and amplitudes was uncertain. The air-induced signal propagated with a velocity of the air-blast wave,
decreasing with increasing ground range, while the
ground-transmitted shock propagated with a velocity:
radiation exposure is of little significance at distance;
beyond 16,000 fect for surface burstg of yieids up to
of about 8,700 ft/sec. The determination of velocities
and displacements by means of integration of the acceleration traces was not aftempted—the precision
of the data was too poor to support such an analysis.
Project 2.2 “Gamma Rate versus Time” (WT-913).
Project 1.8 “Dynamic Pressure Investigation”
Signal Corps Engineering Laboratori2s; Peter Brown,
(WT-911), Ballistic Research Laboratories; E. J.
Bryant, Project Officer.
The objective was to evaluate dynamic pressure as
a damage parameter.
Project Officer.
In addition, some information
regarding the damage effect of long positive-phase
duration was to be obtained. A total of 27 jeeps were
exposed on Shots 3 and 6; the ground ranges were
selected to obtain dynamic pressures comparable in
magnitude to those acting upon the jeeps experiencing
light to severe damage on Shot 10, Upshot-Knothole.
The yield of Shot 3 was too low to give any significant results. The limited results of Shot 6 were not
conclusive enough to permit an evaluation of dynamic
pressure as 2 damage parameter to be applied to the
jeep as a drag-sensitive target. Further, the results
did not allow a separation of the effect of dynamic
pressure on damage from the effect of the long
positive-phase duration. Based on a comparison of
Castle and Upahot-Knothole data, Project 1.3 proposed
cube-root scaling for vehicle damage. However, a
composite AFSWP report, TAR 514 “Damage to Military Field Equipment from Nuclear Bursts” was sub-~
sequently prepared which included the Castle, UpshotKnothole, and all other nuclear-test data. This
report concluded that W’-“ scaling was the most ap-
propriate method for predicting damage to military
field equipment.
PROGRAM 2: NUCLEAR RADIATION
STUDIES
Project 2.1 “Gamma Radiation Dosimetry”
(WT-912), Signal Corps Engineering Laboratory;
Robert Dempsey, Major, USA, Project Officer.
The objectives were to document the in‘tial end
residual gamma radiation exposure from high-yicid
bursts in order to assist in the evaluation of the resultant gamma radiation hazards, provide data for
the correlation of results for other projects, and extend the use of gamma-~radiation dosimetry techniques
to higher gamma-exposure ranges.
Radiation exposure from a series of nuclear detonations was measured by photographic films and
chemical-dosimetry vials of various sensitivity
ranges. The film and chemical detectors were placed
in protective detector stations at positions from 1 to
15 miles from ground zero for Shots 1, 2, 3, 4, and
6.
15 Mt, iz) the decay rate is affected by the capture
products of the thermonuclear devices fired, and (3;
the initial-gamma- radiation spectrum for Shot 3 appears harder thanthat obtained from fission devices.
Calibrated exposure range of dosimeters used ex-
The objective was to document the gamn: ~radiation
rate from the detonation of high-vield thermonuclear
devices. Two types of measurements were nade:
(1) initial-gamma rate versus time at various fixed
distances from ground zero and, in particular, the
effect on the initial-gammarate due to the passage
of the shock from ground zero through the detector
station, and (2) gamma-radiation time-intensity datz,
which gives information on fallout rate of arrival and
gamma-field radiation-decay rate during the period
up to 36 hours after the detonation.
Ali measurements were made using scintillation
detector techniques. The instrument stations were
self-contained and required no outside facilities other
than timing signals to turn the stations on at a predetermined time prior to the detonation.
The expanding firebull and the passage of the shock
front from ground zero through the detector station
had a marked effect on the initial-gamma rale and
hence on the integrated expesure. In general, the
inittal-gamina rate decreased relatively slowly after
reaching its peak value immediateiy after the detonation, began to rise slowly, and then rose rapidly to
the same value as the peak received at time of detonation. After reaching the second peak vaiue, the
rate decreased rapidly toward zero value.
Theinitial decrease in rate was attributed to the
natural decay of the fission products, the slow rise
to the expanding of the fireball and approach of the
shock front, and the rapid rise to the passage of the
shock front through the detector station. These effects were also evidenced in the integrated exposure
prior and subsequent to the arrivai of the shock front.
The average velocity of the shock front was found
to vary with distance from ground zero, decreasing
rapidly with distance.
The decay exponent from the residual contamination and fallout was found to vary with distance and
direction from ground zero. In general, the decay
exponent appeared to increase rather abruptly several
hours after the detonation. Thie can be attributed to
the presence of short-lived isotopes in the residual
contamination and fallout.
In general, it was indicated that the magnitude of
gammaradiation emitted from high-yield thermonuclear devices is considerably lower than the predictions in the Super Effects Handbook (Reference 11).
tended from 1 to 60,000 r.
In general, it was concluded that (1) initial-gamma-
108
At approximately 2,390-yard range, this handbook
indicates the exposure from initi:' gamma from a