U.S. Navy Diving and Aviation Safety

Blood pressure is not the only silent medical killer. Hypoxia is also, and unlike chronically elevated blood pressure, it cripples within minutes, or seconds.

Hypoxia, a condition defined by lower than normal inspired oxygen levels, has killed divers during rebreather malfunctions, and it has killed pilots and passengers, as in the 1999 case of loss of cabin pressure in a Lear Jet that killed professional golfer Payne Stewart and his entourage and aircrew. Based on Air Traffic Control transcripts, that fatal decompression occurred somewhere between an altitude of 23,000 feet and 36,500 ft.

In most aircraft hypoxia incidents, onset is rapid, and no publically releasable record is left behind. The following recording is an exception, an audio recording of an hypoxia emergency during a Kalitta Air cargo flight.

Due to the seriousness of hypoxia in flight, military aircrew have to take recurrent hypoxia recognition training, often in a hypobaric (low pressure) chamber.

As the following video shows, hypoxia has the potential for quickly disabling you in the case of an airliner cabin depressurization.

Aircrew who must repeatedly take hypoxia recognition training are aware that such training comes with some element of risk. Rapid exposure to high altitude can produce painful and potentially dangerous decompression sickness (DCS) due to the formation of bubbles within the body’s blood vessels.

In a seminal Navy Experimental Diving Unit (NEDU) report published in 1991, LCDR Bruce Slobodnik, LCDR Marie Wallick and LCDR Jim Chimiak, M.D. noted that the incidence of decompression sickness in altitude chamber runs from 1986 through 1989 was 0.16%, including both aviation physiology trainees and medical attendants at the Naval Aerospace Medical Institute. Navy-wide the DCS incidence “for all students participating in aviation physiology training for 1988 was 0.15%”. If you were one of the 1 and a half students out of a thousand being treated for painful decompression sickness, you would treasure a way to receive the same hypoxia recognition training without risk of DCS.

With that in mind, and being aware of some preliminary studies (1-3), NEDU researchers performed a double blind study on twelve naïve subjects. A double-blind experimental design, where neither subject nor investigator knows which gas mixture is being provided for the test, is important in medical research to minimize investigator and subject bias. Slobodnik was a designated Naval Aerospace Physiologist, Wallick was a Navy Research Psychologist, and Chimiak was a Research Medical Officer. (Chimiak is currently the Medical Director at Divers Alert Network.)

Three hypoxic gas mixtures were tested (6.2% O2, 7.0% and 7.85% O2) for a planned total of 36 exposures. (Only 35 were completed due to non-test related problems in one subject.) Not surprisingly, average subject performance in a muscle-eye coordination test (two-dimensional compensatory tracking test) declined at the lower oxygen concentrations. [At the time of the testing (1990), the tracking test was a candidate for the Unified Triservice Cognitive Performance Assessment Battery (UTC-PAB)].

As a result of this 1990-1991 testing (4), NEDU proved a way of repeatedly inducing hypoxia without a vacuum chamber, and without the risk of DCS.

The Navy Aerospace Medical Research Laboratory built on that foundational research to build a device that safely produces hypoxia recognition training for aircrew. That device, a Reduced Oxygen Breathing Device is shown in this Navy photo.

070216-N-6247M-009 Whidbey Island, Wash. (Feb 16, 2007) Ð Lt. Cmdr. James McAllister, from San Diego, Calif. sits in the simulator during a test flight using the new Reduced Oxygen Breathing Device (ROBD). The ROBD is a portable device that delivers a mixture of air, nitrogen and oxygen to aircrew, simulating any desired altitude. Combined with a flight simulator the ultimate effect replicates an altitude induced hypoxia event. McAllister is the Director of the Aviation Survival Training Center at Whidbey Island. U.S. Navy photo by Mass Communication Specialist 1st Class Bruce McVicar (RELEASED)
Whidbey Island, Wash. (Feb 16, 2007) Lt. Cmdr. James McAllister, from San Diego, Calif. sits in the simulator during a test flight using the Reduced Oxygen Breathing Device (ROBD). The ROBD is a portable device that delivers a mixture of air, nitrogen and oxygen to aircrew, simulating any desired altitude. Combined with a flight simulator the ultimate effect replicates an altitude induced hypoxia event. McAllister is the Director of the Aviation Survival Training Center at Whidbey Island. U.S. Navy photo by Mass Communication Specialist 1st Class Bruce McVicar.

Although NEDU is best known for its pioneering work in deep sea and combat diving, it continues to provide support for the Air Force, Army and Marines in both altitude studies of life-saving equipment, and aircrew life support systems. Remarkably, the deepest diving complex in the world, certified for human occupancy, also has one of the highest altitude capabilities. It was certified to an altitude of 150,000 feet, and gets tested on occasion to altitudes near 100,000 feet. At 100,000 feet, there is only 1% of the oxygen available at sea level. Exposure to that altitude without a pressure suit and helmet would lead to almost instantaneous unconsciousness.

OSF FL 900
A test run to over 90,000 feet simulated altitude.

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  1. Herron DM. Hypobaric training of flight personnel without compromising quality of life. AGARD Conference Proceedings No. 396, p. 47-1-47-7.
  2. Collins WE, Mertens HW. Age, alcohol, and simulated altitude: effects on performance and Breathalyzer scores. Aviat. Space Environ Med, 1988; 59:1026-33.
  3. Baumgardner FW, Ernsting J, Holden R, Storm WF. Responses to hypoxia imposed by two methods. Preprints of the 1980 Annual Scientific Meeting of the Aerospace Medical Association, Anaheim, CA, p: 123.
  4. Slobodnik B, Wallick MT, Chimiak, JM. Effectiveness of oxygen-nitrogen gas mixtures in inducing hypoxia at 1 ATA. Navy Experimental Diving Unit Technical Report 04-91, June 1981.

 

Remote Viewing – Stretching the Limits of Science in Fiction

puthoff_lg
Laser physicist Harold E. Puthoff.

I once met the Father of the U.S Remote Viewing program, unawares.

A decade ago, at the request of a Navy engineer who ended up being a character in my novel Middle Waters, I invited Dr. Harold E. Puthoff into the Navy Experimental Diving Unit to give a talk on advanced physics. He had attracted a small but highly educated and attentive crowd which, like me, had no idea that the speaker had once led the CIA in the development of its top secret Remote Viewing program.

Of late, Puthoff’s energies have been directed towards the theoretical “engineering of space time” to provide space propulsion, a warp drive if you will. Although strange by conventional physics standards, similar avant-garde notions are receiving traction in innovative space propulsion engines such as NASA’s EMdrive.

Puthoff is the Director of the Institute of Advanced Studies at Austin, in Texas, but before that, and more germane to this discussion, Puthoff was a laser physicist at the Stanford Research Institute. It was there that the CIA chose him to lead a newly created Remote Viewing program, designed to enable the U.S. to maintain some degree of competiveness with Russia’s cold war psychic spying program.

