among which are: (1) (2) R= f(W) . f(W, DQ) . t(m) R= f(W, m). t(Ws Dy )* In attempting to correlate crater data from TNT blasts with those from nuclear explosions, it has in the past appeared useful to include a factor less than unity (0.3 to 0.9) in the value of W assigned to nuclear charges in terms of equivalent tons of TNT, based on radiochemtcal data. This has been justified by the fact that the energy parti- tion|ds totally different for the two types of explosives and that the nuclear weapons deliver radiant energy while conventional explosives do not. It-is believed, however, that at best correlation will be uncer. tain, and:with the advent of megaton weapons the disparity of sizes is sO great; that good correlation should not be expected. #* The effect of charge depth (or height) (4,) is fairly well estab- lished for TNT. If scaled crater diameter is plotted against scaled charge depth, it is clear both from experiment and physical reasoning that the curvé will be concave downward, since no surface crater is produced if the charge is sufficiently high above the surface or suf- ficiently deep below it. For TNT, the maximum of this curve is rather broad and occursin the range of 1 < 4, <3, where 4, is in ft/(1b qt)2/3, The effect of the medium, f(m), has been shown to be as large as a factor of 2 in field experiments with TNT. Unfortunately, the specific properties of the medium: which affect the crater are not yet established. It is postulated that strength, either shear or tension, and density are sensitive parameters. It is possible that the elastic moduli are also important. In regard to strength, it is of course the strength under shock load conditions that is,Amportant. It is very difficult to make laboratory tests under shock*‘téad,-eonditions and the heterogeneous char- acter of earth makes the extrapolation from laboratory to field condi - tions very uncertain. Thus, whi ea propriate values for strength under shock load are not known, it appédr “tire that the strength under such conditions may differ widely from the strength under static load. The density of the medium may in ‘.‘enecretical sense affect crater size significantly. In practice, howe er, the range of densities found is trivial compared to the range of streéngths.and hence the density is believed to be a parameter of only minor ingrtance in affecting the crater. As has been mentioned, the application|:of similitude principles i| * The data at hand have seemed to the author to:fit better into an equation of Form (2) than into one of Form (1),! nanely R = (we) » £(%) these-two forms are It is to be noted that as-elaborated in Chapter 4. drastically different in the implications of extrepolatiog‘from less Lae than kiloton charges up to megaton charges. ** Thus Fig. 3.14 has been plotted with no consideration: of‘relative efficiency, while in Fig. 4.11 a relative efficiency of 60% for nuclear charges compared to TNT has been used. 16