August 1959: | . reco - f?/ In the ongoing research and development effort for hish altitude detection techniques, the problem of discriminating between explosion phenomena and Lichtnins: effects seems to be soluble and a method of discrimination has been worked out and is being tested. The first lencthy discussion on the meneral subject of consealment of under:round explosions states "the consealment of nuclear explosions by containing them within underground cavities of a sufficient size to ensure the elastic be-~ havior of the cavity walls had been suggested. Many facets of the problem lend themselves to theoritical considerations and are presently beinz investigated. In particular, a theoritical analysis of the stress Cistribution existins at the surface of the cavity excised from an elastic solid has been undertaken. Expressions have been obteined for the "Zoop stress” exerted on the surfece of a spherical cavity in two cases of interest. In tne first case (considered jointlywith T-Division) an elastic half-spece from whiehthe cevity is excised, is acted upon by a gravatationel body force. In the second calculation a@ spherical cavity is excised from a region initially in a state of arbatrary stress. Calculations using the second enaliysis lead to a conclusion that an; inner cavity pressure arising from an explosicn cowl eceily, sive visu 2: solitting of the cavity vall would consectuernt exmission of a much Lercer sismic os sicnal than would be the cese if the wall behevec. elasvicall by J-Division. Data. analysis and calculations based on the Teak snot are con- tinuing at a significant level. By a 3 Aug. memo to DDR&E, the Chief of DASA adds another test to the tests ne . planned for Willow which already include high altitude tests and water surface and j 5 sub-surface tests. The new addition is a land surface weapons effects tests to be performed at the EPG.

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