SEAREP The various alternative programs presented in the event of "success" or "failure" have been considered by the Labora- tory from the point of view of endeavoring to maximize the position of the country both in bomb fundamental physics, and in present (or near future) stockpile position. We have placed . more emphasis upon understanding the behavior of nuclear explosions, and less emphasis upon certain practical details such as the minimum usable initiator strength. The latter point is covered, however, in the event that no "failures"occur by the proposal to include in the final shot two factors of interest: _Ll. A U-235 weapon with a smaller amount of active © material which will-give us very useful design information, and : . 2. An initiator of the present minimum acceptable strength. We are led to this position by the fact that no atomic weapon has yet been detonated with other than the strongest available initiator, and by the belief that our present lower limit, in which we have full confidence, should, nevertheless, have a practical test. We shall plan upon this program for the Sandstone Operation unless specific instructions are received to the contrary. Such instructions, in view of the time scale involved, can probably only involve changes in firing order of weapons now designed, or nearing final design, and. for proper planning, must be received before. January 15, 1948, It is quite impossible to incorporate any major design change in this test even if such instructions were received immediately. - Yours truly, /s/ N. E. Bradbury Director

Select target paragraph3