Jul 23

Sealab I

Monday, July 23, 2012 9:36 AM

Sealab 1 being lowered into the water from alongside the pier at the U.S. Naval Station Bermuda, July 1964.

Sealab I was the first experimental underwater habitat developed by the Navy to research the psychological and physiological strain of extended periods spent living and working underwater. Two more Sealab experiments followed the first, providing information that helped advance the science of deep sea diving and rescue. The following article, published in the February 1965 issue of Proceedings, discusses the goals of Sealab 1, and the results of the ten day experiment.

SEALAB I

by Lieutenant Commander Don Groves, U.S. Naval Reserve

An odd looking, 40-foot vessel, equipped with pontoon-shaped appendages, was launched from the navy’s oceanographic research tower, Argus Island, on 20 July 1964. Instead of floating, this vessel-the Sealab I-promptly sank to the bottom, 192 feet below the surface. Twelve hours later, four navy divers entered the Sealab 1, prepared to begin a unique 21-day experiment. Their assigment was to participate inthe Navy’s first protracted physiological-engineering test to determine how men can work freely and for extended periods in the hostile underwater environment.

Because of an approaching storm, the experiment had to be cut short after ten days of working in and around the ocean floor sea laboratory. In spite of this curtailment, however, all the experimental ovjectives of the project were accomplished. Moreover, othrough the man-in-the-sea, or Sealab, experiment, it has been concluded that total saturation dives in this depth in the open sea are now completely feasible.

History contains many accounts of man’s ingenious exploits underwater. Not too surprisingly, most of those, including such early inner-sapce ventures as the use of divers by Xerxes, the Persian King, (486-465 B.C>) and the employment of a diving bell by Alexander the Great in 332 B.C. have been connected with naval warfare.

Despite this 2,450-year history of underwater diving and swimming, man’s knowledge about his own physiological reactions to much of the diving envrionment and of the environment itself remains inadequate for his needs. for, while man is avle now to swim underwater with his Self Contained Underwater Breathing Apparatus, the duration and depth (100 feet or less) limitation imposed upon him by the availability of self-transported gas have not been improved greatly in the 34 years since SCUBA was first introduced.

This is particularly unfortunate since improvements to the diver’s staying power underwater and especially an improvement in his ability to operate at deeper depths would greatly enhance his capability of performing work which can be accomplished most economically and most rapidly by man. The existent situation might best be described by saying that in the Navy’s operational SCUBA work, so far, we have only really succeeded in removing the divers’ umbilical gas line to the surface. But we have yet to sever the “cord” of our past engineering and physiological concepts which binds us to a daily one-atmosphere (14.7 psi) surface existence. Project Sealab could be the cimitar which slashes this restricting cord.

The Sealab project is intended to demonstrate that the need for time-wasting, dangerous, daily decompression returns to the surface would be eliminated if an underwater worker could be provided with a pressurized, habitable shelter near his work. Inside such a shelter, a breathable gas (i.e, at 200-foot depth, a nominal mixture of 4 per cent oxygen, 16 per cent nitrogen, and 80 per cent helium) maintained at a pressure equal to the hydrostatic working or diving pressure (at each 33 feet of depth the guage pressure increases by one atmosphere or 14.7 psi), could comfortably sustain a man-in-the-sea for weeks or months.

Aquanauts working on the bottom, then, would reach “saturation” or an equilibrium with their surroundings, within 24 hours. They could then stay pressurized indefinitely without further increasing their decompression requirement (viz., 27 hours decompression time needed by them to ascend from a 200-foot depth after saturation). Under conventional diving techniques, the time of decompression increases with the length of time spent on the bottom. For instance, a diver who spends 20 minutes at a 200-foot depth breathing a helium-oxygen mixture requires approximately one hour to return to the surface safely. The same man with 60 minutes’ working time at this depth needs two and a quarter hours to ascend.

The Navy, however, properly feels that the questions of how best to exploit this saturation concept which does away with the required daily returns to the surface, and how to determine the extent to which a man can be deployed in a pressurized home-away-from-home and still perform useful work are still questions which require careful study.

