Yield estimation is based on development of nuclear clouds. For yield
estimation purposes, nuclear cloud development has three stages. The (1)
fireball stage begins at the instant of detonation.
It will continue
until the cloud of explosion products ceases to radiate a brilliant
As this brilliant light fades into a dull glow, the cloud
transforms into the (2) nuclear burst cloud stage.
At this time the
cloud may be seen as a spherical cloud (high airburst) or a mushroom-type
cloud (low air or surface burst). Severe turbulence and rapid growth in
height and width are characteristics of this stage of development. This
stage lasts until the cloud stabilizes in height (4 to 14 minutes after
detonation). When taking cloud measurements, it is accomplished at H + 5
minutes or H + 10 minutes, with H as time of detonation. When the cloud
ceases to grow in height the (3) stabilized cloud stage begins. This
stage continues as long as the cloud is detectable.
Nuclear burst cloud measurements or parameters have been correlated with
yield and are presented in nomograms, each of which is an independent
means of determining an estimated yield.
Nuclear Cloud Parameters
If any of the following combinations of nuclear burst parameters are
known, an estimated yield can be determined from nomograms.
Distance to ground zero (or flash-to-bang time) and nuclear
burst angular cloud width (H + 5 minutes)
Stabilized cloud-top or cloud-bottom height (H + 10 minutes)
Distance to ground zero (or flash-to-bang time) and stabilized
cloud top or cloud-bottom angle (H + 10 minutes)
a. Nuclear Burst Angular Cloud Width.
The Nuclear Burst Angular Cloud Width nomogram (Figure 2-1) is used to
determine yield from nuclear burst angular cloud width measurement and
distance to ground zero (or flash-to-bang time). The right hand scale is
the nuclear burst angular cloud width in mils or degrees, the center
scale is the flash-to-bang time in seconds and the distance in kilometers
to ground zero, and the left hand scale is the yield in kilotons (KT).