Captain Dudley W. Knox to Rear Admiral Ralph Earle, Chief of the Bureau of Ordnance
U. S.NAVAL FORCES OPERATIGN IN [EUROPEAN] WATERS
Telephone. Victoria 2110 30, Grosvenor Gardens
Cable Address”Simsadus” London, S.W. 1.
1 February, 1918.
My dear Ralph:-
As you know, Captain Leigh is over here in charge of anti-submarine development and operations for our navy.
Recent experiments indicate that a “C” tube mounted on a submarine will give a directional indication of another submarine within one degree if used by an expert listener. In the hands of even a greenhorn its error will probably not exceed five degrees.
It has been proposed to mount two “C” tubes on a submarine, one in the horizontal plane and one in the vertical plane, and ascertain if it is not possible to bring this submarine into close contact with another submarine, regardless of whether the latter is submerged or not.
Leigh has agreed to take the matter up with Bureau of S.E. and have such experiments conducted in America, where it is thought they may be pushed to an earlier completion than if undertaken over here.
I have agreed to write you with respect to the development of a proper weapon for use under the assumption that the experiments will demonstrate the efficiency of the sound devices.
It will be readily comprehended that the normal situation resulting from approaching an enemy submarine by means of listening devices will be:-
Your own sub will arrive at close quarters with his bow pointing towards the enemy, and with the axis of our boat also pointing directly towards the enemy in both the vertical and horizontal plane. Probable we would get a stern or quarter presentation of the target, which would not give a good danger space
for <but by> maneuvering so as to approach the enemy from a higher or lower level than himself, or possibly on a course which intercepts him at an angle that is not too acute, a better presentation of the target may be attained. This question of maneuvering however is so problematical that it must not be counted upon in our preliminary plans.
What can you do to give us a suitable weapon for use under the<se> peculiar circumstances?
I omitted to mention among the assumed conditions that the sounding devices will give an approximate range-- say it will be estimated with sufficient accuracy to know when you are inside of 500 yards and outside of 100 yards, and also when you are inside of 150 yards.
The first thing suggested is the ram: but ramming while submerged does not appear desirable if it can be avoided; unless some special extension to the hull can be made. The extension idea suggests the old spar torpedo.
It seems to me that the shot-gun torpedo idea would come in here very advantageously. But unless they can be developed quickly, and without involving material modification of the present tube installation, it would be too late to make them count much in the present situation.
With a flock of four or five torpedoes from each of two or four tubes I think the chances of at least one hit inside of five hundred yards should be excellent.
If the listening device experiment pans out the need for a proper weapon will be immediate and urgent. Can you not concentrate the brains and energy of your very brainy and energetic Bureau upon this question?
Do you mind letting G.L. Smith, or whoever is now handling Schofield’s old job, see this letter and seek his assistance. Of course you can keep in touch with the sound device proposition through S.E.
By the way the value of air craft in anti-sub work is to my mind extremely doubtful. They fly on an average of 5,000 miles before getting in touch, and even then cannot do much against them.
With many kind regards,