water of acoustic pressure signals generated by high-yield detonations; (7) determine
water-wave phenomenain shallow water from high-yield surface detonations; and (8) determine ground accelerations at distances relatively close to surface zero for high-yield
detonations.
2.2
SCALE FACTORS
Air~pressure data were reduced to standard conditions — equivalent to a 1-kt burst at
sea-level ambient pressure and to 20 C ambient temperature.
rections were applied:
The standard Sachs cor-
14 7
Pressure Spy = >
oO
Py
Distance Sq =
1/3
as)
1
1/3
(=)
/ To + 273
Time St = { =a)
1/2
P,
ee
1/3
1
(=)
1/3
Where: W = yield of the device, kt
Py = ambient pressure at burst elevaticn, psi
T, = ambient temperature at burst elevation, C
Teble 2.1 presents the pertinent scaling factors used in converting the data to standard
conditions.
2.3
SURFACE MEASUREMENTS
The significant factor affecting measurements of the blast wave along the surface was
that all shots in the scheduled Castle series were surface bursts, either on atoll islands
or lagoon barges, with yields in the megaton range. Considerable interest had been
maintained in surface bursts; it was obvious that more-complete data was necessary to
improve the state of the knowledge. Safety consideration restricted full-scale tests of
even kiloton-range devices on the surface at the Nevada Test Site. It was hoped that
Castle would supply answers to questions on large-yield surface bursts.
Upshot-Knothole had confirmed the existence of the precursor, and while its fundamental mechanism was not fully understood, its effect on the various blast parameters
was quite evident. However, these were precursors from aboveground bursts. The
surface-burst intercepts of the height-of~burst curves were based on Jangie surface and
the Ivy Mike events as well as the Greenhuuse and Sandstone tower shots. Castle offered
an opportunity to check these data, as well as to investigate the possibilities of a precursor forming from surface bursts, even though it was recognized that Nevada precursors might not be duplicated under the EPG condit.ons of atmosphere and ground surface.
Upshot-Knothole also showed the fallacy of assuming side-on overpressure in the precursor region as a basic damage parameter to drag-sensitive targets. It was found that
overpressure and dynamic pressure were not affected in the same manner by the precursor: dynamic pressures were not only considerably greater than those calculated from
measured overpressure but were even greater by factors of two to three over those cal-
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