There is an uncertainty in ecal.ine :ccaetion wich involves whether the thermal yield is proporticnal t radi¢ bemical viet ® or proportional Ir, this paper, the thecretical to some lower power such as i of, upper limit is assumed and this in itself may give values 2 ix 7 times higher than actually obtaired. Tasr is aleo an uncertainty regarding the transmission of sir, because tna fireball rises raplidig tc great heights. Near the surface cf th: water, traneniesicn is quite low, but several hundred fee* above rhe water the trenmsmissicr. increases merkedly. The transmission ass..ed here is for very clear air and considered reasonably cafe. Although Liuge:ab is several hundred feet, below tit horicar at Eniwetos, ne protection is afforded from thermal radiation besause the firebal” rapidly g-iws tc @ diameter many times this value. A distinctive feature of the tinsrmal radiation on this explosion will be the long time ecales involved, marly 10 tims that from « & KT bomb. It may be possible te see the Light minimum and ths subseouent increase to maximum radiation, around 2 seconds. The thermal radiation will persist for soma 30 saconds instead of the 3 seconds fer conventional size weapons. Personnel sheuld be warned tnat it is necessary to keep on the dark epcpzgkesa for muth lenger péricds off time than for conventional size weapons. 3.2 TotaX Thermal Radiation vs Distance Figure i0 shows the total thermal radiation in calories tin” as a function of distence from ths bomb, These curves have heen derived using the assumption that the tetal thermal radtatian wilt represent 1/3 of the total yisid. The dotted Lincs represent the values of tota: thermal radiation which would be received if ons completely neglected absorption of thernai radiation by air. The full lines are based on a transmission of £5 per cent oer mile,, and corresponds to a very clear atmoarhere The fui lines are considered reasonable estimates for strutiures near the ground. The dotted lines are an exagrerated upper Limit, more e.prepriate to high flying aircraft, 303 Temperatures of Surfates niposed to Thermal Radiatian. Both the "affect of Atomic Weapons" and "Capabilitias of Atomic Weapons" contain tables wiich give the critical energies in calories! em’ for a number of common materials euch as wood, loth, rubber, and piasties. The long duration cf thermal radiation of this weapon haa the effect of lmreasing these critical energies by a facter of 3 above the critical energy required en a conventional size weapon. Tne total thermal radiation occurs over lenger periods of time, this permits correspondingly longer periods for heat to be conducted away from the surface and into the interior of their radiated object. substances which are not shown in such takes the average surface temperature may be estimated roughiy from the following equation: Fer