wotTEs 3.3 DISCUSSION 3.3.1 Blast Overpressure The measured peak overpressures and slant ranges have been reduced to equivalent values in 2 uniform atmosphereat sea-level pressure and temperature by applying the Fuchs’ scale zactors defined by a(z) = em |" {Fey oy" [pao 1} “ u(z) (3.1) = A(z) [er 210) [zea Polz) (3.2) eee where T(z) and P,(z) are the ambient absolute temperature and pressure, respectivelv. These factors have been computed as functions of altitude by numerical integration of the Bikini meteorological data for the time of Mike shot. Since the meteorological data for King shot differed only slightly from that for Mike shot, the same values of A and » have been used in both cases. The fact that King shot was fired at an altitude of 1500 ft instead of actually at sea level has been ignored since correction for this factor would be entirely negligible. The computed values of A and p used are giver in Appendix C. According to the Fuchs scaling law the peak overpressureat altitude z and slant range R due to a bomb burstat sea level is given by AP = {(AR) (3.3) If the reduced overpressureis defined as AP/p and the reduced range as AR, Eq. 3.3 states that the reduced overpressure is a function only of the reduced range. The values cf AP/ and AR for Mike shot are listed in Table 3.6 and are plotted (circled points) in Fig. 3.7. The points indicated by triangles in Fig. 3.7 are preliminary readings of ground-pressure yauge measurements obtained by the Sandia Corporation and transmitted to the Air Force Cambridge Research Center (AFCIC) through the courtesy of E. F. Cox. The final results from Sandia Corporation on Project 6.1 are presented in WT-602.? For comparison with previous results, the following analytic expressions have been derived to represent the free-air peak overpressure in a homogeneous atmosphereat sea-level ambient pressure: __ 3,248 f(r) = (70.5858) Viog 2/0 3858) r<i1.5 ‘ r>1.5 (3.4) (3.5) weeme 1.564 1.964 3.071 {(r) =Ray tart where r = AR/W's, R being the slant range in kilofeet and W the yield in kilotons. It will be noted that these expressions differ somewhat from similar analytic formulas that have been used in previous reports on air-borne pressure measurements during Operations Jangle' and Snapper. The present forms give an improved fit to the Tumbler-Snapper results both in the region of i.lgh overpressures (Naval Ordnance Laboratory smoke-rocket photography) and at tow overpressures (AFCRC parachute gauges). The curve plotted in Fig. 3.7 is computed from Eqs. 3.4 and 3.5 for an effective yield of 24 Mt. This figure for the effective yield is the cube of the arithmetic mean of W% computed separately for each parachute-gauge data point. The ground-pressure gauge data were not used in this determination. Since, for a ground burst, 31 RESTRICTED cata - SECURITY INFORFAATION rs re XS ts m =