What is the future of pressurised submarine escape training?

By Frank Owen

Although there has been no (formal) public statement, it’s understood that the Royal Australian Navy (RAN) has revised its long-standing program to conduct pressurised submarine escape training (PSET). Any decision to cancel this in-country training would not have been taken lightly, so let’s consider the issues that would (or should) been considered.

Why is a submarine different?

Submarines are deadly machines. As Rear Admiral Peter Briggs has postulated in his paper “Strategic Sting”, their stealth makes them ideal instruments of foreign policy and, akin to a floating minefield, they demand a disproportionate level of resource to neutralise their effect. It is for this reason that more nations than ever before have started adding them to their orders of battle. These features also make them objects of fascination to the wider public.

Little wonder, then, that the loss of a submarine grips the world’s attention like few other accidents. They generate a feeling of helplessness in much the same way as situations where miners are stuck several hundred metres beneath the surface. Some examples of peacetime incidents where the submariners survived the initial accident are:

• USS Squalus. This submarine sank in 243 feet of water in September 1939 due to the mechanical failure of a valve indicator. All 33 of the survivors were rescued using what is known as a Submarine Rescue Chamber (SRC), versions of which are still in service.
• A short time later, HMS Thetis sank just outside Liverpool, UK, following flooding through a torpedo tube. Despite being so close to the surface that the stern was able to be lifted clear, 97 of the 101 on board perished because one of the escapers became trapped in the escape tower.



HMS Thetis

• In 1953, HMS Truculent sank in the River Thames estuary following a collision and, although 64 of those that survived the accident made a successful escape, all were swept away by the strong currents and 57 died from exposure.
• The Peruvian submarine BAP Pacocha sank in August 1988 following a collision with a fishing trawler. Before it sank, 33 managed to abandon the submarine, but several of the 22 trapped inside the submarine suffered injuries, some fatal, because of their unfamiliarity with the escape systems. Notably, this lack of familiarity arose because of a cost-saving measure by the Peruvian Government to stop submarine escape training.
• Perhaps the most reported accident of the modern era was of the Russian submarine Kursk which, in August 2000, sank following massive explosions of her own torpedoes. The 23 survivors, trapped in an after-compartment that subsequently suffered heavy leaks from around the propeller shafts, were unable to be rescued and were at a depth beyond the capability of the Russian escape system. Sadly, the compartment flooded before any intervention was possible and all 23 perished.

When the worst happens…

A submarine is in trouble. As crew members struggle to keep their submarine afloat or maintain their depth, there may be sufficient time for some, or all, personnel to abandon ship on the surface. Once the submarine sinks (and can no longer surface), it is termed a “Distressed Submarine” (DISSUB). Conditions inside the DISSUB are likely to be fraught for those who have survived the initial accident. Mechanical systems that once controlled air temperature and quality are likely to be without electrical supply. The temperature of the DISSUB will fall to that of the surrounding seawater within a couple of days.

Emergency systems on board can control the two fundamental gases of oxygen and carbon dioxide within survivable limits for a few days, provided those systems remain operational. The internal pressure of the DISSUB is likely to be elevated because of the water that has almost certainly flooded into the submarine. Injuries will be a further complication for the survivors, especially if the accident has involved collision with another vessel or object.

Those inside are faced with decisions that will drastically affect their chances of survival. The choice of whether to attempt escape or await rescue by surface forces is heavily influenced by the conditions on board. Where the situation is deteriorating rapidly, escape may be the only option.

The decision to attempt an escape is a challenging one for the person termed the “Senior Survivor’”. Submarines today are fitted with systems that have been tested down to 180m, a depth equating the edge of the continental shelf, however, the risks increase with depth and operational guidance now recommends that attempting to escape at depths below 150m should only be undertaken as the last resort.

How does it work?

In simple terms, the escape system involves being equipped with a suit that incorporates a venting life jacket and a hood to contain the vented (and exhaled) air which keeps the head in air so that the escaper can continue to breathe “normally”. The escape is performed via a specially equipped airlock (the escape tower) that can be flooded in a short enough time to prevent nitrogen being absorbed into the bloodstream. At the same time, an inflation system provides air into the life jacket at a pressure that is continuously above the pressure inside the tower as it floods. Once the water pressure inside the tower is the same as the sea pressure outside, a spring in the upper hatch overcomes the sea pressure that has been holding it shut and the escaper floats to the surface.

The rate of change of pressure during flooding up is very significant. Equalisation needs to occur very rapidly if “the bends” are to be avoided and, at great depths, it’s likely that the escapers won’t be able to keep “clearing” their ears. This means that their ear drums may burst which is excruciatingly painful and can distract the escaper from the more critical message about the need to breathe.

The ascent itself is very rapid (it reaches about 2-3 metres per second) but it’s cold and dark until you approach the surface. Those who have experienced escape at depth describe a simple and relatively comfortable experience when escaping down to about 90m but beyond that, it gets physically harder and, from about 150m, something that’s increasingly risky (and frightening), especially in the tower itself.

What’s the History of PSET?

In 1946, Captain P. Ruck-Keene conducted a review of submarine escape for the Admiralty using the evidence of submariners who had escaped from submarines sunk immediately prior to and during World War II. While the report is some 72 years old, it contains data from a large number of successful and failed escapes from sunken submarines. We are very fortunate that there has not been a lot of data available in this area since then.

