Submarine Cargo Ships and Tankers 357 
would have to be modified, in particular by moving the maximum diameter further aft, and 
this would increase the form drag. The hull would have to have certain fittings like conning 
tower, bow planes, flooding holes, anchors, etc., and no matter how these might be housed 
in recesses with covering doors, etc., they would inevitably act to some extent as turbulence 
stimulators, and the actual resistance would in fact be much nearer to the turbulent figure. 
While the idea of maintaining laminar flow is therefore extremely attractive, the practical 
difficulties of maintaining the requisite smoothness over the whole surface of a steel struc- 
ture of this kind immersed in salt water and subject to all the effects of corrosion and foul- 
ing present almost insuperable difficulties. Of recent months other devices to maintain 
laminar flow have been suggested, such as the use of a soft skin of rubber with liquid back- 
ing which would damp out the onset of turbulence and so prevent transition. Not enough is 
yet known of these ideas to be able to express any real opinion about them but they would 
certainly be expensive both to fit and to maintain and, unless they were immune to surface 
deterioration and fouling, it seems would soon lose their efficiency. 
COMPARISON OF SURFACE AND SUBMARINE SHIPS OF THE SAME DEADWEIGHT 
A considerable number of papers has been written giving comparisons between conven- 
tionally propelled and nuclear propelled surface tankers. These have shown in general that 
the nuclear propelled tanker cannot yet compete economically with one having conventional 
machinery unless the capital cost of the nuclear plant and the cost of nuclear fuel become 
considerably less than their present values. This paper is not concerned with the relative 
merits of conventional and nuclear machinery, but since the submarine cargo ship or tanker 
can only be contemplated on the basis of nuclear propulsion, any comparisons made are on 
the basis of nuclear machinery for both ships. In this way the weight of the machinery will 
be comparable in both cases and will therefore affect the deadweight available equally in 
each case. 
Several authors have given values of the deadweight/displacement ratio for nuclear 
propelled surface and submarine tankers, and values of this ratio are shown in Figure 8. 
Although there is considerable scatter in this diagram, it is considered that if we take a 
+++ SURFACE TANKERS 
© ©© SUBMARINE TANKERS 
ASSUMED RATIO FOR 
SURFACE TANKERS 
ASSUMED RATIO FOR 
SUBMARINE TANKERS 
) 20,000 40.000 60,000 80.000 {00,000 120000 
DISPLACEMENT IN TONS (A) 
Fig. 8. Deadweight /displacement ratios 
