When the radar existed only in science fiction but the aviation was already here, the most common way of spotting a distant target was to send a reconnaissance aircraft based aboard a battleship or a cruiser.
For submarine fleet, spotting and early warning was probably even more vital than for the large surface ships. No wonder that during and soon after WWI, several countries including the USA, United Kingdom, Germany, Italy, Japan and the Netherlands looked into the possibility of submarine aircraft carriers.
The US Navy commissioned Glenn L. Martin to design and construct a naval scout airplane designed to fold and be carried inside sealed tanks on the decks of submarines. Glenn L. Martin design, the MS-1, first flew from Lake Eyrie early in 1923 and later the same year conducted trials on board the USS S-1 from Hampton Roads, Virginia.
As it turned out the USS S-1 was the only submarine converted with an aircraft hangar, built aft of her conning tower. Fully loaded the MS-1, 5.08m long with a wingspan of 5.34m, weighed only 1000 pounds. It carried no armament as it was designed purely as a spotter aircraft.
The MS-1 had to be reconstructed on the deck of the submarine before every flight and dismantled when placed into storage. The procedure for launching and recovering the MS-1 involved the partial submerging of the submarine. Six MS-1's were built in total before the programme was canceled.
The other experimental scout airplane, tested on the same S-1 sub, was the all-metal Cox-Klemin XS. It was slightly larger than the MS-1. Five XS-1 aircraft were powered by a 60hp Lawrence engine, and the XS-2 (one built, shown above and below) had more powerful 84hp Kenner engine.