choice of some other rate of fall for tha particles,
From the test of the method
against the Bikini patterns, it was clear that it was good enough for the
purpose at hend.
It appeared that differences between forecast and actual
winds would be likely to produce much larger errors than those inherent in the
assumptions.
5.
In application, the method is not as tedious as right appear,
The standard
hodograph plot, giving the location of central particles falling at 5,000 ft
per hour, is prepared for the briefing as a matter of course.
It can be
superimposed on a ten tires magnified atoll map, allowing for the 50 ,000 ft per
hour fall rate assumed in the method.
With a ruler of corresponding scale,
the distances S, along the eig~sag path to each of the height points on the
hodograph ean be quickly measured or this can be done by summation of "hodograph*®
winds if these are more readily accessible. Likewise, the distances from the
altitude points on the hodograph to points of fall-out interest can be quickly
measured with the ruler, giving the values of r.
compute p and q.
Knowing S and r, one can easily
With the aid of a family of curves of
1 {a}
P
p*
2
vs q (see
Fig. 1) for several values of p, one can rapidly interpolate the values that
must be added up at any location,
The exponential factor drops off very
rapidly with q, and after working out a few cases, one can tell, from an
inspection of the hodograph-on-atoll plot, some of the altitude points that can
be neglected in the computation,
6.
Fig. 2 and Table 1 dllustrates the application of the method to NECTAR shot,
using the winds observed at shot time.
The points on Fig, 2 marked 10, 20, 30,
are the 10,000 ft, 20,000 ft, - — - altitude points on the hodograph for particles
falling 50,000 ft per hour.
A partiole starting, for example, at 30,000 ft
above ground zero, and falling under the influence of winds but not diffusion,
* would land at the point rarked 30.
" COPIED/DOE
+ LANL pe
The value of 8, the horizontal distance
Gj