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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,
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