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Basing Alternatives and Technical Background EUGENE SEVIN Defense Nuclear Agency Washington, D.C. Gentlemen, I want to express appreciation on the part of the Defense Nuclear Agency (DNA) for the fact that so distinguished and prestigious a group as this is devoting its thoughts and talents to the problems that are facing the Department of Defense at the moment. I would like to make a couple of points in the few minutes allotted me. The first is that the deep basing option has been around for a num- ber of years; a number of considerations and a number of investigations have been directed to this possibility, not only for missile basing but for other military purposes. It was not a system invented in the last minutes of the Presidential decision. If there is a window of vulnerability at the moment, I would like to believe there is, also, a window of opportunity, so that by l984, if the decision does not favor the schemes we are thinking about now, at least we have left some legacy to the engineering profession and we know a bit more about things than we do at the moment, and there will be at least a better basis on which to make intelligent engineering decisions in the future. So, I think we have an opportunity. Over the past 20 years we have gotten to a point where we believe that there are certain essential at- tributes of deep underground basing. So here is a mini-course in the evolution—my view of the evolution—of deep basing (Figure l). Things started about the early to middle l960s, with a view toward concentrating resources deeply underground and requiring proliferation of surface por- tals to get out. There were two essential problems. First, this was a high-value target, and encouraged an enemy to direct a substantial at- tack toward it, and as the threat went up, the depth of burial went down, and pretty soon it went down to a point where economically, at least at that point in time, it did not seem feasible. So, the concentration of assets underground was deemed not a good idea. The second objection was that the means of egress depended on there being some portal or portals remaining undamaged; that is, after attack they had to have the same capability as they had before attack, and with the increase in accuracy that was mentioned by Colonel Berry, and the limited number of portals 20

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2l which could be afforded, each one could be targeted, and there was no way to get out. During the so-called "Strat X study" in the later l960s, the thought was to distribute the underground assets within an interconnected tunnel system. The depth of burial was to be reduced by finding a hard rock site, but a large number of exit portals were required since, as before, some had to survive the attack. The utility of this scheme was found to lie more in the distribution of assets than in the distribution of attack points, but with increasing accuracy of the attacker, the requirement to ensure the postattack integrity of an egress portal had to be given up. Somewhat later, in the early l970s, several schemes were developed to restore a vertical egress shaft after attack. On a scale of bizarre- ness of from l to l0, in my view these schemes came out somewhere be- tween 5 and 9.9. While possible, I think it is definitely a challenge to make systems of such a nature work, particularly in view of the unknown characteris- tics of the portal region after an attack. But clever schemes have been proposed, and you will hear about some of them, I believe, today. To recapitulate, our view is that we need to distribute assets at some substantial depth below the ground. We need to give up the notion that at least some egress portals must survive the attack. So, we have to be completely self-sufficient from the inside out, and if we cannot do that, then we probably do not have a credible scheme. There is an ob- vious consequence; namely, that the system response time will not be as immediate as some would like, and therefore that the attributes of a deep underground system, which are more or less constrained, have got to be entirely consistent with the mission and roles that are expected of a missile force based in this manner. Okay, so I guess my first point is that we have come a way. We have a reasonable idea, not a single concept, not a baseline concept today, but the general characteristics and general attributes of a deep under- ground system are fairly well understood. I think we have to be careful to do something useful in the relatively short time we have been given by this Administration, and not to go too far afield from things that have been properly discarded in the past. On the other hand, we should not be dogmatic about rejecting past ideas. My second point has to do with uncertainties. In developing and deciding to deploy a deep basing system, we are going to have to learn to live with uncertainties to a degree beyond which perhaps we, as en- gineers, have been willing to admit heretofore. Figure 2 illustrates something of what is known about the shock environments at depth intro- duced by nuclear weapons detonated at the surface. I have suggested a porous rock, perhaps a tuff that we might find at the Nevada test site, and I show depth contours at which one could expect 0.5 kilobar of stress from a large megaton-size weapon (in fact a l00-megaton weapon, which is a larger weapon than presently is in anybody's arsenal). So, to talk in terms of facilities intended to survive these kinds of yields already is to stress an attacker, and probably cause him to aggregate smaller wea- pons and set them off simultaneously.