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6800 feet down in the Desoto Canyon

Psychic spying was purportedly the method used by the two superpowers to visualize things from a distance; not from a satellite, but from what some call the highly developed powers of the mind’s eye. If we believe what we read on the subject, Remote Viewing was eventually dropped from the US psychic arsenal not because it had no successes, but because it was not as reliable as signal intelligence (SIGINT), satellite imagery, and spies on the ground. But, it has been argued, it might be ideal in locations where you can’t put spies on the ground, such as the dark side of the moon, or the deep sea .

Serendipitously, as I started writing this blog post, Newsweek published a review of the Remote Viewing efforts of Puthoff and others in a November 2015 issue. The article seemed fairly inclusive, at least more so than other articles on Remote Viewing I’ve seen, but the Newsweek author was not particularly charitable towards Puthoff. Strangely, the strength and veracity of Puthoff’s science was reportedly criticized by two New Zealand psychologists who, as the Newsweek author quoted, had a “premonition” about Puthoff.

“Psychologists” and “premonitions” are not words commonly heard in the assessment of science conducted by laser physicists, especially those employed by the CIA. The CIA is not stupid, and neither are laser physicists from Stanford.

To the extent that I am able to judge a man by meeting him in person and hearing him talk about physics, I would have to agree with Puthoff’s decision to ignore his ill-trained detractors. Every scientist I know has had detractors, and as often as not those detractors have lesser credentials. Nevertheless, I have the good sense to not debate the efficacy of remote viewing. I don’t know enough about it to hold an informed opinion. However, there seems to be some evidence that it worked occasionally, and for a science fiction writer that is all that is needed.

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Nuclear physicist Enrico Fermi.

As my curiosity became piqued by the discovery of the true identity of my guest speaker at NEDU, and as I learned what he had done for the U.S. during the Cold War, I thought of another great physicist, Enrico Fermi, one of the fathers of the atomic bomb. In the midst of a luncheon conversation with Edward Teller, Fermi once famously asked, “Where are they?” The “they” he was referring to, were extraterrestrial aliens.

What became known as Fermi’s Paradox went something like this: with all the billions of stars with planets in our galactic neighborhood, statistically there should be alien civilizations everywhere. But we don’t see them. Why not? “Where are they?”

In most scientists’ opinions, it would be absurdly arrogant for us to believe we are the only intelligent life form in the entire universe. And so ETs must be out there, somewhere. And if there, perhaps here, on our planet, at least occasionally. And that is all the premise you need for a realistic, contemporary science fiction thriller.

But then there is that pesky Fermi Paradox. Why don’t we see them?

Well, they could indeed be here, checking us out by remote viewing, all the while remaining safely hidden from sight. After all, as one highly intelligent Frog once said, humans are a “dangerous species” fictionally speaking of course.

That “hidden alien” scenario may be improbable, but it’s plausible, if you first suspend a little disbelief. If we can gather intelligence while hiding, then certainly they can, assuming they are more advanced than humans. A technological and mental advantage seems likely if they are space travelers, which they almost have to be within the science fiction genre. Arguably, fictional ETs may have long ago engineered space-time, which could prove mighty convenient for tooling around the galactic neighborhood.

So, if in the development of a fictional story we assume that ETs can remote view, the next question would be, why? Is mankind really that dangerous?

Well, I don’t intend for this post to be a spoiler for Middle Waters, but I will say that the reasons revealed in the novel for why ETs might want to remote view, are not based on fear of humans, but are based on sound science. From that science, combined with a chance meeting with Hal Puthoff, the basic premise of a science fiction thriller was born.

So, to correct what some of my readers have thought, I did not invent the concept of “remote viewing”. It is not fictional; it is real, and was invented and used by far smarter people than myself, or even that clever protagonist, Jason Parker.

 

 

Authorized for Cold Water Service: What Divers Should Know About Extreme Cold

The following is reprinted from my article published in ECO Magazine, March 2015.  It was published in its current format as an ECO Editorial Focus by TSC Media. Thank-you Mr. Greg Leatherman for making it available for reprinting.ECO Magazine

It is the highpoint of your career as an environmentally minded marine biologist. The National Science Foundation has provided a generous grant for your photographic mission to the waters 100 ft below the Ross Ice Shelf, Antarctica. Now you’re on an important mission, searching for biological markers of climate change.

Picture1
Under Antarctic Ice, photo by Dr. Martin Sayer.

Above you lies nothing but a seemingly endless ceiling of impenetrable ice, 10 ft thick. Having spent the last several minutes concentrating on your photography, you look up and notice you’ve strayed further from safety than you’d wanted. The strobe light marking the hole drilled in the ice where you’ll exit the freezing water is a long swim away. And, unfortunately, your fellow scientist “buddy” diver has slipped off somewhere behind you, intent on her own research needs.

You’re diving SCUBA with two independent SCUBA regulators, but in the frigid cold of the literally icy waters, you know that ice could be accumulating within the regulator in your mouth. At the same time, a small tornado of sub-zero air expands chaotically within the high-pressure regulator attached to the single SCUBA bottle on your back—and that icy torrent is increasingly sucking the safety margins right out of your regulator. You are powerless to realize this danger or to do anything about it.

At any moment, your regulator could suddenly and unexpectedly free flow, tumultuously dumping the precious and highly limited supply of gas contained in the aluminum pressure cylinder on your back. You’re equipped and trained in the emergency procedure of shutting off the offending regulator and switching to your backup regulator, but this could also fail. It’s happened before. 

As you try to determine your buddy’s position, you’re feeling very lonely. You realize the high point of your career could rapidly become the low point of your career—and an end to your very being. Picture046

The preceding is not merely a writer’s dramatization. It is real, and the situation could prove deadly—as it has in far less interesting and auspicious locations. Regulator free flow and limited gas supplies famously claimed three professional divers’ lives in one location within a span of one month.

There is a risk to diving in extreme environments. However, the U.S. Navy has found that the risk is poorly understood, even by themselves—the professionals. If you check the Internet SCUBA boards, you constantly come across divers asking for opinions about cold-watersafe regulators. Undoubtedly, recent fatalities have made amateur divers a little nervous—and for good reason.

Internet bulletin boards are not the place to get accurate information about life support safety in frigid water. Unfortunately, the Navy found that manufacturers are also an unreliable source. Of course, the manufacturers want to be fully informed and to protect their customers, but the fact remains that manufacturers test to a European cold-water standard, EN 250. By passing those tests, manufacturers receive a “CE” stamp that is pressed into the hard metal of the regulator. That stamp means the regulator has received European approval for coldwater service.

As a number of manufacturers have expensively learned, passing the EN 250 testing standard is not the same as passing the more rigorous U.S. Navy standard, which was recently revised, making it even more rigorous by using higher gas supply pressures and testing in fresh as well as salt water. Freshwater diving in the Navy is rare—but depending on the brand and model of regulator in use, it can prove lethal.

