208 THE SUBMARINE OF TO-DAY AND TO-MORROW. 



Taking up first the remaining primary military features, viz., submerged 

 radius, surface speed, and surface radius, we are confronted first by the fact 

 that on account of the necessity for separate power plants, other things being 

 equal, an increase in any one of these qualities can only be obtained by a sacrifice 

 in one or both of the others. Keeping in mind the fact that a submarine on the 

 surface has only a minor military value, it is natural first to set some reasonable 

 minimum on the submerged radius. While opinions may well differ on this sub- 

 ject, the author holds the view that a radius of at least lOO miles at a speed of about 

 5 knots is necessary. This requirement by itself will not raise the minimum dis- 

 placement figure above mentioned, viz., 250 tons, and will permit of a surface 

 speed of from 11 to 12 knots, with a fuel supply corresponding to a radius of 1,000 

 miles. 



Leaving aside for later consideration the question of the "efifective" radius 

 of action, which, in fact, involves much more than the mere fuel supply, let us briefly 

 consider the effect on displacement of increasing the surface speed only. We have 

 only to remember the intimate relation of length to speed to see at once that, while 

 keeping the submerged qualities constant, increases in surface speed are expensive 

 in displacement. Thus to increase the speed of the above primary design by 2 

 knots, it is necessary to increase the length from 115 to 145 feet and to increase 

 the surface displacement from 250 to 325 tons, and an increase to 20 knots surface 

 speed would involve a length of about 260 feet and a displacement of about 1,000 

 tons. 



Increases in radius of action, in so far as the mere ability to carry the neces- 

 sary fuel is concerned, do not make such great demands on displacement, but when 

 all of the factors which in practice fix the "effective" radius are taken into ac- 

 count, the demands on displacement become astonishingly great. The "effective" 

 radius is in fact that distance which the boat can run on the surface, taking the 

 weather and sea as it finds them, and still arrive at its destination with the personnel 

 in efficient physical condition for submerged work. In other words, habitability 

 and seaworthiness from a habitability point of view are vital factors, so vital in 

 fact as to warrant some detailed examination here. 



In the case of the 250-ton primary design above referred to, about four days 

 would be required to run out the fuel radius. Good practice then would require 

 fresh water and provisions for a week, which might be taken as the limit of time 

 for such a boat to be absent from its base and dependent entirely upon its own re- 

 sources. If good weather or operation in sheltered water could always be counted 

 on, the complement of such a boat could be organized in a watch in two and be 

 thus reduced to a number for which it would be possible to provide living accom- 

 modations of an elementary character. Now let us assume that an effective radius 

 of 3,000 miles is required. Obviously, such a radius involves work in the open sea 

 with a possible period of independent operation of three weeks. Here a watch 

 in three is at once indicated with an increase in the number of the crew of about 

 50 per cent. Moreover, the living accommodations must be much more elabo- 



