eet. Blast Mtg Notes, 29 Dec 51 The critical region seems to be from 20 psi down to about 7 psi. Disagreements are almost a factor of three in this region. This is again applicable to the question of post-detonation - pre-shock measurements, i.@., What happens to the air after the bomb goes off and before the shock hibu itt Before the shock ever comes along there is dust over the ground and absorption by thermal radiation. Porzel said that one could not measure the dust in the air before the shock arrives by measuring density, because the change is only a fraction of a per cent--although it still may have « significant effect in absorption. He thought that for this determination one should measure the temperature rise. Various methods for doing this were discussed. was Suggested that NRL-Stewart might be asked to measure ture and air absorption both on Ivy and Snapper. It pre-shock tempera- Both air temperature and density enter into the shock equations, but it Was suggested that sound velocity enters even more directly. It was thought that this could be measured rather simply in the pre-shock period, and it may be in some cases the parameter of most interest. (Whitener is working on an acoustic interferometer for use in measuring the afterwinds conceivably this could get sound velocity as well.) The question was raised: if sound velocity measurements are made, does One also want to know the density or temperature? Whitener thought the firet would preclude the latter only if the equation of state of the gas is the same after detonation as before, and one can say this situation is governed by the ideal gas laws. If this condition does not apply, then the sound Velocity measured may not give yP/p, which is what cne wants. However, in any dase, one needs to know sound velocity in this perturbed region containing dust and air. The important question in all this is, of course, whether these effecta=-dust, temperature changes, etc.--change the shock pressure. Ogle asked that before any decision was made, Porzel and Zadina look more thoroughly into this to decide just what factors are pertinent, and whatever they are, that We measure them at at least a few points. Zadina emphasized that this must be done before Snapper, anyway. The stations indicated on Table I were chosen for measurements of the parameters decided to be important. The positions were picked for regions of interesting pressures, and in addition, there are already structures on Bagebi and Aomon which can be used, As noted above, NRL will be asked if they Can measure temperature and air absorption; the responsibility for sound velocity and density will belong to Sandia and/or J-10. “RAE: