of a Surface Detonated Nuclear Explosion” (WT-922),
terially increased, and the reliability of craterprediction methods formulated therefrom was improved. Based on the crater data from this project,
as well as a considerable amount of high-explosive
and other nuclear crater data, the handbook “Cratering
From Atomic Weapons,” AFSWP-514, dated 29 June
Bureau of Ordnance, Department of the Navy; James
Murphy, LCDR, USN, Project Officer.
The specific objective was to determine the effets
of a surface detonated nuclear device on a planted
sea minefiéld. Operational considerations limited
1956, was subsequently preparcd.
participation of the project to Shot 4.
The sea minefield in this test was laid in seven
rows disposed at ranges from 2,000 to 13,800 feet
from site zero. Except for Row 6 and two surfacelevel Mk 6-0 mines in Row 4, the mines of a given
row were laid on the bottom and were linked together
Project 3.3 “Blast Effects on the Tree Stand”
(WT-921), U. S. Forest Service; W. L. Fons, Project Officer.
The objectives were to: (1) determine blast damage to trees in terms of stand breakage, branch
breakage, and defoliation, where effects are influenced
by their location in a natural tree stand; (2) determine
the effects of natural forest coverage on attenuation
of the shock wave, in terms of peak overpressure
and peak dynamic pressure; and (3) obtain individual
tree-breakage data in the region of long positivephase duration, in order to substantiate the basis
for breakage and blow-down prediction.
The availability of the natural tree stands in relation to detonation sites and expectel yields Limited
this project to observations of natural tree stands on
Uncie, Victor, and William Islands of Bikini Atoll.
Participation was originally planned cnly for Shot 3,
but data was also obtained from Shot 1 becauseof its
unexpectedly high yield.
The principal tree types available for observation
were: (1) Pisonia, a tree resembling the American
by 230 feet of doubled 1!4-inch cable extending be-
tween mines.
Each string so formed was anchored
by a 2,000-pound cast-iron block attached tc ie string
by 1.000 feet of doubled cable. Heavy wooden buoys
‘vere used to mark the locations of the anchor blocks.
In Row 6 the mines were moored individually at depths
of 30, 50, and 125 feet.
Postshot recovery was done by reeling in the
strings of each row. In some instances this procedure
resulted in case damage to the mines. The moorud
mines in Row 6 and the string of Row 1 were lost und
never reccvered. In addition, mines closest to site
zero that were recovered about 24 hours after snot
time were radioactive, with an exposure rate of 10
r/hr.
Although only a limited number of mines were ex~
posed, it was concluded that a surface-detcnated nu-
beech tree; (2) Coconut Paim; (3) Tournefortia, a
broadleaf species of large shrub-type which were
chiefly under cover in Pisonia and Palm groves; and
(4) Scaevola, a large, low, green bush-type species.
Instrumentation consisted of snubber tree gages
(a simple device for measuring maximum tree deflection), a limited number of self-recorcing, static,
overpressure-versus-time and dynamic-pressure~
versus-time gages installed by Project 1.2b, and
extensive preshot and postshot photography. Staticbreakage tests of representative trees were also
made prior to the shot.
The distances involved were from 62,000 to 76,000
feet from ground zero for the inadvertent participation
on Shot 1 and from 3,000 to 31,800 feet for Shot 3.
Ground-level pressure measurements 2,000 feet into
a tree stand substantiated the Upshot-Knothole conclusion of no attenuation in peak overpressure. Since
for the first time natural tree stands were subjected
clear weapon was not an efficient method for minc ficid
clearance.
Project 3.5 “Blast Effect on Miscellaneous Siruc-
tures” (WT-901), Armed Forces Special Weapons
Project; Wayne J. Christensen, LCDR, CEC, USN,
Project Officer.
The objective was to documcnt damageinflicted by
Shot 1 on structures that had been erected fer utilitarian purposes in connection with the test operations.
This project was not in the original program, but the
unexpected structural damage which resulted from
Shot 1-—with its yield of 15 Mt approximately three
times that predicted— warranted documentation of all
the data possible about structural blast damage from
high-yield detonations.
It became evident from this survey that the effective lethal range to a light wood-frame building was
amazingly great for a high-yield nuclear blast. This
type of structure was damaged severely beyond a
range of 14.5 miles.
to a nuciear blast, the breakage prediction on American and European broadleaf tree stands can now be
Even reinforced-concrete
shelter-type structures as far as 14-mile range which
were exposed directly to the blast were vulnerable.
The islands of Oboe and Tare werethesite of a
made with a fair degree of confidence. Observed
damage from two devices of different yields compare
favorably with TM 23-200 (Reference 7) isodamage
curves prepared for broadleaf stands. Damage in
broadleaf stands is principally limb breakage and defoliation, with o¢casional breakage of the main stem
camp for approximately 1,000 persons, the shipping
center for all inter- and intra-atoll shipping, the
basefor all construction operations in the atoll, the
site for one of the later detonations of the test series,
or uprooting.
Project 3.4 “Sea Minefield Neutralization by Means
112
and the site of an air strip with minimum aircraft
servicing facilities. It had been intended to continue
to base operations on this island up to the last shot,