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Lt. Rafael Castillo, left, Lt. Cristian Ahumada, and Lt. Patricio Puyol, of the Chilean submarine CS Thomson (SS 20), inspect the submarine rescue chamber as the chamber dives approximately 450 feet to Thomson during exercise CHILEMAR II. Photo by Petty Officer 3rd Class Spencer Mickler.  

by Capt. David M. Osen

At least 44 countries operate more than 400 submarines worldwide. The sophisticated safety measures in modern submarines and rigorous crew training reduce the risk of a serious mishap to an extremely low level, but nothing can reduce it to zero. Every submarine runs some small risk of a disabling casualty due to collision, flooding, equipment failure, etc.

If a disabled sub has an escape trunk and bottoms in less than 600 feet of water, the surviving crew can, at least theoretically, escape to the surface without outside rescue. But even at depths of less than 600 feet, it is preferable to rescue the surviving crew of a bottomed submarine if possible. All submariners are therefore interested in a robust rescue capability.

The United States fielded the world's first submarine rescue system in the early 1930s. The Submarine Rescue Chamber (SRC), essentially a diving bell with special hatches and a downhaul system for mating with a submarine, could rescue personnel from submarines in "shallow water" down to about 850 feet. The SRC proved its worth in 1939 by bringing up 33 survivors in four sorties to USS Squalus (SS 192), which had sunk off the New Hampshire coast. The Navy's current SRC differs little from the original one.

In 1963, USS Thresher (SSN 593) sank off New Hampshire in much deeper water with the loss of all hands. Although she passed crush depth long before reaching bottom, her loss highlighted the requirement for a deep-diving rescue system to close the gap between the shallow reach of the SRC and the depth at which a modern submarine could survive. For timely rescue in distant waters, the new system had to be transportable by air. The highly maneuverable Deep Submergence Rescue Vehicle (DSRV) developed to meet these requirements could be flown to a friendly seaport in the vicinity of an accident and loaded aboard a surface support ship or one of several nuclear submarines specially modified to serve as "mother submarines" (MOSUBs).

The DSRV's global reach opened up unprecedented opportunities for international cooperation. In an early step toward interoperability, Britain and France also modified some submarines to serve as DSRV MOSUBs. In 1986, the North Atlantic Treaty Organization (NATO) sponsored the first "Exercise Sorbet Royal," a multinational exercise focused on ensuring a practical capability to cooperate in all aspects of submarine rescue. The United States entered into agreements with other countries to provide rescue services in the event of a submarine accident. Under these agreements, the U.S. Navy began to conduct inspections to ensure that other navies' submarines were capable of DSRV and SRC rescue. The Navy also began to survey airports, roads and seaports to document the most efficient path for delivering a rescue vehicle and thus minimize the time-to-first-rescue (TTFR).

NATO established the Submarine Escape and Rescue Working Group (SMERWG) as a forum for working out issues such as making equipment interoperable and establishing common doctrine. Like the Sorbet Royal exercises, the SMERWG was open not just to NATO member nations, but to any country invited by NATO or a NATO member. In 2001, another grouping, the Asia-Pacific Submarine Conference (APSC), began to meet annually to discuss submarine operations in the Pacific and Indian Ocean regions. APSC discussions defaulted to submarine escape and rescue when few other topics could be identified that all participants would talk about.

The August 2000 loss of the Russian submarine Kursk provided fresh impetus for multinational coordination and collaboration in submarine rescue. In 2003, NATO established the International Submarine Escape and Rescue Liaison Office (ISMERLO) to operate under the SMERWG's authority as a clearing house for escape and rescue information, including facilitating rescue efforts. Hosted by Allied Submarine Command in Norfolk, Va., and staffed by experts from the U.S. and other NATO countries—as well as two billets for non-NATO nations—ISMERLO's main focus is a collaborative website where participating countries can share information about rescue capabilities and activities, discuss new initiatives, and quickly facilitate a multinational rescue in the event of a submarine sinking.

In 2008, the U.S. Navy replaced the aging DSRVs with the Submarine Rescue Diving and Recompression System (SRDRS). Whereas the DSRVs had had to wait for one of the few MOSUBs to reach the general vicinity of a submarine casualty, the SRDRS could operate from any vessel of opportunity (VOO), i.e., any naval auxiliary or commercial offshore support vessel with the deck space and strength to support the SRDRS equipment. Most regions of the world have ships that can serve as VOOs.