The unadorned truth is that the large majority of manufacturers do not know how to make a consistently good Performing cold-water regulator. Perhaps the reason is because the type of equipment required to test to the U.S. Navy standard is very expensive and has, not to date, been legislated. Simply, it is not a requirement.

Some manufacturers are their own worst enemy; they cannot resist tinkering with even their most successful and rugged products. This writer is speculating here, but the constant manufacturing changes appear to be driven by either market pressures (bringing out something “new” to the trade show floor) or due to manufacturing economy (i.e., cost savings). The situation is so bad that even regulators that once passed U.S. Navy scrutiny are in some cases being changed almost as soon as they reach the “Authorized for Military Use” list. The military is struggling to keep up with the constant flux in the market place, which puts the civilian diver in a very difficult position. How can they—or you—know what gear to take on an environmentally extreme dive?

My advice to my family, almost all of whom are divers, is to watch what the Navy is putting on their authorized for cold-water service list. The regulators that show up on that list (and they are small in number) have passed the most rigorous testing in the world.

Through hundreds of hours of testing, in the most extreme conditions possible, the Navy has learned what all SCUBA divers should know:

• Even the coldest water (28°F; -2°C) is warm compared to the temperature of expanding air coming from a first stage regulator to the diver. There is a law of physics that says when compressed air contained in a SCUBA bottle is expanded by reducing it to a lower pressure, air temperature drops considerably. It’s the thermal consequence of adiabatic (rapid) expansion.

• Gas expansion does not have to be adiabatic. Isothermal (no temperature change) expansion is a process where the expansion is slow enough and heat entry into the gas from an outside source is fast enough that the expanded gas temperature does not drop.

• The best regulators are designed to take advantage of the heat available in ice water. The most critical place for that to happen is in the first stage where the greatest pressure drop occurs (from say 3,000 psi or higher to 135 psi above ambient water pressure (i.e., depth). They do that by maximizing heat transfer into the internals of the regulator.

• First stage regulators fail in two ways. The most common is that the first stage (which controls the largest pressure drop) begins to lose control of the pressure being supplied to the second stage regulator, the part that goes into a diver’s mouth. As that pressure climbs, the second stage eventually can’t hold it back any longer and a free flow ensues.

• The second failure mode is rare, but extremely problematic. Gas flow may stop suddenly and completely, so that backup regulator had better be handy.

• Second stage regulators are the most likely SCUBA components to fail in cold water due to internal ice accumulation.

• Free flows may start with a trickle, slowly accelerating to a torrent, or the regulator may instantly and unexpectedly erupt like a geyser of air. Once the uncontrolled, and often unstoppable free flow starts, it is self-perpetuating and can dump an entire cylinder of air within a few minutes through the second stage regulator.

• A warm-water regulator free flow is typically breathable; getting the air you need to ascend or to correct the problem is not difficult. In a cold-water-induced free flow, the geyser may be so cold as to make you feel like you’re breathing liquid nitrogen and so forceful as to be a safety concern. Staying relaxed under those conditions is difficult, but necessary.

• Water in non-polar regions can easily range between and 34°F to 38°F; at those temperatures, gas entering the second stage regulator can be at sub-freezing temperatures. European standard organizations classify ~10°C (50°F) as the cold/non-cold boundary. The Navy has found in the modern, high-flow regulators tested to date that 42°F is the water temperature where second stage inlet temperature is unlikely to dip below freezing.

• The small heat exchangers most manufacturers place just upstream of the second stage is ineffective In extreme conditions. They quickly ice over, insulating that portion of the regulator from the relative warmth of the surrounding water. Heat Ex Regulator

• Regulator “bells and whistles” are an unknown and can be problematic. Second stage regulators with multiple adjustments can do unpredictable things to heat transfer as the diver manipulates his controls. The last thing a cold-water diver should want is to make it easier to get more gas. High gas flows mean higher temperature drops and greater risk of free flow.

• Only manufacturer-certified technicians should touch your regulator if you’re going into risky waters. The technician at your local dive shop may or may not have current and valid technician training on your particular life support system. Don’t bet your life on it— ask to see the paperwork.

• Follow Navy and Smithsonian* guidance on handling and rinsing procedures for regulators in frigid waters. A single breath taken above the surface could freeze a regulator before you get your first breath underwater.

U. S. Navy reports on tested regulators are restricted. However, the list of those regulators passing all phases of Navy testing is available online. If your regulator, in the exact model as tested, is not on that list, do yourself a favor and don’t dive in frigid waters.

 

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The original Editorial Focus article is found in the digital version of the March ECO magazine here, on pages 20-25.

 

Don’t Dive Cold When You Don’t Have To

 

San Diego Center of Excellence in Diving

Clarke JR1, Moon RE2, Chimiak JM3, Stinton R4, Van Hoesen KB5, and Lang MA5,6.

1 US Navy Experimental Diving Unit, Panama City, Florida
2 Duke University, Durham, North Carolina
3 Divers Alert Network, Durham, North Carolina
4 Diving Unlimited International, Inc., San Diego, California
5 UC San Diego – Emergency Medicine, San Diego, California
6 OxyHeal Health Group, National City, California

 Introduction

The San Diego Center of Excellence in Diving at UC San Diego aims to help divers be effective consumers of scientific information through its “Healthy Divers in Healthy Oceans” mission. In this monograph we explore a research report from the Navy Experimental Diving Unit (NEDU) that is leading some divers to think they should be cold if they want to reduce decompression risk. That is a misinterpretation of the report, and may be causing divers to miss some of the joy of diving. There is no substitute for comfort and safety on a dive.

Background

In 2007 NEDU published their often-cited report “The Influence of Thermal Exposure on Diver Susceptibility to Decompression Sickness” (Gerth et al., 2007). The authors, Drs. Wayne Gerth, Victor Ruterbusch, and Ed Long were questioning the conventional wisdom that cold at depth increases the risk of decompression illness. After conducting a very carefully designed experiment, they were shocked to find that exactly the opposite was true. Some degree of cooling was beneficial, as long as the diver was warm during ascent.

Discussion and Implications

There are some important caveats for the non-Navy diver to consider. First of all, it was anticipated that a diver would have a system for carefully controlling their temperature during the separate phases of bottom time and decompression. Most non-Navy divers do not have that sort of surface support.

Secondly, the “cold” water in the NEDU study was 80 °F (27 °C). For most of us, 80 °F (27 °C) is an ideal swimming pool temperature, not exactly what you are going to find in non-tropical oceans and lakes. The warm water was 97 °F (36 °C), also a temperature not likely to be available to recreational and technical divers.

