BUOYANCY SYSTEMS 
The ability to employ suitable buoyancy to support large weights In 
the ocean is probably the single greatest plus in working there over terrestrial 
locations. On the surface, simple open hulls are sufficient. At shallow depths, 
either a pressure-resistant hull or a filling material (probably air) at the local 
pressure of operation or higher must be used to prevent collapse. At succes- 
sively greater depths, either the pressure-resistant shell must be made stronger 
and heavier or the pressure of the gas must be increased. Spherical aluminum 
floats are used to a few thousand feet, at which point the shell thickness nec- 
essary is such that the net buoyancy is greatly reduced and the buoys are no 
longer economically attractive. Spherical and cylindrical shapes typically fail 
in buckling from instability rather than by compression when made of ductile 
materials. Nonductile materials and those of comparatively low strength per- 
form well over certain pressure ranges, particularly if the density of material 
is low enough to allow thick walls, which are stable against buckling. Glass is 
a particular case of a very strong, nonductile material which actually increases 
in strength when under compression over practically the entire pressure range 
to be met in the world’s oceans (Perry, 1963). 
While concerted efforts along the lines outlined above are being made 
under other assigned portions of the Deep Ocean Technology project and 
other ocean-related research and development tasks, it does not appear that 
economically feasible developments will immediately be ready for use. Because 
large volumes of relatively low-cost buoyancy materials capable of withstanding 
full ocean pressure will be needed to build an adequate low-ground-pressure 
chassis for soft bottom materials, a limited effort in development is outlined 
here. Features to be sought in order of their importance are: 
1. Low cost per unit buoyancy 
. Pressure resistance of completed buoyancy units 
Z 
3. Low density 
4. Ability to withstand rough usage as fabricated 
5 
Low thermal coefficient of expansion 
The so-called syntactic foams, in which very small beads of either 
glass or a strong plastic are embedded in a strong plastic binder such as epoxy, 
have been widely used in small systems and considered for at least one large 
application (Bechtel, 1965). They are good in factors 2 and 4, but are very 
expensive and marginal in density and expansion traits. Figure 42 (Bechtel, 
1965) illustrates the form and application of massive floats to a buoyancy 
system for lowering a nuclear reactor to the ocean bottom. 
53 
