€ @ end one at 280 KT in Alaska. While these experiments are basic to PLOW- SHARE, the results would apply to the employment of atomic demolitions. -d. Hardened Sites Finally, more data are needed for the design of hardened sites and the protection from induced electrical currents generated by surface or near surface bursts. Experiments are not yet designed, but to acquire the most useful information would require experiments involving construction in geological media characterfatics of our hardened sites. Some preliminary information on structural response will be developed from the planned HARDHAT experiment, which will be 5 KT underground in granite at the Nevada Test Site, and is scheduled for early 1962. Aa a final point, it should be emphasized that even for the weapons development program, particularly in the critical months ahead, the United States does not possess enough underground sites to meet all of thie urgenttest needs. By having the option of some surface or above surface tests, and by avoiding too conservative a policy with respect to venting, a greater rate of progress can be achieved. (Venting limits should be related to levels of off-site contamination such as meet public health and safety standards). Once the present lack of readiness and backlog of test requirements have been overcome, it would probably be possible, assuming a large investment in facilities, to carry out an adequate program at a satisfactory rate underground except for the large scale tests. There may, however, be unforeseen obstacles which could make this more difficult than now anticipated. For example, our first underground shot in the present series gave a greater yield than expected; some of the diagnostic data were ‘Lost; and what was more serious, an unsuspected underground / See y pa a

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