The SRDRS consists of three elements. The first is the Atmospheric Dive System 2000 (ADS 2000), a manned, one-atmosphere dive suit for inspecting a bottomed submarine and clearing escape hatches down to 2,000 feet. The second is the Pressurized Rescue Module (PRM)—named Falcon—a tethered, remotely operated rescue vehicle launched and piloted from the deck of a VOO. The PRM can rescue 16 sailors per trip down to 2,000 feet. The third element, scheduled to become operational in 2014, is a transfer-under-pressure (TUP) capability consisting of a deck transfer lock (DTL) that can mate with the PRM, receive Sailors exposed to high pressure, and transfer them to a decompression chamber without exposing them to normal atmospheric pressure.

The Navy team that keeps U.S. submarine rescue systems on call around the clock is the San Diego-based Deep Submergence Unit (DSU), which includes not only active-duty personnel, but also reservists, contractors and government civilians. In fact, more than half the DSU staff are reservists. The Submarine Escape and Rescue Review Group (SERRG), which supports the DSU, is chaired by Commodore, Submarine Development Squadron Five, and includes representatives from the DSU, the Atlantic and Pacific submarine commands, OPNAV, the Naval Sea Systems Command, ISMERLO, the Naval Submarine School and the Naval Medical Submarine Research Lab.

Like the DSRV before it, the SRDRS serves as the focal point for submarine rescue agreements with partner countries, which provide dedicated rescue ships or VOOs, transportation from qualified airports and seaports, or other support the participants deem appropriate. More than 20 such agreements are now in effect or under discussion. The goal is to load submarine rescue assets aboard aircraft at Naval Air Station North Island in San Diego, transport them to the location of a distressed submarine, and make them ready for rescue—all within 72 hours of notification.

The U.S. routinely participates in exercises designed to sharpen skills and accustom participants to working with personnel of other nationalities. The largest is the NATO-sponsored Exercise Bold Monarch, formerly called Sorbet Royal, which takes place every three years. In the words of NATO's invitation to prospective 2011 participants, Bold Monarch demonstrates "that NATO, in participation with submarine operating nations, can cooperate in lifesaving operations from a distressed submarine, including all medical aspects involved."

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Navy Diver 2nd Class Shane Olson goes through pre-diving inspections in the Atmospheric Diving Suit 2000 aboard the Military Sealift Command fleet ocean tug USNS Sioux (T-ATF 171) before a 500-foot dive. Photo by Petty Officer 3rd Class Spencer Mickler.

Ships, submarines and rescue systems from 14 nations took part in Bold Monarch 2008, while 26 countries sent observers. Submarines from the Netherlands, Norway, and Poland worked with rescue systems provided by three other countries. The U.S. rescue system was airlifted into the theater, providing considerable practice in the associated logistics. The U.S. PRM Falcon "rescued" over 200 personnel in 13 sorties to bottomed submarines. Most of the 29 flag-level dignitaries who visited the exercise got to experience being "rescued," including a French three-star rescued by a Russian system from a Norwegian sub.

The corresponding Pacific region exercise is called Pacific Reach, the regular participants being Australia, Japan, Singapore, South Korea and the United States. Singapore, which hosted the first Pacific Reach in 2000, also hosted the most recent one in August 2010. Thirteen countries sent observers in 2010, among them China, India, Indonesia, Malaysia, Pakistan, South Africa, Thailand, and Vietnam. Japanese, Singaporean, and Korean submarines worked with rescue systems from the U.S. and Singapore. The United States and Singapore also provided, respectively, the rescue and salvage ships USNS Safeguard (T-ARS 50) and MV Swift Rescue.

Many submarine-operating countries also conduct bilateral rescue exercises, one example being the U.S.-Chilean exercise called CHILEMAR. CHILEMAR was the brainchild of the commander of the DSU and the skipper of the Chilean submarine CS Simpson, who met while both were attending Chile's Naval War College. The first exercise took place in September 2008. In October 2010, CS Thomson participated in a second CHILEMAR off San Diego.

Time has always been the most critical factor in submarine rescue, and only a multinational effort can provide timely rescue in distant waters. It requires common technical standards, common doctrine, and close communication, as well as frequent multilateral and bilateral exercises, to build proficiency, mutual understanding, and trust. The SMERWG and the APSC provide the framework for common efforts. ISMERLO provides the communication medium and facilitators for rapid and effective collaboration. Bold Monarch, Pacific Reach and a host of smaller exercises provide the opportunities for honing cooperative rescue capabilities.

The U.S. Navy's small but highly professional submarine escape and rescue community, relying heavily on expertise from the reserve component, plays a central role in all of these activities, working with their counterparts around the world to provide prompt rescue for submariners trapped in the unforgiving depths.

Capt. Osen is the chief staff officer of the U.S. Navy's submarine rescue reserve component.