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22 I have suggested an uncertainty in the data base that, expressed in range, is roughly a factor of two, and is a consequence of several things, I believe. First of all, there is the essential uncertainty, or random- ness of behavior, associated with shock propagation in geologic media. Secondly, we suffer from the fact that the data base that we have, while it is fairly substantial with regard to tamped bursts (i.e., nuclear bursts that are fully contained), has no relevant data on modern, high- yield weapons detonated at the surface of the ground. Therefore, the basis that we have for inferring relationships between yield, stress, and depth of burial such as those shown in the figure is indeed inferen- tial. That has been done in the past by simulating a free surface burst underground—setting off a small weapon in a small cavity—and so the data also is subject to uncertainties of a systematic or bias nature. We may be wrong in the key that we have chosen to use in unlocking the tamp data and relating it to surface burst conditions. Although we think we have related the tamp data to surface burst conditions in a design conservative way, we may be wrong. We plan to conduct an underground test involving a cavity of 40 meters or larger that would allow us to study the nature of the energy coupling of the bomb to the surface, the early stages of crater formation, and shock propagation into the ground. This would be a very major undertaking, but we plan to do it. I have talked so far about free field stresses or free field condi- tions. Let me turn now to response of the buried facilities. A third element of uncertainty has to do with survivability of underground open- ings. In a hard rock—perhaps a granitic rock, which is less dissipa- tive and more elastic in its wave transmission characteristics—one would find that these kinds of environments would occur at greater depths than in soft rock. At the same time, one could expect a cavity or a tunnel to survive at higher stress levels. So there is a trade between the depth at which one would like to put the facility and the costs associat- ed with hardening or making the cavity survivable. The point, of course, is that the selection of a site from the point of view of survivability is something that has to interact very strongly with site selection from the point of view of constructibility, maintenance, and public accept- ability. From a survivability point of view, there is such a thing as a bene- ficial site; that is a porous over hard layered site, perhaps with cap rock at the surface to discourage penetrating-type weapons. One would utilize the porous overburden for its dissipative (shock attenuating) properties, and then utilize the stronger, more competent material be- low in which facilities could survive at greater stress levels (or re- quire a lesser amount of hardening). Finally, this chart also carries an implication from an attacker's point of view, since uncertainties in burial depth of a factor of two are really quite bothersome. Pressure-range relations scale as the cube root of weapon yield. Thus, for an attacker to be sure that he has im- posed, say, 0.5 kilobar stress on a facility at known depth of burial, he would have to increase the yields shown here by a factor of eight. Where we may have designed a facility to survive a l00-megaton attack,

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23 he may look upon it as a target requiring at least 800 megatons to en- sure acceptable (to him) levels of damage. Also, the attacker is going to have a difficult time understanding what, in fact, he did accomplish. However, let me emphasize that this view of uncertainty, which may be favorable from our perception of the attacker's problem, is not all that helpful when we are planning an enormously expensive engineering under- taking and are expected to quantify, to the extent possible, the notion of risk. In summary, let me say that we think the required technology exists (Figure 3) in the sense that the work of the past years, much of which you will hear about today, provides an existence proof, a proof of en- gineering principle. There is a substantial amount of engineering data that is not in hand, and, before the Air Force and the Department of De- fense could go forward with an acquisition program, risks would have to be reduced to a point compatible with the way the Department of Defense goes about its business and makes its decisions. We are entering into a concept validation program in which we have to expand our considera- tion of admissible deep basing concepts, so that we have a fair set from among which to make a best choice. We have to document very well not only why we have made the choice from among that set, but also that other concepts were excluded for good and sufficient reasons. So, we have to document not only what we recommend to do but also what we have chosen not to do, and we have to carry out those sorts of technology and engi- neering demonstration activities that, indeed, will provide sufficient data for an informative and intelligent engineering decision. Over the past years, and most notably since l976, we have tried to address deep underground basing technology in a very systematic and rela- tively exhaustive fashion, trying to identify which aspects of design, construction and operation were in hand from an engineering point of view, and which, in fact, were technology issues around which we either could not pass or for which proposed solutions simply lacked credibility. In those latter areas is where we have concentrated our resources and ef- forts. I trust that we will convey to you during the course of this meeting where we think we are, and the basis for our proposed efforts. There is a great deal that needs to be done and we are appreciative of the fact that the U.S. National Committee has chosen to address it- self to this problem which, to the Department of Defense, the Air Force, DNA, at the moment is of really very significant importance.

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26 s~~-~ — O u a E ui y LI t— w ^ a _ 0xperience Mines; civil/com tunneling DO0/0PRI/CON UTC demo in NY Underground nuclear tests Underground nuclear tests Minuteman; ship submarines Mine rescue; UG' data telem (Disci ThrowerS Husky 1 Mighty 0pic); Sanguine c r» c c 'x Requireme Muck handlini & disposal Megawatt size fuel cells Definition of attack environ Survivable rock openings Shock isolatio rhrough-earth communicatio UJ O) 0 o c o 0) •S L S o= Required T 0xperience Mines; subways; aqueducts; hwy.Er r tunnels; hydro powe plants; NTS UGT complexes; Chicagc storm water sys; NORAD CMCC;site Mines; submarines; hydro power plants underground offices ft factories & ware houses; NORAD; Site R' Submarines, space vehicles Mines; submarines; space vehicles NORAD CMCC; site R; safeguard •o _t 5 I a * 5 «.£ X „ •o E • * si li M E •& & 3 0 -o • 3 « P 0 C £ a a -55 11! Il| 1 Prolong confinei Control contami oc 5 58 Hi fc-^ CC OS" UJ