3- The range over which these data mst be extrapolated in order to permit prediction of megaton craters is enormously greater than the ranges of extrapolation commonly accomplished in engineering or scientific fields. The situation is roughly equivalent to an attempt to predict the penetration of the projectile from a new anti-tank gun through armorplate based on observation of many measurements of the penetration of BB's from an air rifle through tin cans plus a few measurements of the penetration of .45 pistol bullets through pine. As a result of these facts any extrapolation procedure is inevitably associatedwith quite a large uncertainty in the final result. In making any extrapolation it is believed, consequently, that it is of major importance to indicate the order of magnitude of the uncertainty involved as well as the extrapolation itself. At the outset of any attempt to develop extrapolation procedures, one is faced with:a philosophical choice. On the one hand he may look critically into the mechanism of the phenomenon end on the basis of physical or, in this case, mechanical analysis, study the causes, the effects, and the influence of specific parameters. Alternatively, he may adopt the attitude Ahat, in a complicated phenomenon such as crater formation, the mechanismsby which causes and effects are interrelated are so illknown as to be for’ the moment, unknowable, and hence conclude that the appropriate approach.is the empirical extrapolation of the existing data into the range’of[parameters where prediction is desired. It is the author's opinion that the-second approach is the more realistic one under the circumstances involved in the present problem and that is the approach described in the és important deviation from past that cube root scaling is on this basis the extrapolation der of this report. The most casioned by this approach is discarded as a primary tool in and is used only for assistance in relatively minor aspects. In adopting an empirical approach, it would of course, be absurd to ignore the information, however meager; in regard to the physical mechanism and particularly in the distinction between the mechanisms occuring in TNT and in nucleer explostfons. On-'the other hand, it is believed that too much dependence on cube root scaling is likely to give the illusion of a precision in prediction unjustified by the facts. The development described below was undertaken within the framework that the desirable result from a military standpoint ig the construction of graphical or analytical relations such that."knowledge of the yield, soil, and depth will permit easy prediction of. the crater dimensions. It is postulated that the shape of a crater ‘for the craters of interest is primarily dependent on its size and-‘hence the first attempt is to predict crater radius in terms of the three parameters just mentioned, with the expectation that a later analysis can‘ve made to predict depth and other shape aspects once the radius prediction has been accomplished.