Mc Cann Rescue Chamber - History

History

During the first two decades of the United States Navy Submarine Force, there were several accidents in which Navy submarines sank with the loss of life. The impetus for the invention for the chamber was the loss of S-51 on 25 September 1925, and the loss of S-4 on 17 December 1927. In the case of S-4, all of her officers and men were able to reach non-flooded compartments as the submarine bottomed in 110 ft (34 m) of water. However, the majority soon succumbed. In her forward torpedo room, six men remained alive. Heroic efforts were made to rescue these six, who had exchanged a series of signals with divers by tapping on the hull. In extremely cold water and tangled wreckage, Navy divers worked to rescue them, but a storm forced a stop to this effort on 24 December. Forty men lost their lives.

These experiences led submariner Charles B. "Swede" Momsen to think of technical alternatives for rescuing survivors from sunken submarines, which at that time was still a virtual impossibility. Momsen soon conceived a submarine rescue chamber that could be lowered from the surface to mate with a submarine's escape hatch and proposed the concept through official channels. While in command of the submarine S-1 (SS-105), in 1926, Momsen wrote the Bureau of Construction and Repair (BuC&R) recommending the adoption of a diving bell for the purposes of rescuing entrapped personnel from submarines. But this idea was pigeonholed by the bureaucracy, even during his own subsequent assignment at BuC&R. The loss of S-4 with all hands put the Navy was very much "on the spot" because of the loss of lives that might have been saved. The pressure of this incident forced favorable action and Momsen, using the aircraft hangar from S-1, designed and built a prototype submarine rescue chamber.

During the first three months of 1928, divers and other salvage personnel were able to raise S-4 and tow her to the Boston Navy Yard, where she was drydocked and repaired. She returned to active duty in October 1928 and was employed thereafter as a submarine rescue and salvage test ship. Momsen went to sea in the reconditioned S-4 to carry out practical experiments and training with the rescue chambers.

Work with S-4 helped to develop equipment and techniques that bore fruit a decade later, when 33 men were brought up alive from the sunken submarine Squalus. The first diving bells for rescuing men from submarines were designed by the BuC&R in 1928. The diving bell went through a series of tests off the shores of Key West, Florida. Based on these tests, Momsen had several changes in mind for the bell, and after nearly two years of experimentation full of highly interesting results, the final bell was evolved and christened a "rescue chamber." This success was catalyst for gaining approval for development of the submarine rescue chamber in 1930. Before he could make these changes, Momsen went to the Bureau of Construction and Repair to work on an underwater breathing apparatus for individual escapes. Momsen turned to devising the "Momsen Lung", demonstrating it successfully in a series of unauthorized experiments in the Anacostia and Potomac Rivers, and finally attracted enough favorable attention to see the lung adopted by the Navy in 1929.

Lieutenant Commander Allan Rockwell McCann was put in charge of the revisions on the diving bell. From July 1929 to July 1931, McCann was assigned to the Maintenance Division, Bureau of Construction and Repair, where he developed the submarine rescue chamber. When the bell was completed in late 1930, it was produced as the McCann Submarine Rescue Chamber (SRC)(Navy designated the first 12 of these as 1-12, YRC-4 was lost aboard the USS Pigeon, at Bataan, Philippines during the first days of WWII. YRC-5 was aboard the USS Widgeon (AM-22) during the Pearl Harbor attack.). In 1931 a one-fifth scale model of a diving bell for submarine rescue work was built and tested. Design called for the bell to withstand the external pressure encountered at a depth of at least 300 ft (91 m) of water, and the test showed the model fulfilled this requirement with a factor of safety of about 3.5. The vessel was tested under external pressure, failure occurring in the shell at a pressure of 470 psi (3,200 kPa). Since the head of the vessel remained intact, it was decided to make a test of the head itself in order to determine its strength relative to that of the shell, and if possible to obtain some measure of the stresses occurring under load. The head collapsed at a pressure of 525 psi (3,620 kPa), indicating its strength under external pressure was about 10% in excess of that of the shell.

The revised Submarine Rescue Chamber had improvements including a soft seal gasket for sealing the submarine/bell interface skirting, and a floor installed to maintain air-space in the bell during raising and lowering. Momsen in his speech to the Harvard Engineering Society on 6 October 1939 credits Allan Rockwell McCann with the improvements which made the bell operational, safe and large enough to hold up to eight rescued crewmen and two operators.