A Very Short History of Saturation Diving

by James Vorosmarti, Jr., MD

Reproduced from Historical Diving Times Issue 20 (Winter 1997)

In 1962 it was my great fortune to apply for and be accepted into the Navy submarine and diving training programme. Unbeknown to me at the time this was the beginning of the recent 'Golden Age' of diving with the advent of saturation diving and extensive activity around the world of diving medical research and advances in diving equipment. This brought me into the United States Navy SEALAB programme. I never realised it until I was preparing my lecture on the history of saturation diving for the HDS Conference last year, that this allowed me to meet and work with the world famous (and infamous) personages of saturation diving and enabled me to count some of the 'greats' of diving research from the 1930s and 1940s as colleagues and friends. The purpose of this article is to publish a short history of saturation diving over the period from the late1950s to the early 1970s.

Saturation diving is defined as the situation where one is at a depth or pressure for a long enough period of time (12 hours or longer) to have the partial pressures of the dissolved gases in the body at equilibrium with the partial pressure of those in the ambient atmosphere.

This concept was not a new one. Haldane, Boycott and Damant in their 1907 report were well aware of the fact that saturation would occur. At pressures up to 45 psi, or four atmospheres of absolute pressure, there appears to be no substantial objection to keeping men for six hours, or even more, continuously under pressure, provided that the mode of decompression is safe.

However, there is no clue in these writings that they ever considered the practice of saturation diving. I think that the most obvious reason is that there was simply no foreseeable need for this technique at the time. Most diving was done at less than 50ft and certainly diving deeper than 100ft was rare. Most jobs did not require long bottom times so decompression was not excessively long. Even in tunnel work, decompression time was not overly long except when working at the highest pressures. Another reason was that Haldane, et al were concentrating on surface supplied diving for the navy. No equipment for this type of saturation diving existed then, although construction of an underwater habitat would have posed little problem with the engineering knowledge of the time. Atmosphere control however, would have posed an almost impossible problem because of the inability to easily and accurately monitor gas composition. Temperature control also would have proved to be a problem. Another clue to their awareness of saturation diving was shown in an exchange between Damant and Haldane in 1935 in a discussion of caisson decompression. Damant commented on Haldane's idea of extending shifts to eight hours. He stated that "a complete table from hour to infinity is the thing (required) - as you have drafted it". Again there was no real need to extend the tables for long bottom times, but the idea was certainly there.

Another close miss with saturation diving is illustrated by the underwater diving station proposed by Davis. Unfortunately, there is no date attached to this idea but it was probably devised in the 1920s or 1930s. It is obvious that Davis was thinking ahead to having divers live, at least for short periods of time, probably days, under the sea. The problem here is that the habitat is maintained at one atmosphere so that the diver still would have required decompression. Why was this not adapted for staying or living at ambient pressure? Again, probably because there was no real need.

FIRST SATURATION DIVE

The first intentional saturation dive (although not called that at the time) was done in December 1938 (1). It was planned by Dr Edgar End with Max Nohl as the diver. The dive was done because of problems with animals not humans. At the time tunnelling operations were underway in Milwaukee and mules and donkeys were used for hauling material. They were kept under pressure for weeks and months at a time. However, whenever decompression of them took place they died. The details of the decompression schedules used are unfortunately not available.

Therefore this dive was planned to demonstrate that animals (and humans) could be decompressed after extended periods of time at pressure. Nohl entered the chamber at 1100 on or around December 19th (the record is not clear on the exact date) and spent 27 hours at a depth of 100ft breathing air. End spent about 11 hours in the chamber doing physiological testing, the results of which are not available as no report was ever published. Decompression took about five hours and resulted in Nohl suffering decompression sickness on reaching the surface. He recovered fully after recompression treatment except for feeling bad for several days afterwards. We now know that this was probably due to a combination of the decompression sickness and pulmonary oxygen toxicity from the long period of breathing a high partial pressure of oxygen. Two conclusions reached by End, at least as reported by Look Magazine, were that 27 hours was the limit for staying under pressure without risking life, and that helium substituted for nitrogen in the breathing mix may reduce diving hazards.

