Conclusions reached in these studies with model experiments lend support 
to selecting the semi-submersible as the most serviceable. A properly 
designed semi-submersible module would have the dynamic stability inher- 
ent to the columnar platform and the favorable drag characteristics of 
the barge type for mobility. Unlike the columnar platform, the semi- 
submersible could be readily constructed with a propulsion system like 
the barge. All three lend themselves to prestressed concrete construc- 
tion methods. 
An investigation by Bechtel Civil Inc., San Francisco (Appendix E, 
Item 11) as to the feasibility of Floating Airports, revealed that a 
steel runway deck with supporting structure of reinforced concrete ap- 
peared to be the most acceptable alternative concept, considering cost 
and operational effectiveness. 
Based on the cited investigations of MOBS alternatives, the semi- 
submersible provides optimal desired system characteristics. This con- 
cept is configured by combining three-deck semi-submersible modules (300 
feet by 300 feet) having the lower two decks and supporting structure 
composed primarily of prestressed concrete including buoyant vertical 
legs and horizontal pontoons. The exposed top deck is constructed of 
steel designed to withstand live runway loads attributed to fully loaded 
C-5 type aircraft. This alternative also provides a favorable distribu- 
tion of structural mass within the MOBS platform. 
C-5 aircraft, designed for inter-theater strategic airlift, is 
indicated for deployment along with C-17 aircraft for intra-theater or 
inter-theater transport in response to the Generalized Crisis Scenario. 
Assuming the basic module dimensions of 300 feet by 300 feet and the 
required runway length for fully loaded C-5 aircraft as governing crite- 
ria for platform length, the MOBS configuration emerges as a 9,900- by 
1,200-foot airport afloat having lateral extensions for other required 
basing functions. 
The architectural renderings (Figures 1 through 5) are represen- 
tative of the ocean basing system characteristics desirable for military 
and strategic applications, peacetime diplomatic and, commercial needs. 
28 