In spite of the recent, exemplary, and well-publicized undersea efforts of such pioneers as captain Jacques-Yves Cousteau and Edwin A. Link, the subject of such undersea activity can still largely be characterized as a general are of ignorance. This ignorance must soon be overcome, and man in 1965 is doing some thoughtful planning in this regard. Confronting him are a whole host of challenges: salvage, submarine rescue, underwater construction, underwater inspection and repair (cables, pipelines, etc.). Then, too, there are military considerations-ASW warning installations, coastal defenses, submarine bunkering stations-not to mention the potential economic benefits: ocean floor mining, fish and underwater crop farming, and oil, for example. Thus, more exploratory programs aimed at investigating just such possibilities are being planned.

How can man best be further interrelated with the ocean environment without the need for complete environmental separation such as he has in the bathyscaph Trieste II and our operational submarines? Where is this type of man vulnerable to the forces of nature-including those of the psyche? These are basic questions whose answers are of vital importance. They can be provided most authentically by laboratory experiments only such as Project Sealab.

Sealab I, crude though it someday will seem in retrospect, performed several important functions byond freeing men from the requirement of daily decompression. The project attempted to evaluate man’s capability for extensive underwater work by carrying out such tasks as:

  • Precision Bottom Charting and Mapping
  • Maring Biological Investigations
  • Structrual Inspection of the Argus Island Tower

And, of equal importance, Project Sealab evaluated the vessel, Sealab I, so that the engineering data obtained therefrom can be used in the design of Sealab II and, in follow-up experiments scheduled to be carried out subequently at 300-foot and 600-foot depths.

Behind the four Navy aquanauts when they entered Sealab I were two years of intensive training. (The three enlisted men and one officer who participated in the experiment were QMC Robert A. Barth, HMC Samders W. Manning, GM1 Lester E. Anderson, and Lieutenant Commander Robert E. Thompson, MC, U.S. Navy). Before that, such “Sea Daddies” as Captain George Bond, MC, U.S. Navy and others-notably personnel at the U.S. Naval Medical Research Laboratory at Groton, Connecticut-had been working since 1957 in hyperbaric physiology. Their work was aimed at providing new approaches to the old problem of the conquest of inner space. And the extensive pressure chamber studies by these Navy scientists had indicated that men could live in an artificial helium-oxygen atmosphere at a simulated depth of 200 feet for prolonged periods and not experience any harmful effects permanently.

Captain Bond, principal investigator for Sealab and most recently assigned to the Bureau of Naval Weapons’ Special Projects Group, characterizes some of the initial thinking as follows:

…At first, it appeared that two major problems were involved: the choice of respirable gas mixture at any depth; and the ultimate question of decompression. Initially, we sought to provide a respirable mixture which could minimize narcosis and breathing resitance alike; next, the problem of decompression after total body saturatio required resolution. Since the operational concept would involve exposure of man to gas pressures of up to 20 atmospheres…a great deal of basic work remained to be done…

After a series of tests by Dr. Bond in which a variety of animals were exposed to selected mixtures of helium, oxygen, and nitrogen, it had been found that the animals not only survived a 14-day exposure at a simulated depth of 200 feet, but that they could also be returned safely to surface pressures with no physiological damage.

When the animal tests were concluded in 1962, the Secretary of the Navy authorized the use of human beings in the tests. Accordingly, a group of volunteers was first exposed to an essentially nitrogen-free atmosphere for a total exposure of 144 hours. In this significant experiment, the average composition of the ambient atmisphere was 21.6 per cent oxygen, 74.4 per cent helium, and 4 per cent nitrogen. The next trials, using two of the men who later participated in Poject Sealab were run at a simulated 200-foot pressure depth.

Here, all major goals were achieved and the men withstood the exposure with no deleterious effects.

Buttressed by this formidable array of test results, then, Project Sealab became the first exploratory attempt to achieve the laboratory results under actual conditions. The Office of Naval Research in conjunction with Bureau of Ships, U.S. Naval Medical Research Laboratory, U.S. Naval Mine Defense Laboratory, the Experimental Diving Unit, the U.S. Navy Oceanographic Office, the U.S. Navy Underwater Sound Laboratory, and others were involved in the work.

Although the detailed findings, especially due to the limited time of the test, are not now as definitive and conclusive as they might be, some major conclusions have been drawn. In summary these are:

Communication and the speech acoustics of helium and oxygen. In the Sealab I atmosphere, the human voice acquired a difficult-to-understand “Donald Duck” sound. This is due to the higher speed of sound in helium and the effect it has on the resonanting quality of the body’s repiratory air spaces which control vocal sounds. Since these sounds are only about 25 per cent intelligible, the need to develop a means of making a diver-to-diver and diver-to-surface communication understandable was obvious.

