side of reality.
Since this unrealistic efficiency is paired with the
value m * 3.4, it is consequently likely that this value of m is algo
too high.
The procedure described for constructing both the TNT and the
nuclear curves shown on Fig. 4.3 can be performed equally well using
values of m other than the most probable value of 3.4.
Other appro.
priate values of mas indicated on Fig. 4.2 are 3.0, representing both
conventional cube root scaling and the lower limit of slope on the basig
of the;10 per cent uncertainty in experimental values postulated earlier,
and 4 representing the upper limit.
Both curves have been plotted
together dn:Fig. 4.4,
Since,: for military purposes, it is believed that the data for
extrapolation’ should be available in the simplest possible form for
quick use without: computation, the nuclear curves shown on Figs. 4.3
and 4,4 have been re-plotted in the form of radius in feet against
charge depth infeet, with yield as a parameter.
This has been done on
Fig. 4.5, in which for each yield shown both the most probable value
(m = 3.45 and the limiting values m = 3.0 and 4.1 are shown.
The estimates for this soil for the most probable value of m
(m = 3.4) are re-plotted on Fig. 4.6.
Range of uncertainty (m = 3.0
end m = 4.1) are indicated by short horizontal bars attached to each of
the parametric yleld curves.
The same kind of analysis has been carried through for dry clay,
dry sand, wet clay, and sandstone and the results of these analyses are
included in Figs. 4.7 through 4:10.
In the case of these other soils
no nuclear data are available and-hence the efficiencies found in the
Nevada soil have been used in thefollowing fashion. For the most probable value of the scaling exponent min each of these other soils, the
variation of efficiency with depth ‘at-Nevada for m = 3.4 has been used.
Similarly, for the lowest value of for each of these other soils the
same variation of efficiency with
dept:
been used as was found at
Nevada for the lowest value of m there,
ily, 3.0.
The corresponding
analysis has been made for the upper limiting value of m.
The most probable and limiting values of m for all the soils reported here are listed in the table below. In-each case, the available
data have been plotted in the same form as wag shown on Figs. 4.1 and
4,2, the best straight line was drawn for those-points and then values
of radius 10 per cent above and below the curve were marked at the upper and lower limits of the charge sizes considered..# By this procedure, the limiting values of m have the greatest range for those soils
in which no large TNT charges have been fired, and this is appropriate,
since in fact the extrapolation is less certain in such cases.
In the case of wet clay, Fig. 4.8, so little TNT data are avail~
able that crater radius has been predicted only for the most probable
value of the scaling exponent m.
Ro
# It vas decided not to review TNT data from charges less than 200 lb.
48