A few years later, in 1942, Dr Al Behnke stated the first clear concept of saturation diving with excursions. In an article published that year in the Medical Clinics of North America (2) discussing working at 50 psi he wrote, "It would appear advisable therefore to keep men at work on a job continually under pressure. Following a work shift at maximum pressure, the pressure could be lowered rapidly to between 20 and 30 pounds and maintained at this level during the rest and sleep period. The final decompression prior to emergence into a normal atmosphere would be uniform over a period of 8 to 24 hours". He also made a statement in this article that prolonged exposure for up to seven days at pressures of 30 psi gauge had been made repeatedly. Presumably he was referring to tunnel or caisson work. Unfortunately he gives no reference for this statement. At the time there had been a fair number of experimental exposures to 90fsw for 9 to 12 hours. However, using the current definition of saturation these are not considered saturation dives. He was certainly familiar with the exposure of the survivors of the USS Squalus sinking as he was the on-scene medical officer. These sailors were at a pressure of 27fsw for over 24 hours. They were brought directly to the surface without any cases of decompression sickness.

The term 'saturation dive' was used for the first time in 1945 by Dr Otto van der Aue. He was working at the USN Experimental Diving Unit conducting a large series of experimental dives in order to produce acceptable surface decompression schedules. These dives were done to test the still used 2:1 ratio for safe decompression. The decompression schedules were the first in which a tissue half-time of 120 minutes was used in their calculation. Tissue half-time refers to the mathematical concept of dividing the body into a series of hypothetical components called tissue compartments. Tissue half-time refers to the hypothetical time required for a tissue to gain or lose one half of the inert gas dissolved in it, or which could be dissolved into it. It is a concept used for the mathematical construction of decompression schedules not for correlation with any specific anatomic tissue and does not correlate to any body tissue. As part of this series four dives were done which were called, and actually were, saturation dives. All were done in October 1945 with air. The first was to 33ft for 24 hours with direct surfacing. No cases of DCS resulted in the four divers. The next two dives were to 33ft for 36 hours with 4 divers in each exposure. Two of the divers developed bends. The last dive was to 99ft for 12 hours followed by decompression to 33ft for a stay of 24 hours. Both the divers using this schedule suffered DCS. The conclusion was that for decompression from longer dives long half-time tissues needed to be assigned lower ratios than short half-time tissues. In other words, the 2:1 ratio for decompression did not work (as Haldane had already discovered).

No more was heard about saturation diving until 1954 when, for reasons that are obscure, a diver named Ed Fisher stayed underwater at 33ft for 24 hours beginning on August 21st. This event took place in Florida, and he did this without the benefit of anything but his wetsuit, an inflated inner tube anchored to coral and the support of friends who brought him replacement air tanks and food from a support boat nearby. He reportedly also speared a fish and ate it raw for dinner. He decompressed at 10ft for 15 minutes, although he did not think this was necessary, and reached the surface with no problems. In an interview, he said that the only problem he had was the pain when he had to remove his wetsuit. Surprisingly he did not peel off any skin with his wetsuit!

GENESIS

There was no activity in saturation diving until 1957 when Dr George Bond, Dr Walter Mazzone, and Dr Robert Workman began to explore new approaches to inner space exploitation at the Naval Submarine Research Laboratory in New London, Connecticut. They began with a series of animal experiments to ascertain what, if any, were the results of exposures in various animals to normal air and synthetic atmospheres at a pressure of 200fsw. These experiments were called Genesis. The original material documenting these experiments are not available and most of them were not published in a scientific format. I have relied on the description by Dr J Miller and Ian Koblick as published in their book, Living and Working in the Sea, for the following naming and chronological order of these studies (3). The first study, Genesis A1, exposed rats at 198fsw on air. All died in 35 hours from oxygen toxicity, which although expected, was not a very auspicious beginning. This experiment was a follow-on of some animal saturation experiments done in 1932 by FJC Smith, JW Heim, G Bennett, RM Thompson, and CK Drinker at Harvard who were interested in oxygen toxicity (4). In those experiments rats were exposed to air at 5atm for up to 72 days. Those rats could be called the first mammalian saturation divers. Bond, et al were familiar with this work which was published in the Journal of Experimental Medicine.