It was found that a special filtering device-the U.S. Navy Applied Science Laboratory helium speech modifier-greatly improved the intelligibility of communications from the Sealab habitat to the surface control center, and no difficulty was encountered using a standard divers’ communications system from topside to the chamber below. Thus, the helium speech problem has been solved for the undersea habitat and now remains a major problem in communication between swimmer and swimmer, swimmer to habitat, and habitat to swimmer.

Aquanauts enjoying a meal in their undersea habitat Sealab 1 at a depth of 192', 20 miles southwest of Bermuda.

Effect of temperature (water). There is still a great deal to be learned about the effects of immersion in water-especially cold water-upon human beings. Water has a specific heat of about 1,000 times that of air. Hence, one cubic inch of water next to the skin can absorb 1,000 times more heat from the body than a comparable volume of air for a given increase in temperature. Moreover, the thermal conductivity of water is 25 times that of air, and body heat is therefore rapidly conducted away from the skin into the adjacent layer of water. The familiar “wet suit” of black rubber used in Project Sealab provided protection against such phenomena, but the efficiency of such suits seems to be significantly reduced by the fact that helium, which readily diffuses into and saturates this material, has a themral conductivity much greater than the air which normally fills the tiny voids in the foam. Unfortunately, if the foam were coated by a barrier layer impermeable to helium, the pressure at depth would flatten the material so much as to render it useless as an insulator. This problem area promises to loom larger in future experiments where colder water will certianly be encountered (the water around Sealab I was 68 degrees F). Thus, it appears that some means of artificially supplying heat to the swimmer may be needed at times-especially if we are to take maximum advantage of our developing capabilities to remain on the bottom for long period of time.

The thermodynamic properties of helium-oxygen mixtures. At high pressures, increased molucular availability multiplies the heat transfer problem. The thermal conductivity of helium is five times that of air and for a 200-foot level it was postulated that a maintained 90 degree F temperature in the helium-oxygen atmosphere of the Sealab I chamber would give the aquanaut approximately the same subjective comfort as a 70 degree F temperature does on the surface in air.

Sealab established that the aquanauts appeared to climatize within the chamber at a temperature between 85 degrees and 90 degrees with a minimum amount of discomfort; and the total heating requirements within the chamber were considerably lower than had been estimated earlier. This is not only due to the subjects becoming acclimatized in the chamber at a temperture lower than that expected, but also to the insulating qualities of the 16 per cent nitrogen present (the nominal gas mixture used was 4 per cent oxygen, 16 per cent nitrogen and 80 per cent helium).

Still, the humidity control in Sealab I was also found to be inadequate and additional humidity control will be required for experiments to follow.

Other Sealab I findings of interest include the fact that during the first four days of Sealab I exposure, the subjects were somewhat uncomfortable noting minor discomforts such as joint aches. These were not serious, and did not incapacitate the divers. However, such discomforts did contribute to the general slowdown of movement during this period. While this slowdown was not noticed by the subjects themselves, it was quite apparent to the topside monitoring personnel.

Too, a certain ammount of personality change in the divers had been expected and did occur. For even before Project Sealab, it had been observed that men who spend some time under the sea tend to become imperious. They talk, often without realizing it, as though they were the masters over all they survey below and above.

There appeared to be a significant increase in individual susceptibility to nitrogen narcosis after helium-oxygen saturation. This was noted when saturated subjects entered the air space in Sealab I. It was noted that this narcosis was of a very uncomfortable variety causing headaches and nausea. To counter this, the air space was further diluted with helium, which alleviated the problem to some degree. Dr. Bond had indicated that no difficulties were encountered in decompression and that he used a 56-hour schedule, which was considerably longer than any of the planned schedules, due to the mechanical complications.

Most of the excusions from Sealab I by the participants were short trips (150-yard maximum radius) or a radius short enough so the Sealab I was always visible. Lines were laid out along the bottom in order to provide reference to the divers outside with respect to the habitat. Consequently, no navigation difficulty was encountered by the men. Furthermore, it is not felt that the method of providing location information will be necessary in future experiments.

Hookah lines to permit breathing through a hose during excursions were used during the test. The system employed had a marginal capacity even when using both pumps to supply a single diver. A constant watch was required to permit electrical tripping due to overload.