The report makes a number of relevant points:

• The survivors in a sunken submarine contemplating escape “… must be regarded as quite incapable of doing anything but the simplest tasks. They are frightened, numb and stupid.”
• 99 of the 103 people in HMS Thetis were killed because the fifth person to escape from the submarine panicked, did not follow the correct procedure in the escape tower, died and in the process rendered the escape tower inoperable so that none of the other survivors in the submarine could escape.
• The committee recommended pressurised submarine escape training with the highest possible levels of fidelity. “… throughout the war, disasters and mistakes were almost entirely due to ignorance of simple physiological facts and lack of knowledge of how to use the equipment”. “No matter how simple the equipment is, successful escapes will never take place without proper training and knowledge”.

A stark reminder from the Ruck-Keene report for today’s submariner is that in war, waiting to be rescued from a sunken submarine is not an option. If one’s submarine is sunk in an operational area, escape is the only way out.

The training facility

For the escape to be successful, all those involved need to be trained and, most importantly, confident that the system works. Up until now, that has consisted of a combination of theoretical and practical training using a purpose-built Submarine Escape Training Facility (SETF); a tower containing a 22m deep water column with an escape tower at its base. The SETF was built at HMAS Stirling in Western Australia in the mid-1980s and has long been regarded as one of the best in the world.

The SETF is now over 30 years old and will need some investment if its systems are to be operated to the same levels of its original design. There have been periods where training was suspended because of mandatory system maintenance activities. While the annual costs of its operation and maintenance are believed to be less than $10 million, in the context of the reported $1 billion spent on submarine sustainment, this is not significant. How else can the Government meet its own obligations to provide a safe means of egress from the workplace?

Apart from some training accreditation shortfalls, partly due to the in-water instructors being exposed to high pressure levels through a combination of personal and professional diving, the rate of accidents has been remarkably low. Turkish research, for example, reported 41,183 training ascents from 30 and 60 feet without serious injury. This low escape training accident rate is also evident in other countries such as the United States, Australia, Canada, Japan, and Germany so it is possible that the Australian Navy’s decision to close the SETF is based on another factor.

In 1999, a paper by (then) LCDR Robyn Walker RAN (now Surgeon-General of the Australian Defence Force) described the Australian submarine escape and rescue organisation, stating that “…the RAN has an obligation to make every practicable effort to provide the safest work environment for its personnel”. In that same year, Occupational Health & Safety Assessment #29 into Pressurised Submarine Escape Training recommended the continuation of PSET and this was accepted by the RAN SUBSAFE Board. Sadly, the report appears not to have been published although the author retains a copy of the draft.

The training experience

The theoretical training involves comprehensive training in the mechanical systems and procedures that are fully aligned with the principles of competency-based training and assessment (CBTA). CBTA, of course, is unable to replicate the physical and psychological environment of a submarine accident so one hopes that the messages conveyed during the training are strong enough to remain in place when stress levels are extreme.

After some medical tests to check your ears and lung capacity, all of this is put into place with practical, experiential training by actually making an ascent from the tower at its base to the surface of the SETF water column. Throughout this ascent, the students are fully supervised by in-water instructors who can monitor and intervene if the student is not following the correct procedure. If everything goes well (and it’s all designed to), it’s a lot of fun and something you never forget.

The most important message that I took away from my own experience of escape training was never to hold my breath. This is a very real application of Boyle’s Law where the volume of air in your lungs increases as you come shallow. The most difficult part is the final 10 metres where the air volume doubles and, if you haven’t sorted out your breathing (or continuous exhaling if the suit hood has got ripped), you are very likely to burst your lungs (or more correctly, suffer from Pulmonary Over-Inflation Syndrome). To demonstrate this during training, a wine cask bladder is released from the base of the escape tank. No matter how little air is in it at the start, the bladder invariably bursts as it approaches the surface.

While it is relatively simple to remember to keep breathing, it is unnatural to just blow out because our instinct is that if we blow out, we then have to breathe in. The body cannot expel all the air in its lungs and it’s at that time that Boyle’s Law kicks in, increasing the lung’s air volume in inverse proportion to the pressure and the practical training provides that lesson. A student can be told time and time again not to hold his or her breath, but the number of students who have to receive a jab in the abdomen while actually in the water to remind them to breathe demonstrates the difficulty of applying lessons from the classroom into a different environment.

Conclusion

While everyone who has any connection with submarines hopes that the need for a real escape from a sunken submarine will never arise, it would be a great concern if the first time a submariner has the physical and psychological experience of escape is in the dark, in cold water, with no instructor support and when the escapee’s life (and that of his or her colleagues) depends on his or her capacity to remember the drill. Should the escaping submariner fail in this process and block the escape route, the members of the crew remaining in the submarine are then likely to be fatally trapped.

The process of the submarine escape process clearly contains risks; some during training and many in the actual escape. It may be possible to avoid the training risks but that merely transfers them to the poor sod next in line to climb into the escape tower for real. As an under-water medicine doctor said to me in 1999, the risks of doing escape training are far less than the risks of NOT doing escape training.

Frank Owen OAM is a former submarine officer who introduced the Australian submarine rescue vehicle “Remora” as Director of the Submarine Escape and Rescue Project. He retains an active interest in all aspects of submarine escape and rescue.