Submarine Cargo Ships and Tankers 371 
the results of full scale trials, it is now possible to determine stability criteria and to 
design and use automatic control systems to suit the stability and the response of the sub- 
marine. For such large submerged tankers as those under discussion similar investigations 
would have to be carried out and would, in fact, be vital since the margin of safety involved 
in terms of time and the depth range is obviously much smaller. 
On the question of structural design it is fair to state that the unpressurized structure 
which may contain liquid cargo offers no insuperable design or constructional difficulties, 
but, as Dr. Todd points out, it is indeed a grave assumption that it could be of light scant- 
ling. On the other hand the problem of designing the pressure hull and the consequences 
which could result from the application of incorrect principles are much more serious. 
Sudden collapse of the hull can arise from elastic failure of the structure or plastic failure 
of the material, so that the problem involves not only the theory to avoid one or both of 
these but also the development of special steels. This development work becomes more 
and more difficult as the thickness of the steel increases, i.e.,as the size of the pressure 
hull increases. Construction of the pressure hull is a highly specialized technique. Not 
only must the hull be built to a small degree of ovality, or “out of circularity,” but it is 
necessary to employ highly specialized welding techniques. Local weaknesses brought 
about by poor design or bad workmanship introduce a danger factor since they could lead 
to early local failure and sudden collapse of the hull. 
Merely to emphasize the vital nature of these two problems of stability and strength let 
us take Dr. Todd’s example of a submerged tanker 800 feet long with a pressure hull say 
600 feet long and a collapse depth 800 feet. Let us also suppose, as he does, that the 
tanker is proceeding at about 30 knots at 400 feet depth in order to gain the advantage of 
not generating waves, and then let us suppose that for some unforeseen reason it takes on 
a bow-down angle of 10 degrees for just 40 seconds. In that short space of time the fore 
end of the pressure hull would have exceeded the collapse depth and complete disaster 
would follow. It is as well to stress that this is by no means a hypothetical case but a 
real possibility. 
It is for such reasons as those which I have attempted to emphasize, and many others 
which Dr. Todd has mentioned, that I incline to the opinion that, although the possibilities 
of submarine tankers as cargo vessels for commercial use present a great challenge to the 
naval architect and marine engineer, there are many equally challenging and important 
aspects of surface ship propulsion which require our immediate and undivided attention in 
the near future. Not the least of these is the design and construction of hull forms capable 
of maintaining higher speeds in rough weather. 
F.H. Todd 
Mr. Newton rightly points out that the relative merits of the surface and submarine 
tankers in the matter of power depend very greatly upon the values assumed for the ratio of 
deadweight to displacement, and stresses that only detailed design calculations can give 
reliable guidance on this point. At the time of writing this paper, no such data appeared to 
be extant, but recently the results of such detailed weight estimates have been published 
in the U.S. by Russo, Turner, and Wood.* Detailed designs have been made for a number of 
submarine tankers with nuclear machinery having streamlined, body-of-+revolution hulls, with 
* Vito L. Russo, H. Turner, and Frank W. Wood, “Submarine Tankers,” Society of Naval Architects 
and Marine Engineers, New York, Nov. 1960. 
