@ 4 an co © : 1104 The resulte are of interest because they tend to confirm the high yield ahown by the fireball. However, it is a reasonable question what the ef- sa a “4 eo 3. ] fective sound velocity really is; at ground distances like 100,000 feet the velocity at the “surface” 1s a microscopic detail, the shock propagstion is controlled by sound velocities at many thousands of fest. At al- tidude, the temperatures and wind velocities were such as to decrease the apparent sound velocity, increase the time difference and therefore spperent yield. For example, if at the dates (168,000 feet) sound velocity is taken as 1194 feet instead of 1130, to compensate for a 17 knot wind which was present from altitades of 2000 feet to 9000 feet, the acoustic time raises from 162.9 to 164.8 seconmis, the time difference raises to 15,9 seconds, and the apparent yield to about 12 MI. The sane value of sound relocity cecurs for an ambient temperature of 23°C, compared with 27°C as measured at the surface, oe 18.8°C a9 measured at 5000 feet. Sound velocity st the “bere ne ipa he a ag lille etry surface has meaning, only a6 related to the peak pressure as mangured at the surface, At the high pressures and velocity, the interactions buhind the shock wave and very repid and « low “averege axbient” sound velocity say at 5000 feet, my quiekly affect the shock velocities at distances like 15,000 feat, where pressures and velocities are still high. At large distances the yosk yeessures mangured at the surface are already low, presumbly becawe of ee Cont Sree coe atmospherics effects, the shock arrival times will be later, the apparent yield etill scmevhat consistently amall, Here again, the atmospheric effect is pro- bebly the significant factor, In all this, the theoretioal curves may be in error, of course, but if so, the close-in values of pressures would be encual- ously high. BEST AVAILABLE COPY Positive durations reported by Sandia Corporation are mich longer than predicted, and would iodtonte abnormally high yields, This result again my -6~ SNL ; : i : :