When testing the effect of anything on decompression results, the Navy uses their extensive mathematical expertise to select the one dive profile that is, in their estimation, the most likely to identify a difference in decompression risk, if that difference in risk exists. In this case the profile selected was a 120 fsw (37 msw) dive with 25 to 70 min bottom time, decompressed on a US Navy Standard Air table for 120 fsw (37 msw) and 70 min bottom time. That table prescribes 91 minutes of decompression divided thusly: 30 fsw/9 min (9msw/9 min), 20 fsw/23 min (6 msw/23 min), 10 fsw/55 min (3 msw/55 min).

A total of 400 carefully controlled dives were conducted yielding 21 diagnosed cases of decompression sickness. Overwhelmingly, the lowest risk of decompression was found when divers were kept warm during decompression. The effects of a 9 °C increase in water temperature during decompression was comparable to the effects of halving bottom time.

That is of course a remarkable result, apparently remarkable enough to cause civilian divers to alter their behavior when performing decompression dives. However, before you decide to chill yourself on the bottom or increase your risk of becoming hypothermic, consider these facts.

  1. Do you have a way of keeping yourself warm, for instance with a hot water suit, during decompression? If not, the study results do not apply to you.
  2. Of the many possible decompression schedules, the Navy tested only one schedule, the one considered to be the best for demonstrating a thermal influence on decompression risk. Although it seems reasonable that this result could be extrapolated to other dive profiles, such extrapolation is always risky. It may simply not hold for the particular dive you plan to make, especially if that dive is deeper and longer than tested.
  3. Most commercial decompression computers do not adhere to the U.S. Navy Air Tables; few recreational dives are square profiles. Furthermore, additional conservatism is usually added to commercial algorithms. NEDU is not able to test the effects of diver skin temperature on all proprietary decompression tables, nor should they. That is not their mission.
  4. The scientific method requires research to be replicated before test results can be proven or generalized. However, due to the labor and expense involved in the NEDU dive series, it seems unlikely that any experiments that would determine the relevance of these results to recreational or technical diving will ever be performed. As such, it may raise as many questions as it answers. For instance, the original question remains; if you become chilled on a dive, how does that affect your overall risk of decompression illness compared to remaining comfortably warm? Unfortunately, that question may never be answered fully.
  5. Thermoneutral temperatures for swim suited divers are reported to be 93 °F to 97 °F (34 to 36 °C) for divers at rest and 90 °F (32 °C) during light to moderate work (Sterba, 1993). So a skin temperature of 80 °F (27 °C) is indeed cold for long duration dives. If your skin temperature is less than 80 °F (27 °C), then you are venturing into the unknown; NEDU’s results may not apply.In summary, beer and some types of wine are best chilled. Arguably, divers are not.

Acknowledgments

Support for the San Diego Center of Excellence in Diving is provided by founding partners UC San Diego Health Sciences, UC San Diego Scripps Institution of Oceanography, OxyHeal Health Group, Divers Alert Network, Diving Unlimited International, Inc. and Scubapro.

References

Gerth WA, Ruterbusch VL, Long ET. The Influence of Thermal Exposure on Diver Susceptibility to Decompression Sickness. NEDU Technical Report 06-07, November 2007.

Sterba JA. Thermal Problems: Prevention and Treatment, in P.B. Bennett and D.H. Elliot, eds., The Physiology and Medicine of Diving, 4th ed. (London: Saunders, 1993), pp. 301-341.

Keep Your Powder Dry, Rebreather Divers

Compared to decompression computers, digital oxygen control, and fuel cell oxygen sensors, carbon dioxide absorbent is low tech and not at all sexy. Perhaps because it is low in diver interest, it is poorly understood. In rebreather diving, a lack of knowledge is dangerous.

The U.S. Navy Experimental Diving Unit (NEDU) is intimately familiar with sodalime, the crystalline carbon dioxide absorbent used in a wide variety of self-contained breathing apparatus for both diving and land use. NEDU routinely tests sodalime during accident investigations, during CO2 scrubber canister duration determinations, or during various research and development tasks. They have developed computer models of scrubber canister kinetics, and patented and licensed technology for use in determining how long a scrubber will last in diving and land applications.

The types of sodalime in NEDU’s experimental inventory are:  Sodasorb_rotate

  1. Sofnolime 408 Mesh NI L Grade
  2. Sofnolime 812 Mesh NI D Grade
  3. HP Sodasorb (4/8 Reg HP)
  4. Dragersorb 400
  5. Limepak
  6. Micropore

Absorbent undergoes a battery of quality tests at NEDU, most of them in accordance with NATO standardized testing procedures (STANAG 1411). One test is of the distribution of sodalime granule sizes, and another tests the softness or friability of the granules. One test checks the moisture content of the sample, and another tests the CO2 absorption ability of a small sample of absorbent.

From time to time, absorbent lot samples fail one or more of these tests. One failure of granule size distribution was caused by changes in production procedures. “Worms” of absorbent rather than granules of absorbent started showing up in sodalime pails. In another case, absorbent was found to have substandard absorption activity, and in yet another, the material was too soft. Too soft or friable material  can allow granules to breakdown, turning into dust.

This would not be a major problem, except that a diver or miner has to breathe through his granular absorbent bed, and dust clogs that bed, making breathing difficult. In the extreme, labored breathing from unusually high dust loading can result in unconsciousness.

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Sample bags of sodalime removed from absorbent buckets, awaiting testing.

What does the above have to do with this post’s title?

Supposedly, the maxim “Trust in God, but keep your powder dry” was uttered by Oliver Cromwell, but  first appeared in 1834 in the poem “Oliver’s Advice” by William Blacker with the words “Put your trust in God, my boys, and keep your powder dry!” If indeed Cromwell did say it, then it dates from the 1600’s.

A much more modern interpretation, appropriate for rebreather divers, is as follows: buckets of sodalime with a larger than usual layer of dust at the bottom (due to the mechanical breakdown of absorbent granules during shipment), should be kept dry. In other words, don’t dive it!

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Micropore rolled carbon dioxide absorbent on the right, granular absorbent on the left.

Presumably this is not an issue with Micropore ExtendAir CO2 absorbent since it’s basically sodalime powder suspended on a plastic medium. The diver breathes through fixed channels in the ExtendAir cartridge, not through the powder.

Considering the relatively high cost of granular sodalime, a diver might be very reluctant to discard an entire bucket of absorbent with a non-quantifiable amount of dusting. They certainly will not be performing sieve tests for granule size distributions like NEDU, however one simple solution to a suspected dusting problem might be to sieve the material before diving it. The only requirement would be that only the dust should be discarded, not whole granules. In other words, your sieve must have a  fine mesh.

In NEDU’s experience, quality control issues are not necessarily a problem with manufacturing. Where and how sodalime is stored can apparently have an appreciable effect on sodalime hardness.  The same lot of sodalime stored in two different but close proximity locations has been found to differ markedly in its friability. Exactly why that should be, is presently unknown.