The noise level in Sealab I was mainly due to the scrubbers and dehumidifiers. Loud noises-i.e., hammering on Argus Island; the arrival of ships-could be easily hear and when the “hookah” pumps were used, the internal noise level rose considerably.

Lieutenant Commander Lanphear, the ONR project officer, has reported that instead of the 30-kw. estimate for total power (heating and lighting), a maximum demand of 10 kw. was encountered.

The major handling problems were the installation and removal of ballast near the surface, and the supporting of the large mass of the Sealab I during raising and lowering.

The umbilical cord which supplied Sealab I’s power and water (and in some cases gas and communications) was made of available material which turned out to be extrememly unwieldy in use. While no failures were noted, it was felt that is was unnecessarily fragile and would not be suitable for us in follow-up work.

The cork installation (approximately one inch thick) compressed in the helium atmosphere during descent and re-expanded fairly rapidly, while the same material on the air-space portion of Sealab I commpressed during descent but did not expand until ascent. (This is probably due to the different diffusion rates of helium and nitrogen through the cork wall cells).

Aquanaut Thompson and a surface support diver engaged in gathering marine biological samples.

The Sealab operation confirmed that helium, because it is much lighter, will penetrate materials six or seven times more readily than air. Yet, unaccountably, those wet suits which were carried down dry in Sealab I, compressed and quickly expanded after reaching bottom, thus enchancing their insulation qualities; while those worn wet by the aquanauts in their faily rapid descent outside Sealab I compressed and did not re-expand during the 12-day period. (The open-cell rubber standard issue slippers in both cases re-expanded very rapidly).

No particular problems were noted by the subjects in connection with inhaling in the high density breathing medium.

While many questions still remain to be answered and much of the data gathered in this experiment will require considerable time to analyze in detail, it has been demonstrated that the four subjects who lived at 192 feet under ambient pressure for 12 days have experienced no physiological defects considered to be serious.

Sealab has had the immediate result in the Navy of establishing under the direction of the Navy’s Special Projects Office, a well funded man-in-the-sea research effort.

Beyond Project Sealan’s intermediate and obtainable naval goal-performing underwater work anywhere on the continental shelves-lies the possibility of further exploration of the depths of the ocean abyss. Interestingly, this latter porential appears not to be limited by the enormous hydostatic pressures (approximately one psi for every 2.25 feet of depth) present at these great depths, but rather by our present scant knowledge of human responses to this hostile evironment. For example, the phenomenon of inert gas narcosis, sometimes popularly referred to as “rapture of the deep” (when applied to nitrogen narcosis), has yet to be completely understood by underwater physiologists. This effect can produce a virtual state of “drunkenness” when the subject is exposed for appreciable periods to air under high pressure. Currently, helium is used to make up the additional pressure required at depth since is does not display any appreciable narcotic effect. Possibly at some depth, however, its use will encounter the same problem.

Still another potential limitation exists in the increased breathing resistance that takes place when a diver breathes gas under pressure. This is due to the increased density of the breathing medium. As an illustration, the mixture of gas used in Sealab I increased the breathing resistance to approximately 1.6 times that of air at the surface. This condition results in some degree of additional lung fatigue which will increase with the depth.

Notwithstanding these restraints which may be imposed upon man until he is finally ready to attempt to plunge into the 1,000 meters of water and deeper which occupy over 65 per cent of this earth, we can reflect upon what the foreseeable future may hold. With knowledge gained by the Sealabs, it is conceivable , circe 1980, that

  • with provision of suitable mobile and fixed habitations, man will be able to live and work for months on the ocean bottom at depths heretofore thought impossible. It could become accepted practice for such men to live in ocean floor shelters emerging to the ocean outside to perform various naval operations, oil drilling and mining tasks, fish farming, and sea crop harvesting.
  • ships could be repaired and reconditioned without removing them from the water.
  • salvage and rescue techniques now considered impossible could become possible.
  • a vast, new spectrum of ocean engineering and naval operations would become possible.

Lieutenant Commander Groves served on active duty from 1943 until 1946. Recalled during the Korean conflict, he served in engineering billets until his release to inactive duty in 1954. He has been a member of the Division of Engineering and Research staff of the National Academy of Sciences-National Research Council since December 1961.This article is an outgrowth of his Naval Reserve affiliation with the Research Program of the Office of Naval research, which was charged with the execution of the Sealab program.

 
 
 
  • anon

    what is decompression

 
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