What are emergency submarines?

Answer 1

Emergency submersibles are called DSRV's - Deep Submergence Rescue Vehicles. They are different from Bathyscaphe's in that they are specifically designed to dock and seal with a submarine's access hatch to rescue surviving crew members.

The most notable DSRV's are the U.S. Navy's Mystic (DSRV-1) and Avalon (DSRV-2). They have no specific homeport, and they are designed to be able to be transported by C-5 Galaxy aircraft anywhere in the world within 24 hours. The Mystic was used for filming part of the movie "Hunt for Red October". Though the underwater scenes are realistic, they're computer generated. The surfaced scenes showing her on the after deck of the USS Dallas (SSN-700) are authentic, though not necessarily the Dallas herself.

All hatches have 4 welded metal rings which are used by the DSRV to grab onto and then pull itself tight against the hatch surface (which is flat and kept well maintained). Once it has pulled itself against the hatch surface, the water is forced out and a sealing system keeps the water out at deep depths.

DSRV's have limited range, speed and propulsion, and as such they are carried to a site by a "mother" submarine - it docks itself over the after engineering access hatch for transport.

DSRV's are also used in recovery operations of lost aircraft, ships, weapons, etc., and other classified operations. It should be noted that though they are specifically designed for submarine crew rescue, their purpose is more psychological, and one of search and recovery than search and rescue. Most submarines operate in water depths far exceeding their design limits should they ever sink, and a DSRV rescue, while feasible, can only occur if the boat in question is not on the bottom of the ocean at an angle preventing it from docking to the access hatch. Depths at which the ocean is beyond the design limits of submarines isn't very far from the shorelines of most countries - only about 100-200 miles (past the edge of the Continental Shelf). All submariners, myself included, always know that in the event of a major casualty, rescue is pretty much hopeless. If the casualty is significant enough to sink the boat, it'll likely result in the loss of all hands as well, and even if there are survivors, the boat must be located first. This was the case with the Russian submarine Kursk - several survivors died after the accident because it took time to locate the wreck.

The notable exception is if a boat is struck by a surface vessel while transiting to and from homeport and isn't submergedt. Since submergence typically doesn't occur until the boat reaches deeper water, if struck and sunk it would likely be in shallower water and rescue would be feasible. However, submarines have a huge pscyhological effect on surface ships as well, and most tend to give surfaced boats a wide berth (don't irritate the guy who can sink you with the push of a button).