where:
R
t
5S
Cd
=
=
=
=
strength/drag ratio
thickness of wire, inches
ultimate stress, psi
drag coefficient
'
The wire used had a thickness of ¥, inch and an ultimate strength of 260,000 psi and, hence
a strength-to-drag ratio of about 32,000. In order to obtain the same geometry using a common
wire rope with an ultimate strength of 125,000 psi, the diameter required would be more than
Y inch, the total weight of the installation increased by a factor of 5, and the mooring limited
to a depth of about 2,200 fathoms.
The configuration of the mooring can be determined graphically for any set of conditions.
This permits the determination of total excursion, depth of submersion of intermediate float,
stress, etc.
An example of such a graphical configuration is shown in Figure 4.3.
It is apparent that one of the problems of taut mooring, that of the high stresses in lowering,
could be ameliorated by the use of a mooring line whose density was closer to unity. Some
suitable material eventually may become available, and SIO is investigating the use of a spun-
glass lines impregnated with flexible plastic.
Nylon line cannot be used for taut moorings be-
cause of its extensibility and its low strength-to-drag ratio.
The submerged float cannot be
permitted to surface nor to descend to more than about 500 feet. Hence, the uncertainty of the
dimensional stability of the system cannot exceed about 250/15,000 or about 2 percent. Nylon’s
extensibility and creep exceeds this by a factor of 20 to 40, a large part of which is unpredictable,
4.4 OPERATIONS
Initial plans called for the installation of sixteen stations to be anchored within a 30-mile
radius of the average geographic surface zero and in the area of expected fallout north of Bikini.
Figure 4.4 shows the geographic location of these stations for Shot Cherokee. The details of
description, operation, and installation of deep-moored instrument stations are covered in
Appendix B.
4.4.1
USS Sioux.
The ship assigned to this task was the USS Sioux (ATF 75).
Certain modi-
fications and installations were necessary before the ship could be used. A hydrographic winch,
a work platform, a ramp on the stern for use in retrieving the instrument skiffs, and all allied
equipment necessary for the installation were installed aboard in San Diego prior to the ship’s
departure for the EPG.
4.4.2 Initial Installation. The instrument skiffs were shipped to Bikini, and the instruments
were installed thereon at the staging area at Site Nan. As soon as two or three of the instrument
skiffs were completely outfitted, they were placed aboard the Sioux and taken to the mooring area
north of the atoll. There, at the predetermined geographic positions, the deep moorings were
installed, and the skiffs were attached to these moorings.
During the initial installations, none of the fallout instrumentation was armed. A few days
prior to the first shot, the Sioux made a trip into the area and all of the instruments were armed.
4.4.3 Maintenance of Instrument Skiffs. Between subsequent shots, the procedure for recovery and rearming the instrument skiffs was as follows:
The Sioux approached the nylon painter, which led from the instrument skiff to the subsurface
float. The painter was picked up well ahead of the skiff, the skiff detached. Another skiff with
instruments armed was then attached to the painter leading from deep mooring and launched
from the fantail of the Sioux. The time required to make this exchange was 15 minutes. The
detached skiff was then pulled up on the retrieving ramp and decontaminated, if necessary. It
was then brought aboard, the instruments recovered or the data recorded, and the instrument
skiff completely readied and rearmed to be launched as replacement for the next skiff recovered.
Occasionally, the instrument skiffs broke away from the moorings. In this case, a complete,
96