is a serious question, however, whether thin slabs are applicable to the 
MOBS mission requirements, which presumably will include the open sea. 
The low freeboard offers virtually no protection against deck washing, 
and it is extremely doubtful whether a floating breakwater can be developed 
which is effective in deep water against large ocean waves. The relatively 
low mass and large water plane area suggest that the thin slab will be 
closely coupled to the seaway and that platform motion, particularly 
heave, will be considerable. 
Platform with Pre-Tensioned Mooring Lines. This concept is a vari- 
ation of the semi-submersible platform. The platform (Figure 3.7) is 
first towed to the operational site in a shallow draft mode (to minimize 
drag resistance); then the anchor lines are deployed from each of the 
vertical buoyant support legs while water is added to the ballast tanks; 
and finally, the platform is emplaced with each gravity anchor resting 
on the seafloor. Hydrodynamic stability is due to several factors, the 
most important being: 
1. low water plane area, 
2. placement of the horizontal pontoons beneath the 
water surface where wave action is minimal, and 
3. the anchor lines, which are always in tension, 
prevent vertical platform movement. 
The platform depicted in Figure 3.7 is intended to serve as an oil 
exploration and development facility and, presumably, would be constructed 
from steel. There is no inherent reason, however, why concrete could 
not serve as the principle structural material. Recently, for example, 
Weidlinger (1970) described a composite steel/concrete floating airport 
which is anchored by taut mooring lines to the seafloor. Like the oil 
platform, most of the buoyant support is submerged to a depth sufficient 
to prevent excitation by the seaway. 
The disadvantages of using this concept for MOBS are twofold: (1) 
It would be difficult {and expensive) to deploy platforms in deep water, 
and (2) large platforms would require numerous anchors and mooring lines 
that will take time to emplace, as well as create a severe logistics 
burden. As a result, rapid re-deployment of the platform would be 
sacrified. 
CONCEPT OPTIMIZATION 
Crucial to any attempt at optimizing the base concepts for MOBS, 
viz. the elevated platform, semi-submersible platform and the barge 
platform, is a recognition of those parameters which characterize a 
candidate's performance. A complete listing of parameters would be long 
and an analysis of their effects time consuming and unwarranted due to 
the present uncertainty regarding the MOBS mission. Consequently, only 
a partial listing and discussion of the more important ones used in the 
preliminary design, will be attempted here. 
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