Submarine Rescue Diving and Recompression System (SRDRS)

The Navy's Deep Submergence Rescue Vehicle (DSRV) and Submarine Rescue Chamber (SRC) provide the service's current capabilities for submarine rescue. These systems are designed for quick deployment in the event of a submarine accident. They are transportable by truck, aircraft, ship, and, for the DSRV, by specially configured "mother" submarines. The DSRV is expensive to maintain, requires dedicated aircraft for transportation, takes at least 24 hours to arrive at a nearby port, and must be carried by ship or submarine to the disabled submarine.

The Deep Submergence Rescue Vehicle (DSRV) was the principal asset for submarine rescue in the US Navy. This vehicle is designed to transport personnel rescued from a disabled submarine (DISSUB) to the safety of an awaiting Mother Submarine (MOSUB). The DSRV-MOSUB system was phased out of the Navy inventory during the early years of the 21st Centery and replaced with the Submarine Rescue and Diving Recompression System (SRDRS). The Submarine Rescue Diving and Recompression System (SRDRS) will be the Navy's 21st century submarine rescue system.

The Submarine Rescue Diving and Recompression System (SRDRS) offers several advantages over previous Navy rescue systems: a rapid response time, elimination of the need for a mother submarine or dedicated surface support ship, and newer technology. SRDRS will fill the gap created by the decommissioning of USS PIGEON (ASR 21) and USS ORTOLAN (ASR 22). While the DSRV can rescue survivors under pressure, it cannot transfer them under pressure without a specially designed mother ship with inbuilt decompression complex. The two ships with such capability have now been scrapped and the only means of transferring under pressure is to use a British ballistic missile nuclear submarine which has a modified forward compartment capable of use as a decompression chamber.

SRDRS will provide a new capability of pressurized transportation of rescuees from a stricken submarine directly to the decompression system eliminating the requirement for Deep Submergence Rescue Vehicles, Mother Submarines and Submarine Rescue Chambers. SRDRS is to include an air transportable rapid assessment/underwater work system, a decompression chamber system and a pressurized rescue module. The SRDRS will provide a global rapid response capability to support submarine rescue missions with an increase in capability at a fraction of the cost of the currently available systems.

The Submarine Rescue Diving and Recompression System (SRDRS) consists of four distinct elements, which include the Assessment/Underwater Work System (AUWS); Submarine Decompression System (SDS); and the Pressurized Rescue Module System (PRMS); and PRMS Mission Support Equipment, including the Launch and Recovery System (LARS) a deck mounted A-frame crane used to launch and recover the PRM. The SDS, PRM, LARS, and associated generators and auxiliaries all compose the Submarine Rescue System (SRS). The Submarine Rescue Diving and Recompression System (SRDRS) consists of the Submarine Rescue System (SRS) in conjunction with the Assessment/Underwater Work System (AUWS). These systems are designed to rapidly deploy to any location in the world via air and ground transportation and will be installed on a military or commercial vessel of opportunity (VoO). The SRS, approximately 183 tons, is installed aboard the VOO.

The Assessment/Underwater Work System (AUWS) consists of 2,000-foot atmospheric diving suits with launch and recovery systems (LARS), a flyaway sonar, remotely operated vehicles, and associated support equipment. This is the first system mobilized in the event that a submarine becomes disabled. The system will help locate and mark the disabled submarine, assess surrounding conditions, and clear debris from a submarine's hatch. The ADS2000 (or HARDSUITtm 2000) Atmospheric Diving System (ADS) is first component of the manned rapid Assessment Underwater Work System (AUWS) segment of the US Navy's future Submarine Rescue Diving and Recompression System (SRDRS). The ADS2000 provides a rapid response capability for DISSUB localization and assessment, hatch clearance, and emergency life support stores (ELSS) replenishment. The dually redundant ADS 2000 system consists of two ADS2000 atmospheric diving suits depth rated to 610 m, two Launch & Recovery main skid assemblies, and one control van, spares van, and miscellaneous mission support equipment and spare parts. The ADS2000 interior remains at one atmosphere, allowing the pilot to operate at depths to 2000fsw for extended periods and return directly to the surface, without the attendant costs and risks associated with decompression. The ADS2000 is easily deployed to survey and establish contact with the DISSUB, and commence stabilization of the DISSUB condition through use of the Emergency Life Support Stores (ELSS) Pod system and/or the Decompression - Ventilation System.

The Submarine Decompression System (SDS) consists of two large submarine decompression chambers and support equipment. The Deck Recompression System (DRS) consists of a Hyperbaric Transfer Chamber (HTC), a Deck Transfer Lock (DTL), and two 36-man capacity Surface Decompression Chambers (SDCs) into which rescued personnel can be transferred under pressure and safely decompressed to atmospheric pressure aboard the rescuing surface ship. This system will be located on the VoO and provide controlled decompression for personnel that have escaped or been rescued from the disabled submarine.

The Pressurized Rescue Module System (PRMS) is needed to recover and rescue personnel from a disabled submarine. The PRMS consists of the pressurized rescue module, transfer skirt, control van, umbilical winch, launch and recovery system, deck cradle, and support equipment. The pressurized rescue module (PRM) is a tethered, remotely operated submarine rescue vehicle. It consists of a horizontal cylinder hull with hemispherical ends situated inside an open frame. Navigation, video, propulsion, and life support systems are mounted externally on its frame and hull. The vehicle is designed for submerged transit to a depth of 2,000 feet of sea water, for docking and mating to a disabled submarine up to a 45-degree response angle, for evacuation capabilities for disabled personnel, to provide a hyperbaric habitat, and to transfer personnel to the SDS. The Pressurized Rescue Module (PRM) is capable of transporting up to 16 rescued personnel under pressures up to 5 ATA from the DISSUB to a surface ship. The PRM has a dedicated Horizontal Manway capable of mating with the Deck Transfer Lock (DTL) to permit the direct Transfer Under Pressure (TUP) of rescuees and attendants into the SDS decompression chambers on deck.