Regardless of whether the subject is sexy or not, a wise rebreather diver will seek all the knowledge available for his “sorb”, as it’s sometime called. After all, the coolest decompression computer in the world will do you no good at all if you’re unconscious on the bottom because you tried to outlast your CO2 absorbent.

 

 

 

 

 

 

How Much is Too Much? (Carbon Dioxide – The Diver’s Nemesis)

The amount of carbon dioxide (CO2) that can be safely inhaled by rebreather divers is a continuing point of conjecture, and vigorous argument. Unfortunately, the U.S. Navy  Experimental Diving Unit has confused that issue, until recently.

A non-diver might wonder why a diver should inhale any CO2. After all, the air we breathe contains only a small fraction of CO2 (0.039%). A rebreather is best known for emitting no bubbles, or at most very few bubbles depending on the type of rebreather. It does that by recirculating the diver’s breath, adding oxygen to make up for oxygen consumed by the diver, and absorbing the carbon dioxide produced by the diver. The CO2 scrubber canister is vital to keeping the diver alive. As pointed out in the first post in this series, carbon dioxide is toxic; it can kill.

A CO2 scrubber  keeps the recirculating CO2 levels low by chemically absorbing exhaled CO2. However, the scrubber has a finite lifetime – it can only absorb so much CO2. Once its capacity has been exceeded, CO passing through the canister accumulates exponentially as the diver continues to produce CO2 from his respiration.

The question rebreather divers want answered is, “How much of that bypassed CO2 can I tolerate?” As we’ve discussed in previous posts, 30% CO2 can incapacitate you within a few breaths. I can personally verify that if you’re exercising you may not notice the effect 7% CO2 has on you, until you try to do something requiring coordination. I’d equate it to the effect of drinking too many beers. There is little controversy about CO2 levels of 5-7% being bad for a diver.

For levels below 5-7% CO2, the U.S. Navy has not been real clear. For instance, 2% CO2 is the maximum CO2 allowed in diving helmets. If CO2 were to climb higher the diver would most likely feel a need to ventilate the helmet by briefly turning up the fresh gas supply to clear CO2.

Since at least 1981, NEDU has defined the scrubber canister breakthrough point in rebreathers as 0.5% CO2. That means that at some point, which varies with CO2 injection rate, ventilation rate, water temperature, and grain size of CO2 absorbent, CO2 begins leaking past the canister, not being fully absorbed during its passage through the canister. Once that leakage starts, the amount of CO2 entering the diver’s inspired breath rises at an ever increasing rate unless work rate or other variables change. By the time the CO2 leaving the canister has reached 0.5%, the canister has unequivocally “broken through”.

I pointed out in my last post that even 0% inspired CO2 may be too much for some divers when they are facing resistance to breathing. And all rebreathers are more difficult to breathe than other types of underwater breathing apparatus because the diver has to force his breath through the rig’s scrubber canister and associated hoses. The deeper the dive the denser the breathing gas and the worse breathing resistance becomes.

In free-flow diving helmets like the old MK 5, and the short-lived MK 12, the diver did not breathe through hoses and scrubber canisters. But those helmets had a high dead space and to keep helmet CO2 at tolerable levels a fresh gas flow of 6 actual cubic feet per minute (acfm; 170 liters per minute) was required. The U.S. Navy allowed up to 2% CO2 in the helmet because 1) the helmets did not have a high work of breathing and 2) due to simple physics the helmet CO2 couldn’t be kept very low.

For rebreathers, none of the above apply. A high breathing resistance is inevitable, at least compared to free-flow helmets, and once CO2 starts rising there is nothing you can do to decrease it again, short of stopping work.

In 2000, NEDU’s M. Knafelc published a literature review espousing that the same limit for inspired CO2 which applies in helmets could be used in rebreathers. Nevertheless, in 2010 NEDU’s D. Warkander and B. Shykoff clearly demonstrated that in the face of rising inspired CO2 concentrations work performance is reduced, and blood levels of CO2 rise, in some cases to dangerous levels. More recent work by the Warkander and Shykoff duo have extended those studies into submersion, however those reports are not yet publicly available.

As a result of both physiological theory and confirmatory data in young, physically-fit experimental divers, NEDU has not relaxed the existing definitions of scrubber canister breakthrough, 0.5% PCO2. Furthermore NEDU will adhere to the current practice of using statistical prediction methods to define published canister durations, methods which are designed to keep the odds of a diver’s rebreather canister “breaking through” to no more than 2.5%, comparable to the odds of decompression sickness following Navy multi-level dive tables. Details of this procedure will be explained in later postings.

 

Children of the Middle Waters

Children of the Middle Waters (working title) is a science fiction/thriller that has been completed and is being submitted today for consideration by Tom Doherty Associates, New York. My friend and mentor, the writer Max McCoy, has provided literary criticism and encouragement for the manuscript. Max, who works primarily in the Western genre, wrote a diving-related thriller called The Moon Pool, which happens to involve in its closing chapter the Navy Experimental Diving Unit, and someone a lot like me.

Below is a blurb briefly describing Children of the Middle Waters.

In the deep-sea canyons and trenches of the Earth lie thousands of alien spacecraft and millions of their inhabitants who have to leave soon or risk being stranded forever, or being destroyed. Due to their physiology they have been unable to directly contact humans, but they are adroit at mental contact and remote viewing, when it suits them.

They need the help of two humans to assure their safe escape, an experienced Navy scientist and a beguiling graduate student.  But introductions through mental means are slow and suspect, as you might imagine.

The U.S. government is well aware of this deep sea civilization, and is desirous of the weapons the visitors possess, which puts the two unsuspecting scientists in the middle of a conflict between powerful
military forces and powerful intergalactic forces. Things could get messy.

Even worse, jealous friends turn on the unlikely duo and put their lives at risk.

Children combines two separate Native American beliefs and legends with current events. It is a complex thriller with science fact and science fiction mixed in with military action and government intrigue. Also revealed are romantic possibilities that far exceed the capabilities of the mundane, everyday world.

Early American Indian beliefs create an ending for this story that no one could anticipate. It is an ending that causes the protagonist to realize everything he has held dear is wrong, in one way or another. At the same time he discovers a reality that is the greatest blessing that man can receive.

 

A Look Inside Rebreather Scrubber Canisters, Part 1

If you’re diving a rebreather (closed-circuit breathing apparatus to be exact), then you know the scrubber removes carbon dioxide from your recirculated breath. Without the scrubber working, you’d go unconscious from carbon dioxide intoxication within a very few minutes of starting the dive.

But do you really know what’s going on inside that scrubber canister?

A stochastic computer simulation developed by the author gives as realistic a glimpse inside as we can get.

Loose granular and rolled sodalime. Click to enlarge.

Carbon dioxide scrubber canisters usually contain a chemical mixture called sodalime that chemically reacts with carbon dioxide in a diver’s expired breath. That material may be in granular form, or in a preformed roll. Sodalime is a mixture of calcium hydroxide and sodium hydroxide, which when it reacts by absorbing carbon dioxide is converted into calcium carbonate (CaCO3, calcite), a major constituent of limestone.