In Genesis A2, rats were exposed to a normoxic nitrogen-oxygen mixture at 198fsw for 14 days. All but one survived, but all showed lesions in the lungs. The cause of these lesions was unknown. Genesis A3 rats were exposed to pure oxygen at 45fsw which provided the same oxygen partial pressure as in the A1 exposure (1.5 atm). As expected, all rats died due to oxygen toxicity, again in 35 hours. The next step was to show that rats could survive in a synthetic atmosphere of heliox with 20% oxygen. This exposure, Genesis B1, took place at 1atm and no adverse effects were found after 16 days. Rats were again exposed in Genesis B2 at 200fsw for 14 days. No adverse effects were seen even on life span or breeding. From 1959 - 1961 four more species, including goats and monkeys were exposed to normoxic gas mixtures at 200fsw with the production of no physiological problems.

Genesis C began in 1962 after the Secretary of the Navy finally gave permission to expose humans to a synthetic atmosphere at pressure. Two Medical Officers, John Bull and Albert Fisher, and Chief Quartermaster Bob Barth spent 6 days in a helium-oxygen atmosphere at one atmosphere absolute. This was done at the Naval Medical Research Institute in Bethesda, MD. The problem of thermal control and comfort in a helium atmosphere was discovered on this exposure. The Medical Officer was Charles Aquadro, who later left the US Navy and worked for years with Cousteau in his endeavours in undersea living. Finally, in April 1963, in the Navy Experimental Diving Unit in Washington, DC, three humans were exposed to prolonged pressure in a helium environment (Genesis D). Barth and Bull were joined by Raymond Lavois, another Navy diver, in a dive to 100fsw for 6 days in an atmosphere of 7% nitrogen, 7% oxygen, balance helium. This was the first helium oxygen exposure to take place which lasted for more than a few hours at pressure. No studies showed any deviations from normal, but the thermal problem was again noted and the problem of communication when breathing helium was exacerbated by the increased pressure.

The final Genesis phase, Genesis E, took place in August and September 1964. Bull, Barth, and Chief Hospital Corpsman Sanders Manning were pressurised to 198fsw for twelve days in a chamber at the Submarine Medical Research Laboratory in New London. During this dive, in addition to the thermal and communication problem, the divers were made more uncomfortable by the high humidity. Once again, the physiological studies showed no adverse effects as a result of this exposure.

At this juncture, so as not to raise any old stories about individuals stealing from others, I would point out that from 1957 onwards Bond, Mazzone, and Workman had full discussions with Cousteau about the Genesis team's ideas and experimental results, and that Cousteau has always given credit to Bond for the idea of saturation diving. Later, Ed Link was also a party to these discussions and results.

MAN-IN-THE-SEA I

Link was the first actually to organise an 'at sea' saturation dive. As part of his Man-In-The-Sea programme he devised a chamber which could be used as very cramped living quarters at depth, and could be sealed for retrieval to a ship with subsequent decompression of the diver on board. Robert Stenuit was the diver and he began the dive on September 6, 1962 at 200ft off Villefranche on the French Riviera. Link himself had made several trial dives to check out the equipment but none was longer than 8 hours and the deepest depth was 60fsw. The dive duration was planned to have been 48 hours. Unfortunately, a combination of helium leaks, the sinking of the boat with additional helium supplies and bad weather, caused the experiment to be terminated after only 24 hours. Stenuit required treatment for decompression sickness of his right wrist.

Sometime in the 1920s or 1930s Davis developed the Transfer-Under-Pressure (TUP) system. This allowed the diver to be transported to and from a shipboard chamber to a work site under water and allowed him to be brought to the surface either while beginning decompression or decompressing after the transfer to the shipboard chamber. Anyone familiar with modern saturation systems will recognise that the principles are those used in current saturation diving. Link's Man-In-The-Sea system is certainly very similar in appearance and utilisation to the Davis TUP system. This again points up the fact that saturation diving would have been possible well before it was finally developed into the technique as we know it today.