The Submarine Rescue Diving and Recompression System utilizes a tethered, remotely operated Pressurized Rescue Module (PRM) deployed and controlled from a Vessel of Opportunity (VOO). The PRM is launched and recovered using a deck mounted A-frame crane called the Launch and Recovery System (LARS). Once the SRDRS is installed on a VoO and transited to the site of the disabled submarine, the PRM is launched into the ocean via a stern mounted A-frame designated as the LARS. The LARS utilizes a cursor frame and dual heave compensated recovery winches for lifting and handling the PRM.

Once submerged, the PRM is remotely monitored and operated from a control van located on the VoO. The control van is essentially the command and control station for the PRM and consists of controls for piloting, providing power distribution, and monitoring life support systems. The control signals are sent to the PRM via an armored cable, or umbilical, which has its payout length regulated from the umbilical winch. The PRM will be remotely piloted to the disabled submarine where it will mate to the deck of the submarine over its hatch. Mating occurs via an articulated mating skirt called the transfer skirt. This subsystem allows the PRM to mate up to disabled sub angles of 45 degrees, while the PRM maintains a horizontal position. The transfer skirt is large enough so that mating, hatch opening, and personnel transfer can be achieved without removal of any disabled sub hatch fairing. Once the PRM is mated with the submarine, two onboard attendants will assist with the transfer of submariners into the PRM. The attendants also control and monitor life support functions.

Once the transfer of rescued submariners is complete, the PRM will detach from the submarine and ascend to the submerged cursor frame suspended from the LARS. The PRM is then recovered from the sea and landed on a deck cradle installed onboard the VoO. Upon recovery, the PRM docks with the Submarine Decompression System (SDS) to allow transfer and decompression of personnel. The attendants and those rescued are then transferred under pressure to the SDS from the PRM via a pressurized flexible manway.

The SRDRS concept of operations has been developed to support rescue of up to 155 personnel from a pressurized DISSUB. The PRM accommodates 16 rescuees per trip and requires two Operators. Each SDC can accommodate up to 36 persons (32 rescued personnel and four Tenders). Two PRM trips, or sorties, to and from the DISSUB will therefore be required to fill each SDC before decompression of its occupants can commence. At least 10 sorties will be required to rescue a 155-man DISSUB crew. It is anticipated that each PRM Operator/SDC Tender will be a Second Class Diver qualified as an inside chamber tender/Diving Medical Technician (DMT).

PRM operators/SDC tenders would be allowed to participate in a repetitive sortie only after completion of a 24 hr surface interval following emergence from the SDC. As a result, a minimum of 20 PRM operators/SDC tenders will be required to complete the minimum 10 PRM sorties necessary to rescue a 155-man DISSUB crew. On the other hand, opportunities for potential repetitive sorties by Operators/Tenders can be contemplated that would reduce minimum PRM/SDC Operator/Tender manpower requirements. Oxygen-accelerated decompression as part of a repeated-dive profile could permit 10 operators to rescue a fully-manned submarine. Even emergency-use decompression schedules must keep the overall incidence of DCS within acceptable limits without imposing unacceptably severe symptoms or signs of pulmonary or CNS oxygen toxicity.

One of the gaps in legacy program was the ability for personnel to Transfer Under Pressure, which would allow rescue of crew members at deep depths under immense pressures and transfer them to a decompression chamber. The acquisition of the Submarine Rescue Diving and Recompression System would fill this gap while also providing a significantly more capable, state-of-the-art system. This will include a dramatically improved deep-diving capability, a pressurized rescue system, and a decompression system.

If adequate Transfer Under Pressure or recompression assets are not available after rescue from a pressurized Disabled Submarine the rescuees may stiffer from severe or fatal decompression illness (DCI). The Deep Submergence Rescue Vehicle (DSRV) submersible mates with the disabled submarine and transfers surviving crewmembers to the surface or another submarine. The DSRV can be pressurized internally if the submarine itself is under pressure, but as there were no surface chambers that allow transfer under pressure, rescued personnel must be decompressed to sea level and recompressed in a surface-based chamber for subsequent saturation decompression. The initial decompression to sea level may result in a high incidence of DCS. A transfer under pressure chamber allows working divers to be moved between a worksite and living chambers (also called deck compression chambers) without disturbing off-duty divers. Transfer Under Pressure (TUP) to and from pressurized environments such as submarines or hyperbaric chambers is essential where being subjected to ambient pressure may be life threatening.

The SRS was nominally designed for operation on the US Navy's Auxiliary Fleet Tug, T-ATF, but is actually intended to be a fly-away system, capable of being installed on any available VOO near the disabled submarine. The VOO may be any Offshore Supply Vessel (OSV), Anchor Handling Tug, or offshore barge that has the capacity to handle the SRS and is available in the area of a disabled submarine. Since the SRS must be rapidly deployed, potential VOOs must be quickly identified and evaluated for structural, stability and seakeeping suitability with respect to the requirements for the SRS.

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