses. That is, mobile missiles can be concentrated for launch in an area comparable in size to that defended by only one or two battle satellites. Since these satellites carry only a few interceptors each, most of the mobile boosters will pass through the boost-phase defenses unattacked. is particularly vulnerable to such measures. A KKV defense It is believed that the SS-18 "heavy" ICBM can carry at least 12 and possibly as many as 14 warheads without modification. For only modest cost the Soviet Strategic Rocket Forces could be expanded by 1232 warheads if the Soviet Union elected to place 14 warheads on each of its 308 SS-18s. Furthermore, a follow-on missile for the SS-18 may already have been tested. Instead of replacing the SS-18 force with its successors, the Soviet Union could opt to construct new silo launchers for its highly fractionated followon missiles while retaining its existing force. This would be a highly "Soviet" response, and might cost far less than the entry price of a U.S. defense system capable of handling the original threat. The United States greatly expanded its missile forces in the late 1960s to counter a perceived Soviet ABM deployment. We should expect the Soviets to respond in much the same way to a U.S. deployment of relatively capable defenses. Unless one unit of defense costs no more than about a tenth of a unit of offense, there is no reason why such a strategy should not be successful for the Soviets. Complicate the life of the defense The most difficult conceptual problem SDI faces is telling the difference, in real time, between Soviet warheads which will have been tracked and - . charted by the defense when they were flight tested - and penetration aids, |