CONSHELF

Cousteau, on September 14, 1962, began the first of his series of experiments in saturation diving and living in the sea. Conshelf I took place about 100 miles from Link's experiment. The habitat in which Albert Falco and Claude Wesley lived for seven days, was a large cylinder (called Diogenes) anchored in 10 metres of water. The atmosphere was air in both the habitat and the breathing apparatus. They made frequent dives and made at least one excursion to 180 metres.

Conshelf II followed shortly thereafter in June 1963. This was a much more ambitious operation with two habitats, Starfish House and Deep Cabin. The site was in the Red Sea near Port Sudan. Starfish House was located at a depth of about 11 meters and was again supplied with an atmosphere of air. It was large, and had spacious living and diving quarters. Deep Cabin was a large upright cylinder with three levels, the upper two of which were living quarters and the one below a diving centre. Five divers spent 4 weeks in Starfish House. Two divers lived in Deep Cabin for 1 week at a depth of about 27 metres. They breathed a mixture of 50% helium and 50% air. During their stay they made several excursions to 110 metres. Deep Cabin had several problems including leaks, breaking cables and, the most serious, a tendency to slide off the ledge on which it was moored. It was finally securely anchored, but not before falling once with the divers in it. These divers can be considered as the first to have truly lived in the undersea environment, as they did all their own cooking and were a part of the underwater world.

MAN-IN-THE-SEA II

Man-In-The-Sea II was planned by Link to extend the depth at which humans could live underwater. This was an experiment at 400fsw, and was based on the results of several US Navy exposures to 400fsw for 24 hours conducted in late 1963. For this trial Link built a collapsible habitat that could be easily lowered over the side of a ship. The SPID, for Submersible Portable Inflatable Dwelling, was an 8x4ft inflatable bag on a steel frame anchored to a ballast tray. In June 1964 it was lowered to the bottom at 415 feet in the Bahamas. Robert Stenuit and Jon Lindbergh were lowered to the SPID in a Submersible Decompression Chamber (SDC) (shades of the Davis TUP). They spent 49 hours in the helium-oxygen atmosphere before decompression. They also had a range of equipment problems to overcome, but the major difficulty was hypothermia caused by the helium-oxygen atmosphere.

SEALAB I

The first US Navy habitat operation, SEALAB I, began shortly afterwards, in July 1964. This was a scheduled three week stay for four divers, Barth, Manning, Anderson and Thompson, at a depth of 193 feet. The habitat reflected the level of funding for the project, as it was constructed of two salvaged harbour security net floats and ballasted with railroad car axles. It was located about 26 miles off Bermuda near Argus Island, a man-made tower from which the operation was supported. In contrast to the earlier experiments this was planned as a full scale investigation of human physiology underwater. Unfortunately, it had to be terminated after 11 days because of an approaching tropical storm. Decompression was to have been done by raising the habitat with the divers in it. At a depth of 81 feet they had to leave the habitat because the increasing sea state made it impossible to continue to handle the habitat safely. They swam out to the SDC which was raised to the deck of the tower and completed the remaining 56 hours of decompression in the extremely tight and uncomfortable quarters provided by that equipment. One can only imagine the state of hygiene of the divers and the SDC when the hatch was finally opened!

SEALAB II

This was a much more ambitious programme than any up to this point, involving even more physiological testing and a busy underwater programme testing new methods of salvage, new tools, an electrically heated drysuit, porpoise training and work, and behavioural studies. A completely new habitat was built with all modern conveniences and an adequate support ship was provided. Beginning on August 28, 1965, three teams of divers spent 10 -16 days each at a depth of 205 feet in the La Jolla canyon off Scripps Institute of Oceanography in California. One of the aquanauts, Scott Carpenter, ex-astronaut, stayed on the bottom through two team shifts. Three unusual events occurred during his stay. A conversation was held between Carpenter and astronaut Gordon Cooper who was circling the globe at the time in the Gemini space capsule. Later aquanauts Griggs and Sheats spoke to oceanauts Cousteau and Lebon in Conshelf II. As part of the public relations effort, it had been arranged that Scott would speak to President Johnson. Dr Bond was speaking to a White House operator setting up the call and explained to her that Scott was in a chamber filled with helium gas, and therefore, his voice would sound very funny. The operator said that the President did not speak to persons in gas chambers and immediately hung up! Needless to say the connection was finally made, but it was obvious that the President had no idea what Scott was saying in helium speech. However, the PR people were happy!

