The U.S. Navy is in the process of updating its submarine rescue capability with procurement of the Submarine Rescue Diving and Recompression System (SRDRS). Despite its atrocious title, the system gives promise of an effective and highly mobile means of rescuing survivors from submarines disabled in relatively shallow water, i.e., down to current U.S. submarine collapse depth of some 2,000 feet.
The SRDRS will replace the Navy's two long-serving deep submergence rescue vehicles, the Mystic (DSRV-1) and the Avalon (DSRV-2). The Avalon was laid up in fiscal year 2001 and will be kept in lay-up until 2005 for emergency requirements; the Mystic, having recently completed an extensive overhaul, will be kept in service until at least 2003, when the SRDRS is delivered.
A tethered, remotely operated vehicle (ROV)—based on the Australian Navy's Remora—is the primary component of the new rescue system. The ROV will dive to the stricken submarine and maneuver into position to mate with her forward or after escape batch. An articulated "skirt" beneath the vehicle will permit it to mate with a disabled submarine lying at a significant angle; 45 deg. to the horizontal will be the minimum angle, 60 deg. the goal. The ROV will be self-sufficient with regard to electrical power and air, with the tether to guide it back up to the surface ship. As it reaches the surface, the vehicle will be lifted out of the water and onto the decompression chambers by a specially built launch and recovery system.
The ROV's operation will be controlled from the surface ship, with the operator having comprehensive displays of the in situ environment based on sonar as well as television cameras on the ROV. The vehicle will carry two crewmen, to provide on-scene evaluation of the situation and to help survivors enter. The threshold for the number of survivors that can be accommodated is 12, with a goal of 15.
The surface ship component of the SRDRS will be a ship of opportunity carrying the extensive support/control/decompression facility. The system is designed to fit on board a variety of merchant and naval ships, with minimum demands on the ship for services. The SRDRS will have its own control room, maintenance shop, winch, air, power, deep-sea mooring gear, and other components. All components—including the ROV—will be sized to fit in a standard container footprint, i.e., 8 x 8 x 40 feet.
A most important component of the shipboard SRDRS will be two decompression chambers, each able to treat 31 survivors, bringing them up from a six-atmosphere environment. Such situations occur in a stricken submarine as water leaks into the pressure hull, compressing the remaining air, or when air is introduced into the hull to stop incoming water. Without proper decompression the survivors would suffer bends, an often crippling or fatal disease.
In the SRDRS system, when the ROV carrying survivors is brought on board ship it can mate with a module fitted between the two decompression chambers, enabling survivors, under pressure, to move directly into either chamber. Obviously, one of the shortfalls of the system is being able to decompress a maximum of some 77 survivors at any given time—31 men in each of the two chambers plus perhaps 15 in the ROV itself.
The Navy is developing accelerated decompression tables for use with the new system.
(With the DSRV, more survivors could have been decompressed by using the entire forward compartment of the mother submarine, which could be pressurized to one atmosphere. The now-discarded submarine rescue ships [ARSs] had decompression chambers to which the DSRVs could mate.)
In an effort to ensure that the SRDRS can reach a disabled submarine anywhere in the world within a goal of 72 hours, the Navy is identifying several hundred ships of opportunity that could accommodate the system. Probably based at Naval Air Station North Island, home of the DSRVs, the SRDRS would be flown to a port near the downed submarine, trucked to pierside, and loaded on board ship. Several sets of steel SRDRS templates will be prepositioned around the world. In the event of a submarine disaster with survivors, the ship of opportunity would be identified and a set of templates flown to a port and placed on board the ship. Laid out on her deck, these will mark the locations for all SRDRS components. Thus, as the containers arrive on the pier, they can be hoisted on board and bolted or lashed in the proper positions with minimum loss of time.
Use of ships of opportunity is a major advantage over the DSRV system, which can be operated from only a few mother submarines—eight U.S., four British, and one French undersea craft. However, being submarine-supported provided an all-weather and under-ice capability not possible with surface ships. The SRDRS system is planned to be useable from surface ships in at least sea state 4 with a goal of sea state 5.
Under current planning, the Navy will procure one SRDRS system with two ROVs to ensure that one vehicle is always available when the second is undergoing maintenance.
The U.S. Navy submarine community believes the fleet will have a viable and affordable rescue capability with the availability of the SRDRS in 2003. The SRDRS may be supplemented by two McCann-type submarine rescue chambers. The McCann chamber was developed in the 1930s and was used to pull 33 survivors from the sunken submarine Squalus (SS-192) in 1939. This was the U.S. Navy's only submarine rescue operation using a rescue vehicle. The submarine rescue chambers, which require diver support, are capable of functioning to a depth of 850 feet.
Also, the Navy is procuring the British-developed submarine escape and immersion equipment to provide enhanced escape capabilities to U.S. submariners. These full-body suits include thermal protection and have a built-in life raft. They provide a realistic capability for escape from depths to 600 feet and for survival on the surface. Heretofore, the possibility of successful escape from such a depth by submarine crewmen as well as their survival on the surface (without immediate support) were speculative at best.
Thus a combination of the Submarine Rescue Diving and Recompression System, submarine rescue chamber, and submarine escape and immersion equipment is expected to provide the best possible features that are affordable and effective for saving survivors of disabled submarines.