The overall chemical reaction can be simplified to:

CO2 + Ca(OH)2 → CaCO3 + H2O + heat

In the following sequence of images we see a rectangular prism shaped scrubber canister arranged axially such that the diver’s expired breath enters the section from the left, passing completely through the canister section before exiting to the right. A portion of the canister was cut away digitally after the simulation was run to allow visualization of temperatures within the canister interior.

Beginning of the simulation. Click to enlarge.

Initially, the canister is at room temperature, and then is immersed in cold water as the diver begins his dive. Temperature is color coded: the coldest temperature is black, and increasing warmth is portrayed in an intuitive fashion from purple to red to yellow, and finally white, being the highest temperature.

In the first image, CO2 has just started reacting with the sodalime at the entrance to the canister section, with a slight heating resulting. Thermal conduction is cooling the exterior surface of the canister, but most of the inside still remains at room temperature.

In the second image, the reaction front has clearly formed, and the hottest portion of the canister has begun moving downstream. Convection carries heat rapidly downstream to heat the diver’s inspired breath, and is seen to offset canister cooling due to conduction from the surrounding cold water.

Click to enlarge

In the image to the left, the heating front is fully developed, and residual heat has spread almost completely throughout the downstream portion of the canister.

In the next image, to the right, the front is beginning to weaken in intensity.

 

 

 

Finally (lower left figure), the thermal heating in the reaction front, indicative of CO2 absorption effectiveness, is fading out, and the cooling of the canister from the surrounding cold water is beginning to win the tug of war between heat generation and conductive cooling.

At that point in time, the canister is spent, and essentially all of the exhaled CO2 is passing right through the canister without being absorbed. If the diver had not ended his dive before his canister reached this point, he would be at great risk of passing out due to CO2 accumulation.

The last figure (lower right) shows temperature readings at various locations, and at various times (reps) throughout the simulation run. The orange and brown traces marked “temp” are measured temperatures from locations near the entrance to the canister. They rise abruptly as the absorption reactions start, and fall quickly as the reaction front moves past them, downstream.

Click to enlarge

The curves that remain elevated longer represent the average exhaled gas temperature, and the average temperature within the absorbent bed. After reaching a peak, the average bed temperature steadily drops as cold gas from the inlet (exhaled) gas chills the portion of the bed behind the reaction front. Exhaled gas temperature, on the other hand, climbs more slowly, but remains more stable until the bed becomes depleted of absorbent activity.

The monitoring of absorbent canister temperature changes is what makes the rebreather scrubber canister monitors used in the Inspiration and Sentinel rebreathers possible. The Sentinel technology is licensed from the U.S. Navy Experimental Diving Unit.

In the next posting, we’ll see the surprising way that cold canisters fill up with calcium carbonate.

 

 

 

 

 

 

 

 

 

The following is a high definition video of the computer simulation of heat generation and loss in a short cylindrical canister. For best effect go to full screen and 1080p mode.

 

 

Further details about the computer simulation involved in the production of these images and video can be found in the paper “Computer Modeling of the Kinetics of CO2 Absorption in Rebreather Scrubber Canisters”, in MTS/IEEE OCEANS 2001 Conference Proceedings, published by the Marine Technology Society; Institute of Electrical and Electronics Engineers; Oceanic Engineering Society (U.S.); IEEE Xplore (Online service).

Diving Accident Investigation

Diving helmets waiting for accident investigations. Click for a larger image.

Compared to aircraft accident investigations, diving accident investigations are often ad hoc in nature, poorly conceived and poorly funded. Nevertheless, these investigations are just as important for the safety of the diving public as are similar investigations for the flying public. Unfortunately, no national regulations presently address how investigations of diving accidents should be conducted: volunteer investigators have no legal status for extracting information about an accident, and they have no legally binding protection from litigation based on the conduct of their investigation or on its results. That is, no business case can be made for conducting diving accident investigations, in spite of the moral authority for conducting them.

With the conviction that this untenable situation must eventually change, this presentation will describe one approach to diving accident investigations with particular emphasis on rebreathers and will draw some comparisons to aviation accident investigations by the National Transportation Safety Board (NTSB).

Aircraft accident investigations

The "black box" containing data recorded just prior to, and during, a commercial aircraft accident.

Pilots know that if they are involved in a fatal crash, the NTSB will investigate the accident by examining in excruciating detail everything those pilots did for hours, perhaps even days or weeks, leading up to that accident. It will investigate how often they called flight service to check on the weather. The NTSB will go through those pilots’ personal logbooks to check on their currency and proficiency, and it will check Federal Aviation Administration (FAA) records for a history of violations. NTSB investigators will also examine an aircraft’s logbooks to scrutinize its maintenance records. They will play back voice and radar data, and if a data recorder is available, they will analyze its contents.

Then they get personal. The NTSB and its FAA counterparts will talk to mechanics, surviving passengers, and friends to ask questions such as, “What were the aviators’ attitudes toward flying? Were they cavalier? Did they take unnecessary risks, or were they careful and methodical?”

Accidents happen.

Due to the detailed, scripted nature of NTSB procedures, the investigation may take up to a year to complete.

A few years ago a pilot’s engine failed and he was forced to make a water landing just off a beach. The ditching should have been survivable, but he lost consciousness on impact and sank with the airplane as it settled to the bottom in relatively shallow water. He drowned.

If he had been a diver, that would have been the end of the story. The public judgment would have been, “A diver drowned. He tried to breathe underwater; this is what happens.” But this victim happened to drown inside an airplane. So instead of the medical examiner simply saying that he drowned, the NTSB started its very thorough investigation procedures.

Fortunately, the pilot also had a surviving passenger. From the survivor’s statement, the aircraft’s maintenance records, and the mechanic’s testimony, an ugly story of reckless disregard for the most basic safety rules of flying began to emerge.

Do divers ever show a reckless disregard for basic safety rules? You bet. It’s unfortunate that the pilot died, but the events leading to his death were a useful reminder that the media in which we work and play, high-altitude air and water, are not forgiving. Humans are not designed for flying or diving, and nature only begrudgingly lets us trespass — on its terms.

The U.S. Navy and Coast Guard are chartered to investigate diving accidents. Unfortunately, there is a huge discrepancy in the number of personnel and the amount of funding for aviation accident investigations compared to diving accident investigations. The NTSB has hundreds of personnel and tens of millions in funding available, whereas the entire U.S. Navy has at most a handful of investigators with no investigation-specific funding.