CONSHELF III

This experiment followed many animal dives and a manned chamber dive by Dr Chouteau and Dr Aquadro to 400 feet, plus a trial dive in Monaco harbour. It began in September 1965 when the habitat reached the bottom off Cap Ferrat at a depth of 328 feet. A six-man team spent 22 days on the bottom although it was planned to be only a 14 day experiment. I suppose that after the previous near disasters things were going so well that a good thing should not be wasted. The habitat was a large two-storey sphere which rested on a barge containing the ballast systems for raising and lowering the whole, along with two three-man hyperbaric lifeboats. These could be entered at pressure and released to the surface in case of emergency. The upper floor was for dining, communications and data gathering. The lower level contained the sleeping, sanitation and diving areas. As with other habitats and saturation experiments there were many equipment problems all of which were overcome by the aquanauts themselves. This experiment was unique in that an oil well Christmas tree was lowered near the habitat so that the divers could test actual practical techniques.

GLAUCUS

In order to relieve readers of any anxiety that the US and France were the only two countries in which active saturation dives were being done, at the same time the above two experiments were taking place, the Bournemouth branch of the British Sub-Aqua Club upheld British honour by conducting a saturation dive in Plymouth Sound at a depth of 38 feet of water. Two divers, Colin Irwin and John Heath, spent one week in Glaucus beginning 16 September 1965. The habitat was a small cylinder mounted on a ballast pan. In fact, it appears to have been a smaller and less luxurious version of the SEALAB I habitat. Food and supplies were provided by team of topside support divers who also had to operate in less than adequate conditions. All survived in spite of a short but severe storm which threatened the experiment on the second day. What was proven was that motivated divers could survive in a habitat that was very cheaply put together, but that it was not a pleasant experience, nor could any real science be undertaken in that type of situation.

CACHALOT

This was the first commercial saturation diving system and was designed by Westinghouse Electric Corporation, Underseas Division (Tom O'Neill and Alan Krassburg) for use in clearing the trash rack of the Smith Mountain Dam in Virginia. The system consisted of a large chamber Deck Decompression Chamber or DDC and a Personnel Transfer Capsule (PTC) which could be mated to the DDC at pressure. The divers lived in the DDC and went back and forth to work in the PTC. The operation was between depths of 159 and 240 feet and lasted for four months beginning in August 1965. To do the job using contemporary conventional techniques would have entailed draining the whole reservoir, a two year job. To do the job using two divers at a time from saturation replaced 32 divers using normal surface diving techniques. This system was the forerunner of the great explosion of commercial diving systems which soon spread across the world. In fact, the first at sea commercial saturation dive was done in 1966 in the Gulf of Mexico using this same system.

SEALAB III

This was the most ambitious of the habitat programmes, with work-up dives and biomedical studies, beginning in 1966. These dives were done a the US Navy Experimental Diving Unit in the Washington DC Navy Yard and ranged in depth from 250 to 1025 feet. Most dives included studies of the divers' medical status. For example, there were respiratory studies using high density gases at pressure to simulate heliox at much higher pressures, exercise studies, behavioural studies and work on overcoming the problem of helium speech. Even the studiers were studied. The habitat used in this experiment was that of SEALAB II, which was refurbished. The support craft was the USS Elk River which carried the new double Mk2 saturation diving system and which had been reconfigured to include a moon pool. This was an opening through the centre of the ship allowing the PTC to enter the water in a protected area and thus cut down on the problems of handling a large pendulum in rough seas. Two vans on the deck were completely outfitted as medical and command vans. The medical van was in fact an up-to-date medical laboratory in which we did almost every test that a major hospital could do and then some, plus all the atmosphere monitoring for the chambers, PTCs and habitat. Diving sets were semi-closed mixed-gas rigs. Five teams of eight divers were to spend 12 days each on the bottom at a depth of 610 feet doing all sorts of tasks including testing new salvage techniques, oceanographic studies, fishery studies, and so on. This was a joint military and civilian programme and included military divers from the UK, Canada and Australia. Philippe Cousteau was also to have been member of one of the teams.

