DEFENSE OF HARD POINTS
Defense of the United States retaliatory force (including command and control centers) against ICBM attack can be accomplished to some degree by: increasing numbers, hardening, concealment, and active defense.
A plausible case can be made to show that hardening plus active defense offers economic and reliability advantages over the other alternatives for some important elements of the United States retaliatory arsenal. This claim must be tempered, however, by an appreciation of technological uncertainties which prevent a positive statement at this date that active defense of hard points is technically feasible at a level of deployment which makes it economically attractive.
Hard point defense is, beyond much question, easier and less expensive to accomplish than defense of soft areas. Since the target is hard, the incoming missile may be allowed to come within about ten thousand feet of its target prior to interception. In consequence, commitment of the AICBM weapon may be delayed until the ICBM is within ten-to-twenty miles of the target, rather than the sixty-to-one hundred miles minimum commitment range for ZEUS, for example. This results in less expensive interceptors and very likely reduces the cost of other system elements as well. The decoy problem is also eased, as decoys to be effective must be capable of surviving the most rigorous re-entry problems without disclosing their characteristics to observing radars, and must have been precisely deployed in order to appear to impact within ten thousand feet of the target.
The Air Force has recently concluded eight studies (six unfunded, two funded, for a total of $140,000) of the means of defending a hardened restricted area against ballistic missile attack. The RAND Corporation and Bell Telephone Laboratories have also recently concluded similar studies. These studies indicate that reasonably good defense of small sites hardened to about 100 psi can be bought at a five-year cost in the range of ten-to-fifty million dollars, depending upon the severity of the postulated threat.
While it seems quite likely that a hard point defense system costing fifty million per defended site or somewhat less could be built with the capability of handling perhaps ten decoys per missile attack, the costs would rise almost linearly with increasing numbers of re-entry decoys. As of now it is not known whether it is possible to perfect decoys which weigh a few tens of pounds or less, and which can survive re-entry while matching medium or large warheads in CEP and characteristics observable by radar.
Until this crucial uncertainty is resolved, the feasibility of hard point defense at reasonable cost cannot be determined.
A technically different approach to hard point defense (for example, HELMET) is being given some consideration. Rather than employing anti-missiles which seek out incoming missiles and are therefore vulnerable to decoying, these concepts involve lofting a barrage of pellets through which dangerous objects would have to fly. Warhead and decoy alike would be destroyed if the barrier were sufficiently high (so that atmospheric slowdown had not occurred) and the pellets of the barrage sufficiently heavy to accomplish kill. Considering the uncertainty of our current knowledge, the weight of pellets required may range from one million to one hundred million pounds per attack for each hard target defended. Systems of this kind have not yet been examined closely enough to determine their cost or susceptibility to specific countermeasures.
Another significant uncertainty relates to the feasibility of countering the effects on defense systems of large, low-altitude, nuclear bursts; or alternatively, the possibility of successfully attacking with weapons which deny the possibility of the enemy's warheads detonating.
The Penetration Aids program as well as the decoy discrimination research carried on in ZEUS and DEFENDER will go a long way toward resolving the uncertainties in decoy capability. Resolving the questions raised by possible nuclear detonations is not possible without testing; but theoretical studies based on available data may furnish a useful degree of knowledge.
The Air Force has estimated that about [REDACTED] would be required between the start of weapon system development and IOC. Some research in hard point defense technology is being conducted at present, and some of the system problems are closely related to those experienced in ZEUS and ARPAT. Increasing the effort on technology related to hard point defense (especially work on high thrust, short-burning time interceptors) is desirable at this time. Some limited systems work should be undertaken to pin down costs and prepare for possible weapon system development.
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