Earlier this year the record of the Indonesian submarine KRI Nanggala-402 was located resting on the seabed off the coast of Bali. The whole crew of 53 submariners were declared dead on board. Due to the considerable time taken to locate the sunken vessel, the oxygen supply what's totally depleted. In many ways this showed that there is a need for an improved methodology for submarines to be able to rescue themselves when serious accidents occur underwater.
On April 21st the submarine took part in a torpedo firing exercise. No one is quite sure what happened but the end result was that the kRI Nanggala-402 suffered a catastrophic loss of power and sank to the seabed. The next day the media were informed by the Chief Staff of the Indonesian Navy, Yudo Margono, that the submarine possessed oxygen reserves which should last for at least 3 days. That meant the clock was ticking down for the crew and the oxygen would run out on the 24th of April. In spite of there being 9 Indonesian warships, along with help from the Malaysian, Singaporean, Indian, and Australian navies, plus a US Navy P-8A Poseidon Patrol aircraft, the submarine was only found on the 24th day itself, leaving the possibility of any survivors doubtful.
Historically speaking, the deepest unassisted escape from a submarine was by British Submariner called Bill Morrison. In 1945, towards the end of the Second World War, the submarine XE11 he was on was sunk in Loch Striven in Scotland. In spite of coming to rest more than 200 feet below the surface, the submariner managed to escape through the escape hatch. Coming up so quickly from such depths caused the bends and Morrison surfaced unconscious, with severe bleeding from his nose, ears and mouth. He would continue to have serious pains in his whole body for the rest of his life.
The escape systems on a modern submarine are effective down to the maximum depth of around 600 ft. To put this in perspective, if you were wearing scuba gear and had an Open Water Certification, then you would be able to dive now to 60 ft. An advanced diver can go to a depth of 130 feet. Professional divers, breathing a mixture of hydrogen, oxygen and helium, can operate at a maximum depth of around 200 ft. Breathing this helium mix avoids the “bends”, which are also known as “nitrogen narcosis.” They also have to surface very slowly indeed and to do so, make use of a decompression chamber.
Present-day US Navy submarines make use of a special airlock which are called “escape trunks.” During an emergency, each can release up to two survivors per cycle. These submariners will enter the trunk wearing special escape suits and then lower a hatch behind them. These escape suits are then pressurized for rapid buoyancy. The trunk itself is filled with water and the submariners are released rapidly in order to minimise the high-pressure exposure at depth. They ascend rapidly but are cocooned within their high pressure suits. During this process they are able to breathe normally. Once they reach the surface, the escape suit which is known as a “Submarine Escape Immersion Equipment”, becomes a life-raft in order to protect the submariners from the effects of hypothermia.
The problem is that at great depths the pressure is so extreme. In an effort to reach an equilibrium, the submariner may struggle to survive. But in 1987, 25 driving instructors made an escape from a depth of 603 ft. One of them, an instructor called David Wadding, later gave an interview in which he said, “I can assure you at deeper depths (from 600 feet to 300 feet in 4 seconds) that this is an extremely traumatic experience.”
With this escape system the ascent to the surface will take around 4 minutes to cover the 600 ft. When a scuba diver is surfacing in stages, everything is controlled. But a submariner escaping a sunk submarine using the special suit will experience a rapid descent with zero control. In the 1987 example, there were a number of injuries. These included perforated eardrums and also the bends or decompression sickness. This is caused by nitrogen coming out of the bloodstream and forming bubbles, which leads to severe joint pain. The US Navy claims to be working on a new enhanced “Deep Escape System,” which would lead to a doubling of the current limit. One that would take them down to a depth of over 1,000 ft.
Many have proposed that the ideal deep escape method should revolve around an atmospheric diving suit. This is essentially a one-man submersible that isolates the wearer completely from the surrounding water pressure. They are commonly used when divers need to operate at depths of 2,000 feet and more. But as far as submarines go, the problem with these suits is that they are huge. As you can imagine, submarines have very limited space for storage. Right now, a new approach is being put into practice, which involves a combination of previously used techniques which is hoped will reduce the physiological stress the body will inevitably go through. Coupled with upgraded hardware, it's hoped that a solution can be found in order to give submariners a better chance of escaping a sinking or sunken submarine.
Even surviving a few minutes under extreme pressure is going to be very difficult. If you saw the James Cameron movie, “The Abyss”, he featured “liquid breathing.” Essentially the submariner’s lungs are filled with an oxygen saturated liquid that cannot be affected by the outside pressure. Though this sounds crazy, it's not science fiction. As the technique has been investigated and used by both US and Russian naval researchers. A commercial diver called Frank Falejczyk what's the very first man to breathe this oxygen filled liquid. Later on James Cameron saw a presentation from the diver and decided to make use of this technique in his movie.
Sadly the wreck of the KRI Nanggala-402, was finally discovered resting on the seabed at around 3000 feet. This would have been much too deep for any present-day escape systems. The submarine also appeared to have broken apart, which would reduce the possibility of survivors to virtually zero. In spite of this, photos and video taken from inside the sunken vessel did show escape suits floating around in the darkness. This means that even at these depths, probably the submariners were grasping at any straws that might result in being saved. In such a desperate situation everything is worth trying.