Investigation team requirements

In the best of all worlds, an investigation team should have access to both a manned and an unmanned test facility, access to experts in all diving equipment (scuba, rebreathers, helmets), and the ability to conduct and interpret gas analyses — sometimes from minuscule amounts of remaining gas. At a minimum, such a team needs the ability to download and interpret dive computer/recorder data. Some investigations may require the simulation of UBA-human interactions for “re-enactment” purposes. An investigation team should also have diving medical expertise available to review medical examiner reports for consistency with known or discovered facts regarding the accident. Last, it should have in-depth knowledge of police investigative procedures, particularly of the procedures and documentation for maintaining “chain of custody”.

Do rebreather investigations have a future?

Considering the resources and time-frames required for laboratories such as the Navy Experimental Diving Unit (NEDU) to conduct diving equipment evaluations on a limited set of accident cases, and the unfunded costs associated with those investigations, it is difficult to imagine a resolution to an ever-increasing need for rebreather investigations. Almost certainly, no independent federal agency similar to the NTSB will ever be responsible for investigating diving accidents, simply because diving accidents lack national attention: the public at large is not being placed in jeopardy.

It is also unlikely that diving equipment manufacturers would welcome federal agency oversight and regulations comparable to those engendered by the FAA and NTSB. Diving might become exorbitantly expensive. For instance, if a $5 part available for purchase in an automotive store were to be used in an aircraft, it would become a $50–$500 part because of FAA required  documentation that it meets airworthiness standards.

The U.S. Coast Guard initiates diving accident investigations and in some cases conducts hearings into those accidents; however, with its enhanced role in Homeland Security, the Coast Guard is unlikely to welcome any efforts to diversify its mission. The cost/benefit ratio would appear to be too great.

For the future, as Dick Vann of DAN has suggested, the resolution may ultimately depend on rebreather users funding a team of dedicated, professional accident investigators. The cost of conducting worthwhile investigations has yet to be determined, and therefore the amount of funding needed to support it is unknown. I suggest that obtaining those estimates should be a priority as we, rebreather users and the industry, decide the next steps in investigating rebreather accidents.

 

The above are highlights from this author’s publication of the same name, found in: Vann RD, Mitchell SJ, Denoble PJ, Anthony TG, eds. Technical Diving Conference, Proceedings. Durham, NC: Divers Alert Network; 2009; 394 pages. ISBN# 978-1-930536-53-1.

This book is available for download at no cost as a PDF file from the Divers Alert Network website (http://www.DiversAlertNetwork.org/or from http://archive.rubicon-foundation.org/8300

Why Deep Saturation Diving Is Like Going to the Moon, and Beyond

This week, as the Space Shuttle is making its last circuits around our planet, I lament what has happened to our space program. Yet, I am reminded of another exploration program that has, like the shuttle and the moon programs, reached incredible milestones only to retreat to a less exotic but still impressive status. That other program is experimental, deep saturation diving.

I have been privileged to conduct human physiological research on several deep saturation dives, one being a record-breaking U.S. Navy dive at the Navy Experimental Diving Unit (NEDU) in 1977 to a pressure equivalent to that found at 1500 feet sea water (fsw), or 460 msw*, and on a 450 msw (1470 fsw) dive at the GUSI diving facility at the GKSS Institute in Geesthacht, Germany in 1990. For perspective, the safe SCUBA diving depth is considered to be 130 fsw, although technical and cave divers often descend deeper, to 300 fsw or so.

NEDU, Panama City, FL

Dives in hyperbaric chambers like at GUSI and NEDU are simulated; the divers don’t actually go anywhere. But the effects of the high pressure on the divers’ bodies are just as they would be in the ocean. Of course, even in simulated dives, divers wear Underwater Breathing Apparatus, and descend into water contained within the hyperbaric complex.

In 1979, NEDU again set the U.S. Navy record for deep diving to 1800 fsw (551 msw). At Duke University in 1981, the U.S. record for pressure exposure was set by three saturation divers inside an eight-foot diameter sphere. The internal pressure was 2250 fsw (686 msw). One of those divers went on to become the senior medical officer at NEDU, none the worse for his high pressure exposure.

The French company Comex, of Marseille used an experimental gas mixture of hydrogen-helium-oxygen to reach 675 msw, before being forced back to 650 msw due to physical and physiological problems with the divers. However, like teams attempting the summit of Mount Everest, one diver from the dive team was pressed to a world record of 701 msw (2290 fsw), just squeaking past the U.S. record.

There is a poorly understood physiological barrier called the High Pressure Nervous Syndrome (HPNS) that limits our penetration to ever deeper depths. In spite of the use of increasingly exotic gas mixtures, helium-oxygen in the U.S. Navy, helium-nitrogen-oxygen at Duke University, and hydrogen-helium-oxygen at Comex, all attempts to dive deeper have, to date, been rebuffed.

Just as I had thought as a young man that trips to the moon would be common-place by now, I had also assumed diving to 3000 feet would be routine. But it is not.

In my early research days I was interested in the effects on organisms of very high pressure, 5000 psi, which is equivalent to a depth of over 11,000 feet (3430 meters). We now know those effects can be profound, altering the very structure of cell membranes. Reversing those effects while maintaining high pressure, at great depth, is a daunting scientific task. We don’t yet know how to do it.

What we do know is that reaching 1500 feet can be done without too much difficulty. In the 1980s it became almost routine to dive to 1000 feet at both the Naval Medical Research Institute (Bethesda) and NEDU. Deep saturation diving is a thriving business in the oil fields of the Gulf of Mexico and the North Sea.

Click for a larger image.

But as for the similarity between deep saturation diving and NASA’s moon missions, in the Apollo program it took slightly over three days to get to the moon, and almost an equal time to return. But as the above dive profile shows, it took sixteen days to reach the maximum depth of 1500 fsw, and seventeen days to safely return. Over that period of time astronauts would have whizzed past the moon and been well on their way to Mars. Unlike spacecraft and astronauts, divers must slow their descent to avoid HPNS, and must slow their return to the surface to avoid debilitating and painful decompression sickness. Diving without submarines or armored suits is very much a demanding, physical stress.

Politically, exceeding our current depth limits of approximately 2000 feet is akin to returning to the moon, and going beyond. We could do it, but at what cost? Should we? Will it ever be a national priority?

Maybe not for the United States, but I have a suspicion that other countries, perhaps not as heavily committed to space as we, will find the allure of beating current diving records irresistible. If there are medical or pharmacological interventions developed for getting divers safely and productively down to 3000 feet, then that would be a scientific achievement comparable to sending men to Mars.

*[The feet to meters conversion is slightly different from the feet of sea water to meters of sea water conversion. The latter represents pressure, not depth, and therefore includes a correction factor for the density of sea water.]

My Pathway to Writing – Learning from Max McCoy’s “The Moon Pool”

This is not some random book review. I have a personal investment in Max McCoy’s underwater thriller, and to be honest, Max is a friend and mentor.

As the Scientific Director and Senior Scientist of the Navy Experimental Diving Unit (NEDU), I get some unusual calls from time to time. One of the most memorable was from a novelist, Max McCoy.

