To use Figure 2-1, place a hairline from the point of the right hand
scale, representing the nuclear burst angular cloud width at 5 minutes
after detonation, through the point on the center scale representing
flash-to-bang time or distance to ground zero.
At the point of
intersection of the hairline and the left hand scale, read the yield
where the hairline crosses the yield scale.
For example, a plot of designated observer positions and reported
azimuths have been made.
Observer A reported a nuclear burst angular
cloud width on line item LIMA at 280 mils. The distance between observer
A and GZ is 21 kilometers. To estimate the corresponding yield by using
the figure, use a hairline to connect 280 mils on the right-hand scale
with 21 kilometers on the left-hand scale, read a yield of about 50 KT.
Distance in kilometers to GZ from observer using the
Polar Plot method is obtained by multiplying the
flash-to-bang time (Line J) in seconds by 0.35; or
it may be read directly from the center scale of
b. Stabilized Cloud-Top Height or Cloud-Bottom Height.
If cloud width or angles cannot be measured, the use of tactical aircraft
may be justified for measuring the cloud-top or cloud-bottom height.
Cloud-top or cloud-bottom height, when stabilized, can be closely
measured by a pilot in USAF, USN, or USMC jet aircraft. Figure 2-2 is
used by the NBCC to correlate these measurements with yield. The extreme
left and right scales on the figure are yield in kilotons, KT, or
megatons, MT. The scale second from the left is the cloud-top height at
H + 10 minutes in thousands (103 ) of meters or feet. The scale third
from the left is the cloud-bottom height. The other scales are not used
in yield estimation, but in fallout prediction.
To use the figure, determine stabilized cloud-top or cloud-bottom height
from line item MIKE of NBC 1 Reports or as reported by pilots through
liaison officers. Place a hairline directly over the reported data and
pin the hairline to the nomogram. Pivot the hairline until it crosses
the outside yield scales at the same value. This value is the estimated
EXAMPLE: A cloud-bottom height of 21,000 feet has been reported.
estimate the corresponding yield, place a hairline on the mark (21)
representing 21,000 feet on the third scale from the left.
hairline and pivot it about this axis until equal values are read on the
extreme left and right yield scales. Read a yield of 10 KT.