EY EY
FSRaROY
F
es
2
FS
2>
.
Bs
1
&
. i
es
a given measured value of AP/P,, the way in which the average sound velocity is defined is not
particularly critical when only moderate accuracy is required since c varies by only 14 to 15
per cent between sea level and the tropopause. For the present purpose & is taken to be
-
(z)
z-h
[ret
(A.3)
where z is the altitude of the gauge and h is that of the bomb. This function has been computed
from the meteorological data for each shot by aumerical integration.
The effect of wind has been taken into consideration by adding to the average shock veloc-
ity the average component of wind velocity, Wy, projected onto the line from shot to gauge (assumed to be along the flight path of the dropping aircraft). Since the wind component represents
only a relatively small correction to the average shock velocity, the way in which the average
is defined is not critical. In the present case the average has been computed by weighting the
wind velocity in each small incrementin altitude in propostion to the time that would be taken
by a sound wave in passing through the given increment of altitude.
The numerical values used in the computation of slant ranges are tabulated in Tables A.l
and A.2.
Since this procedure for computing the slant ranye assumes rectilinear propagation from
source to gauge, with the normal free-air decay of peak overpressure with distance, it is
strictly applicable only to the direct shock in the reg‘on of regular reflection or to the case of
a surface burst, where the direct and reflected shocks coincide from the start. However, at
points that are not too close to the triple point and at distances large compered to the height of
burst, the peak overpressure in the Mach stem does not appear to differ greatly from that which
would result from a surface burst; therefore the present method should give a reasonably good
approximation for the slant range in such cases also. Since the canisters that fell ii the Mach
region on King shot were all far from the path of the triple point, the slant ranges computed
Table A.1—AVERAGS SHOCK VELOCITY, MIKE SHOT
‘
;
F
z
Hi
k
Canister
No.
SP/P,
V/t
t, ft/sec
V, {ft/sec
Wp, ft/sec
V+We
2
3
4
5
1
8
9
0.929
0.861
0.138
6.088
1.919
0.515
0.212
2.398
2.324
1.358
1.273
3.235
1.988
1,492
1118
1117
1114
1110
1128
1126
1127
2681
2596
1511
1413
3649
2238
1681
-17
—18
—22
-22
-17
~19
—20
2664
2578
1489
1391
3632
2219
1661
10
11
0.0656
OAM
1.199
1.300
1120
1120
1456
~21
-21
1322
12
0.0341
1.119
1113
£245
~22
1223
1343
1435
from the travel times to these canisters are considered to be sufficiently accurate for the purpose of this report.
In Project 1.1 of Operation Snapper, Shot No. 8, the slant ranges were deter’-‘ned both
from travel times and by an electrcnic multiple-object tracking systém (MOTS). The percentage difference between the MOTS and travel-time ranges had a root-mean-square value of 3.6
per cent and an algebraic mean difference of 2.2 per cent, the travel-time ranges being the
larger on the average.
i
Bed Sete DAraeaEeeeok
\
42
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