Not being an avid reader of Westerns, I had never heard of Max, but he had an interesting question. He wanted to know if our large, high pressure chamber, called the Ocean Simulation Facility, could be used to depressurize a small submarine. He gave me the dimensions of the submarine, and little other information to go on.

The unequivocal answer was yes, it could be done fairly easily. With that affirmation, Max traveled to NEDU. After touring our facilities and meeting with our Commanding Officer, engineers, scientists, and submarine medical officers, he began sketching out a closing chapter of his manuscript, the Moon Pool. NEDU would be prominently featured.

During his visit, over lunch, we talked a little about my non-fiction writing project, a spiritual/supernatural collection of carefully filtered anecdotes. He encouraged me in my efforts, and even shared an amazing story of his own. But what Max did not know was that I was stuck in the style of science writing that had been the mainstay of my scientific career. It was hard writing, and frankly, hard reading as well.

When Max returned to Kansas, he sent me his manuscript, which I devoured. The Moon Pool was a change of pace for Max as well. He had been an avid diver for years, and had a diving related story brewing in his mind for some time. For him, The Moon Pool was a welcome, if temporary, release from the Western genre for which he was so well-known.

When I finished the manuscript I began an almost maniacal writing session of my own — an all nighter — writing how I thought the NEDU chapter should read. Since no one would see it, I featured myself and my buddies, inserting our characters into the story, and with a plausible and action-filled story line. I had never had so much fun writing — the words spilled out of my head onto the keyboard.

I sat on that secret product for probably a week before I told Max what I had done. He asked to see it, and much to my surprise, he and his publisher liked it. Even more to my surprise, my character and those of my friends ended up in the last chapter of Moon Pool, modified of course to meet Max’s needs. That book, published in 2004, has a treasured place in my office at NEDU.

On the back cover is my blurb, “A one-of-a kind underwater thriller. The sinister beauty of the underwater world is painted in hues that only an avid diver and inspired novelist could capture.” On the front cover, my dear friend Bob Barth, the Navy’s first Aquanaut, wrote, “A great book! Compelling stuff.” By the time Max visited us, Bob had authored his own book on the Navy’s historical Sea Lab program.

I owe a great deal to Max, for he taught me just how fun creative writing can be, and how, with proper guidance, it can be turned into a commercial product. I have since written two books, one written in record pace, for me at least.  The novel, working title “Children of the Middle Waters” is a mixed military-science fiction story that involves my favorite things, flying and diving, with a pinch of top-secret government intrigue;  just another day at NEDU.  After a long gestational period, I used the creative writing skills developed in the novel to improve the style of the spiritual/supernatural manuscript. Both Children of the Middle Waters, and the spiritual book have yet to be published. But I’m optimistic that will happen in good time.

I will discuss those works more in upcoming blog posts.

By the way, Max’s Moon Pool begins with a supernatural event that is tantalizing in its originality. Furthermore, my spiritual book contains an anecdote of a supernatural experience Max experienced when young. Finally, as a tribute to Max McCoy, he is the inspiration for an investigative journalist in Children of the Middle Waters.

In retrospect, that was quite an auspicious phone call I took one day eight years ago.

Below are links to Max’s web site and his writer’s blogs.

http://www.maxmccoy.com/

http://www.maxmccoy.blogspot.com/

http://www.signalsandnoise.net

 

My Top Three Diving Sites: The Great Barrier Reef, Australia

My Navy travels have afforded me the privilege of diving in some of the most interesting places. In this, and the next couple of posts, I list my top three diving destinations.

I’ve been diving on the Australia’s Great Barrier Reef on two occasions, both times departing for the reef from Cairns, pronounced like the first syllable in “Kansas”. The first trip was to the inner reef, a short boat ride away from the docks. That experience was OK, but not what I had expected. It seemed like the reef had been abused by massive diver and snorkler populations which had not treated the reef with the respect it deserved.

On my second trip to Australia on Navy diving  business, I traveled with the Commanding Officer of the Navy Experimental Diving Unit, CDR (later CAPT)  Jim Wilkins.

Two NEDU Divers - Jim Wilkins and John Clarke (the short one)

From Cairnes we took a fast boat to a liveabord vessel anchored on the outer reef. It was a beautiful 140 ft. tall schooner, SV Atlantic Clipper. And that made all the difference.

During the diving season the Clipper is stationed on the outer reef, and shuttles divers to four diving locations; Norman Reef, Saxon Reef, Hastings Reef, and Michaela’s Reef. Each location featured different underwater vistas, showing an overwealming diversity of colorful reef animals. On a typical day we’d make three daylight dives of varying depths plus a night dive.

SV Atlantic Clipper

After one memorable night dive we walked up the long gangway to the deck, shed, cleaned and stowed our dive gear, and then, attracted by commotion at the bow, found a cluster of divers feeding large fish while six or more Bronze Whaler sharks circled amongst the fish, which seemingly paid the sharks no mind at all. The fish knew where the sharks were at all times, and only the healthiest, quickest fish dared feed in such proximity to the large predator. The agile fish apparently felt confident they could dodge the far more cumbersome sharks, because while we watched, not a sinlge fish was taken.

I, on the other, was not quite so agile. And I admit that it bothered me a bit that while I had been swimming through the dark to a dive ladder on the port side of the vessel, near the stern, Bronze Whalers were circling alongside the port bow. But the ship’s crew assured me that the Bronze Whalers were “not particularly dangerous.”  They had attacked spearfisherman and “bathers”, but the attacks had not been fatal.

Well, that’s comforting, I thought.

I have to say the most memorable series of dives were with the magnificent Green sea turtles. To observe such beautiful and docile creatures in their native environment was probably the highlight of the entire trip.

 During one of the many dives I learned a valuable lesson about diving with diveboat gear. Through the years I’d been diving, since 1964, the equipment was either my own, or belonged to the Navy, and was always maintained in like-new condition. It may have looked battered, but mechanically it was pristine.
As Jim Wilkins and I descended through 60 feet on one dive, I noticed my regulator was becoming increasingly difficult to breathe. I checked my bottle pressure, and there was plenty of air – the dive was just starting. But whether I understood it or not, it was becoming harder and harder to breathe – by the second. I finally took action by grabbing my dive-buddy’s octopus regulator (a back-up regulator), and together we slowly ascended to the surface.
Back on the boat I discovered my tank valve was not fully turned on. Why not, I wondered?
Well, the valve was worn, and generated a considerable resistance before it was fully open. As I am accustomed, I had turned the valve until I met resistance and stopped. That is a good way to prevent damaging a well working valve, but that particular tank valve was not working as smoothly as it should. It fooled me.
Chalk one up to lessons learned.
Without a doubt, the series of dive made from the Atlantic Clipper were among the most memorable of my diving career. In upcoming posts I’ll describe Red Sea dives at Sharm El Sheik and Ras Mohammad, followed by a dive at Herod’s Port, in old Caesarea, Israel.