The British SEIE Mk 10 (left).

Exercise Sorbet Royal

A NATO exercise, Sorbet Royal in May 2002 (Cohen 2003), demonstrated the effectiveness of the system when four crewmembers and five others from Denmark, the UK and USA, both men and women, donned SEIE suits to simulate an escape from the Swedish submarine Vastergotland, down 115 feet off the coast of Denmark. The submarine’s escape tower had a four to six minutes recycle time, (determined chiefly the time it takes to drain the flooded tower) but they used a 15-minute interval for this demonstration. The exercise worked as briefed, with 18 seconds required for the pressure equalisation phase, the pressure doubling roughly every four seconds or so, and nine seconds required for the ascent. Rescue units, including a decompression chamber, were waiting in smooth seas on the surface.

Russian experience

Improperly conducted escapes can lead to the bends which, without immediate recompression, are generally fatal. Another real life factor is hypothermia. When the Soviet submarine Komsomlets sank in the Norwegian Sea in 1989, 34 of 69 crewmen escaped but died of hypothermia, heart failure or drowning (Polmar 2000).

The Kursk had escape-survival suits rated to 328 feet (100 metres). Like most other Russian submarines, it also had a built-in escape pod in the sail structure, big enough for the entire crew, but this was probably destroyed by the initial explosions. The Komsomlets also had a pod, which broke free as the boat plunged to the bottom at 5,500 feet (1,676 metres). Tragically, toxic gas entered the pod and only one of its five occupants survived.

Water depth may preclude a buoyant SEIE ascent, therefore the survivors must wait for rescue. Rescue is always preferable to escape but rescue systems are expensive.

Following the loss of USS Thresher in 1963, the USN developed two extremely capable 24-man Deep Submergence Rescue Vehicles (DSRVs). The 30-ton DSRV can be flown to a convenient embarkation port from where it can be piggy-backed on a specially modified nuclear submarine or rescue vessel to the accident site.

The DSRV rescues survivors under pressure, theoretically down to 5,000 feet (1,500 metres), well beyond the collapse depth of any existing submarine. However it cannot transfer them under pressure without a special vessel fitted with decompression facilities. The USN has eight submarines, the British four and the French two that can operate the DSRV (Walsh 2000) but only the four British ballistic missile nuclear submarines have the additional recompression chamber (RAN 2000).

The USN also possesses two McCann “diving bell” rescue chambers, rated to 1,200 feet (366 metres). Developed in the 1930s, one featured in the successful USS Squalus rescue in September 1939. Unfortunately, the McCann Bell suffers from severe operational limitations in that a diver must attach a haul-down cable.

Several nations have rescue submersibles, such as the British LR5. However, they are launched from surface ships, so they too are limited by weather and ice conditions. Some are also limited by depth, such as the British LR5’s 1,312 feet (400 metres).

 

A British LR5 launching in flat calm seas.

After the Remora failure on 4 December 2006, when its main lift cable parted off Rottnest Island in heavy seas, the RAN has relied on the LR5. This “manned submersible” weighs 21.5 tons and operates to a maximum depth of 400 metres with its crew of three in wave heights of five metres. Its maximum speed is 2.5 knots and the LR5 requires a Vmax of one knot of bottom current to mate successfully with the submerged submarine.The LR5 requires a heel of less than 10 degrees and a 60 degrees bow up attitude on the distressed submarine, but this may be modified with 15 degree wedges. Its chamber will accommodate 15 survivors at a time. Australian support vessels have been modified to accept the vehicle and it employs the standard NATO rescue seat, with which our submarines are fitted.

The LR5 is air-transportable. For the annual Black Carillon submarine escape exercise programmed for late 2009, two standard containers of auxilliary equipment were transported by commercial airline and the submersible itself was carried by an RAAF C-17. (Navy News photo: LAC Benjamin Evans, 11 June 2009.)

RAN experience

In the early 1990s the RAN’s six Oberon class submarines were being replaced by the Collins class. The RAN, following UK procedures, built a modern submarine escape training facility at HMAS Stirling in Western Australia. This included two air-portable recompression chambers nominally capable of treating six patients, and stocks of equipment to deploy to the site of a submarine accident.

However, the waters off Sydney, in which the Oberons generally operated, have a very narrow continental shelf. Therefore escape systems were generally regarded as existing chiefly for morale purposes. If a submarine sank more than a few miles off the coast it would fall quickly beyond its safe hull depth or to depths beyond which escape was impossible. In either event a quick death for the crew would be the likely outcome.

RAN submersible, 1987

The RAN required some sort of rescue system compatibility and as far back as the mid-1980s fitted a rescue flange on the casings around the Oberons’ forward escape towers. In 1987 the RAN acquired a small submersible and support ship but found the cost of refurbishing was prohibitive, so this was abandoned in 1992.

Next, the RAN commissioned a study that resulted in the 1994 formation of project group tasked to acquire:

• recompression facilities for nine stretcher-borne and eight to ten seated patients;
• a means of transferring emergency stores into a sunken submarine;
• a means of transferring the seated patients under pressure to alternative re-compression facilities;
• a submerged rescue capability, probably through a leased service from a foreign navy; and
• significant improvements in the Australian submarine escape and rescue infrastructure.

Skills training

Analysis indicated only two viable rescue system options existed. Either the RAN could lease the Royal Navy’s submersible LR5 on a “stand-by fly-away” basis or it could build its own. The American DSRV, although highly capable, was impractical because it lacked support assets in Australia.

With the exception of the McCann Bell, all rescue systems used free-swimming submersibles. The skills to operate the systems are found in the offshore diving/oil industry or developed and maintained in-house by naval personnel. The USN employed 120 contractors and 210 naval personnel on a full-time basis.

In either case, skills maintenance required deployment of the rescue vehicles, every four to six weeks, at significant ship and personnel costs. Even when commercial resources were used, such as by the RN with a team of eight, industry could not be relied upon as a source of skilled operators. All mechanical sub-surface operations were carried out by saturation divers or remotely operated vehicles (ROVs).

The submersibles are also complex, heavy and expensive to maintain. Additionally, they require specialised support vessels, few of which operate near Australia.

Chartering the LR5 initially looked viable, but further analysis revealed problems. Although the standby costs for LR5 were insignificant, the only way to guarantee a support vessel (without purchasing one) would involve constant charter for an indeterminate period. Such a charter would use up several million dollars in only a few months. These costs would be overwhelming and would not guarantee vessel availability if it was needed for an Australian emergency response.