Submarine Rescue Chamber (SRC) / McCann Bell

The US Navy possessed a number of McCann submarine rescue chambers. These diving bells were developed in the 1930s and one featured in the only successful submarine rescue ever undertaken; that of USS Squalus in September 1939. The McCann bell suffers severe limitations in strong currents and when dealing with a pressurised submarine or one lying at extreme angles. The USN SRC is air transportable to a VOO MOSHIP which requires little modification to use the system. Transfer Under Pressure (TUP) to and from pressurized environments such as submarines or hyperbaric chambers is not possible with this system, even though TUP is essential where being subjected to ambient pressure may be life threatening.

As of 2000 there were two Submarine Rescue Chambers (SRC) that can be rapidly transport to a support vessel to be used at the location of a disabled submarine. If a US Navy auxiliary vessel cannot respond to the scene fast enough, any one of the world's estimated 4,000 commercial supply/handling vessels can be used if made available. The SRCs, capable of rescue down to 850 feet, can be mated to a disabled submarine by using a down-haul cable attached to a special pad-eye on all US submarine hatches. Underwater exploration has fascinated people for thousands of years, yet submarine travel did not become common until the mid-twentieth century. The earliest description of how a diver might be supplied with air beneath the waves is found in the writings of Aristotle, who described what is essentially a diving bell. By submerging inside a weighted object shaped roughly like an upside-down bucket, the diver can breathe the air trapped inside. The ancient Athenians used divers in secret military operations, and a legend maintains that Alexander the Great descended into the sea in a primitive diving bell.

Charles Bowers "Swede" Momsen entered the US Naval Academy in 1914. After a brief tour in battleships, he entered the Submarine School in 1921 and achieved his first command in 1923 with the USS O-15 (SS-76). Later, as Commanding Officer of USS S-1 (SS-105), he found the wreck of the USS S-51 (SS-162), lost with 33 men in a collision with the steamer City of Rome east of Long Island Sound in 1925. That harrowing experience led him to ponder technical alternatives for rescuing survivors from bottomed submarines, which at that time was still a virtual impossibility.

Momsen soon conceived the idea of a submarine rescue chamber 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 to the Bureau of Construction and Repair and recommended the adoption of a diving bell for the purposes of rescuing entrapped personnel from submarines. But this was ignored by the bureaucracy, even during his own subsequent assignment at the Bureau of Construction and Repair.

On 17 December 1927, while conducting submerged trials off Provincetown, Massachusetts, the American submarine S-4 was rammed by the U.S. Coast Guard destroyer Paulding (CG-17). Holed in the starboard side, just forward of her deck gun, the submarine sank immediately. All of her officers and men were able to reach unflooded compartments as S-4 went to the bottom in 110 feet of water. However, the majority, who had gone aft, soon succumbed. In her torpedo room, forward, six men remained alive. In extremely cold water and tangled wreckage, Navy divers worked desperately to rescue them, but a storm forced the abandonment of this effort on 24 December. In all, forty men lost their lives in the tragedy.

The S-4 was lost with all hands and 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 on the diving bell project. During the first three months of 1928, divers and other salvage personnel were able to raise the sunken 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 her 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 Bureau of Construction and Repair, Navy Department, 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 then the 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 escapesteach. 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 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 introduced as the McCann Rescue Chamber. 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 feet of water, and the test showed that 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 lbs. per sq. in. 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 lbs. per sq. in., indicating that its strength under external pressure was about 10% in excess of that of the shell.

The rescue chamber was a pear shaped steel chamber, the big end uppermost, seven feet at the greatest diameter and ten feet high. It is divided into an upper closed compartment and a lower open compartment by a horizontal bulkhead which has a water tight hatch in its middle. Surrounding the lower compartment is a ballast tank of a capacity just equal to that of the lower compartment. Inside the lower compartment is a reel with 400 feet of " steel wire on it. The reel is operated by a shaft leading into the upper compartment. The shaft is rotated by an air motor. On the bottom edge of the lower compartment a rubber gasket is embedded into a circular groove, so that when the chamber is brought into contact with a flat surface (the hatch ring) a water tight joint may be effected with the application of pressure. Attached to the upper compartment is an air supply and an atmospheric exhaust hose, wire wound for strength. Also electric cables for telephone and light are attached. A wire pendant for hoisting and lowering is shackled into a padeye on top. This wire is also used for retrieving the chamber in case of emergency.

A new submarine, SS-192 Squalus (Lieutenant Oliver F. Naquin) submerged with the main engine air induction valve open and flooded the aft compartments on the morning of 23 May 1939 off Portsmouth, New Hampshire. Submarine rescue ship USS Falcon (ASR-2), commanded by Lieutenant Grant A. Sharp, was on site within twenty-four hours. At the time of the Squalus disaster, Momsen was serving as head of the Experimental Diving Unit at the Washington Navy Yard. The forward and after hatches of American submarines were fitted for attaching the rescue chamber. They have a flat doughnut shaped plate welded to the hatch combing upon which the bottom of the chamber rests and a bail over the center of the hatch to which the haul down wire must be attached by the diver.

Although 26 men lost their lives in the initial flooding, at 1130 on 24 May, USS Falcon (ASR-2) lowered the newly developed McCann rescue chamber -- a revised version of a diving bell invented by Commander Charles B. Momsen -- and, in four trips over the next 13 hours, all 33 survivors were rescued from the stricken submarine in the first deep submarine rescue ever. Along with Momsen, McCann received a commendation from President Franklin D. Roosevelt for his efforts in the rescue.

Although there was no reason to believe anyone was alive in the aft part of the ship, a fifth run was made to the aft torpedo room hatch on May 25. This run confirmed the flooding of the entire aft portion of the ship. Then in the following three months, the Squalus herself was brought to the surface in an even more challenging salvage operation. Although, the cause of her loss was never full determined, the submarine was later refurbished and, as the Sailfish, distinguished herself in World War Two.

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