THE ENEMY ATTACK For the purposes of this study a massed attack of high-altitude bombers is assumed. It is assumed that the attack may come over Canada and also approach both coasts directly. The raid size is assumed to be sufficient to successfully explode from one to four 10-Mt weapons on the targets under consideration. LETHAL RANGE The mortality coefficients vs distance of a 10-Mt weapon as used in this study are presented in Fig. 9. For comparison, mortality vs distance curves as used*by the Fcpa? and srr‘ are also presented. All three curves are based essentially on Hiroshima-Nagasaki data and have been modified to account for the longer positive-pulse phase associated with 1007-17 i+ 80 7 = =z W got ‘ ‘, \ ° \ \ % Fr #0 < * \ — a N* \ ob \ 0 ! 2 _ _ FCDA 10-Mt weapon i \ “en weapon in this study XN \, 0 T . weapon SRI 10-Mt \ a T with underground shelter . ‘ a. ! Mortality for 10-Mt weapon \ = re ee EE Ot aLNRRA Ret ane oe = ee ee ee yl \ * ee 4 6 l 8 ~, 16 py 12 14 ! 16 ! 18 20 DISTANCE FROM GZ, MILES Fig. 9 — Population Lethality Contours for 10-Mt Ground Burst high-yield weapons. The curve used in this study was the best approximation to Hiroshima data that would meet the purposes of the study; like the sri curve it has a region of 100 percent mortality to meet the requirements of cratering associated with ground bursts. Figure 9 also gives the mortality coefficients for populations in shelters with 3 ft of earth cover. The 100 percent mortality “plateau” extends to the limits of the crater and lip that would be created by a 10-Mt ground burst and then dropsoff at the same rate 18 ORO-R-17 (App B)