Semisubmerged Ships 541 
Before discussing control problems, it is important to consider in what way this craft 
would be better than a submarine. The question is, why should we take the trouble of hav- 
ing a strut piercing the surface, paying the penalty of additional resistance? In short, why 
not use a submarine? The answer is, for the moment at least, that there seems to be no 
doubt that the weight and size of nuclear power plants are greatly in excess of air-breathing 
plants of comparable power. In fact, the weight and space requirements of the present type 
of nuclear power plant seem to be two or three times as great as air-breathing plants. Fur- 
thermore, we have seen definite possibilities that the weight of air-breathing power plants 
can be further reduced. One of the most helpful developments here is the hydrofoil craft 
which, regardless of its own merits, is certainly stimulating the development of lightweight 
power plants that would make the air-breathing submarine even more advantageous. 
Because the high-speed near-surface craft with surface-piercing strut (semisubmarine) 
has not been previously discussed in the literature and because of the many interesting 
technical problems associated with this type of ship, the balance of this paper will deal 
with this particular craft. 
The appearance of the semisubmarine might be roughly as shown in Fig. 10. It would 
have a submarine-like hull, but not designed for high hydrostatic pressures. The strut 
would have to go high enough above the surface so that the crests of the waves would not 
cause difficulty. Its main function would be to take air down into the hull and carry exhaust 
gases out. It would be necessary to accept from the very outset the need for control devices, 
for we cannot expect it to run at a constant depth below the surface, even in calm water. 
The reason for this is, of course, that there are surface interaction effects. Any body mov- 
ing at high speed, or even at moderate speed, below the surface experiences forces (which 
can be resolved into a moment and force) related to the wavemaking on the surface. These 
forces probably reach their maximum at the condition of maximum wavemaking resistance, 
but they are still present at very high speed. Fortunately, the effects at very high speeds 
appear tentatively to be generally favorable. To explore this problem at the Davidson Labo- 
ratory, simplified linear equations of motion have been set up and solved on an analog 
computer. 
Fig. 10. High speed semisubmarine 
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