Because of all the different experiments to be done, a lot of bottom time was needed and an umbilical had been designed which was neutrally buoyant to allow the divers to work up to 600 feet away from the habitat. One problem was that the cold water made these very stiff, so trying to pull one to its full length would have been a tough, if not impossible, job. One of the most experienced aquanauts said that if the people topside thought he was going to ever be more than an arm's length away from the habitat let alone 600 feet, they were crazy! So much for prior planning.

The project was delayed by problems with the complex equipment involved and the habitat did not get lowered to the bottom off San Clemente Island until February 18, 1969. The habitat began to flood through what was later found to be an improperly installed electrical hull penetrator, and on a dive to attempt to get into the habitat to solve the problem one of the aquanauts, Barry Cannon, died of carbon dioxide poisoning. The grand experiment came to a halt. The habitat was salvaged with the help of lots of air from a submarine's high pressure air banks only to be later scrapped. The Navy never again attempted further experiments of this kind, although Navy saturation diving continued until recently. Unfortunately the US Navy, the pioneer in saturation diving, no longer has this capability in the fleet.

TEKTITE

This was a joint effort between NASA, the Department of Interior and the US Navy. Basic studies were designed to study small crew behaviour during isolation over an extended period of time, and the use of nitrogen-oxygen for long exposures. The habitat consisted of two cylinders joined together and placed on end. These were ballasted to be 10 tons heavy. It began operation on 15 February 1969 in Greater Lameshur Bay at St John, Virgin Islands. Decompression was completed on 15 April 1969. Four divers from the Department of the Interior spent this time at 43 feet doing biological studies on the reef life and being spied upon by the behavioural scientists. After the failure of SEALAB III some of the SEALAB crew were sent to provide support and I ended up being a watch officer for several weeks. Living conditions were primitive and there was little to do because of the isolation of the site. About the only fun was to call an emergency drill in the wee hours of the morning and get the camp commander excited.

About 60 habitats were built world-wide, and although the era of habitat diving has long since finished, the active field of commercial saturation diving has spread throughout the world. One habitat that survives is La Chalupa. This was built in 1972 and used for undersea research until 1974. It now is part of the Marine Resources Development Foundation and is known as the Jules Verne Lodge. It is fitted out as an underwater hotel room where one can spend 23 hours at about 30 feet whether an aquanaut or not. This foundation also uses another old habitat, Aquarius, as an underwater classroom.

The real explosion in saturation diving came with the many different commercial systems, ranging from a small portable system to be used on a ship as required, to the huge system built by Shell for use on a semi-submersible platform.

Because of the limits on space I have not discussed many of the contributions made to saturation diving by the Royal Navy and the French Navy and various diving companies such as Comex. During the late 1960s and during the 1970s these groups made many experimental dives to extend the depth at which working dives can be made. For instance, between September 1972 and November 1974, 28 saturation dives to depths of 250 metres were done at the Admiralty Deep Trials Unit at the Royal Naval Physiological Laboratory for proving decompression tables and doing physiological research. Diving companies, research facilities and universities pioneered the use of trimix and, more recently, the addition of hydrogen to the breathing mix in a continuing (albeit at a much lower level) quest to allow man to spend more time in the oceans.

1. Look Magazine, March 28, 1939.

2. Behnke A, Effects of High Pressures: Prevention and Treatment of Compressed Gas Illness, Med Clincs N.A., pp 1212 - 1237, July 1942.

3. Miller, JW and Koblick, IG, Living and Working in the Sea, 1st Edition, Van Nostrand Reinhold Co. New York, 1984.

4. Smith FJC, Bennett, GA, Heim, JW, Thompson, RM, Drinker, CK : Morphological Changes in the Lungs of Rats Living Under Compressed Air Conditions, J.Exp.Med, 56:79-89, 1932.