Hydrogen Diving – A Very Good Year for Fiction

Susan R. Kayar

It is incredibly unlikely that two scientist colleagues, Susan Kayar and myself, separated by large amounts of time and distance, would independently publish two novels about deep hydrogen saturation diving, in the same year. Unlikely or not, it happened in 2017. Neither author was aware of the other’s intentions, or even their whereabouts.

Some things are inexplicable.

Hydrogen diving is, to use an over-used analogy, a double edged sword. On the one hand it makes truly deep diving possible, yet it can cause bizarre mental effects on some deep hydrogen divers. And that dichotomy is grist for any novelist’s mill.

I had previously written  about hydrogen diving and the pioneering role a Swede named Arne Zetterström had in developing it. Unfortunately, perhaps because he was a bold diver, he did not survive to become an old diver. Ironically, his death while diving wasn’t the fault of the hydrogen, but of his inattentive tenders. But as they say, that’s another story.

Once the remarkable, serendipitous co-publication of these two hydrogen diving novels became known, Kayar and I decided to post reviews, each about the other’s book. After all, if we didn’t, no one else would.

Quoting from Dr. Kayar’s biography listed on her Goodreads site, “Susan R. Kayar holds a doctorate in biology from the University of Miami. Her research career in comparative respiratory physiology spanned more than twenty years. She was the head of a research project in hydrogen diving and hydrogen biochemical decompression in animal models at the Naval Medical Research Institute, Bethesda, Maryland. She currently resides in Santa Fe, New Mexico, with her husband Erich; they met when they were both performing research at NMRI. Dr. Kayar was inducted into the Women Divers Hall of Fame in 2001 for her contributions to the study of diving physiology and decompression sickness.”

As for me, my bio is included in the About page of this blog.

My review of her book, Operation SECOND STARFISH: A Tale of Submarine Rescue, Science, and Friendship, is repeated here, and her review of mine is at the bottom of this post.

“Submarine deep sea “black ops” can be risky business even when everything goes well. But when things go badly, submariners’ lives are in peril, and everyone is praying for a miracle, and a savior. This well written novel drops you into the middle of such a desperate situation, and the potential savior, or potential scapegoat, is an unexpected protagonist, a female civilian scientist who knows the Navy way, knows how to motivate Navy divers, and unconsciously toys with their affections. This is a sensitively written account with a focus as much on interpersonal relations as on the technical aspects of hydrogen diving and biological decompression, or “Biodec.” Some of the greatest themes in this story are of the personal heroism of divers willing to risk their lives in the cold, foreboding darkness of the deep sea in an improbable effort to save fellow sailors.

The story may be fictional, but the science is not. In fact, for all the reader knows, everything written could have happened, or perhaps will, the next time the Navy has a submarine stranded on the bottom. The author, Susan Kayar, Ph.D. has pursued with Navy funding the very technology exposed in this story.

Amazingly, this is one of two novels published independently by scientists in the same year concerning record breaking deep hydrogen dives conducted on super-secret national security missions. That is a rare coincidence indeed, since to my knowledge no other novels about deep hydrogen diving have ever been written.

The other book is a sci fi techno-thriller called Triangle: A Novel, the second volume of a trilogy published by one of Kayar’s fellow scientists and colleagues, this reviewer. In both books, the hazards of deep diving are very real, and the tension is palpable. If you want to learn of the possibilities and perils of deep hydrogen diving, and experience the heroism of exceptional men and women in extraordinary circumstances, you now have two books to both entertain and painlessly inform you.

Kayar’s book will leave you wishing you could ride along with Doc Stella as she rides off into the sunset on her Indian motorcycle. What a ride it is.”


Kayar’s review of my novel, Triangle, the second in the Jason Parker Series of science fiction thrillers, follows.

“I thoroughly enjoyed Triangle, the second novel in the Jason Parker Trilogy by John Clarke. It is a fun and engaging mash-up of diving science and science fiction. John and I worked together in diving research for the Navy in Maryland years ago. He continues to this day to perform diving research for the Navy in Florida (while I moved on to other activities and then retired). As one would expect, his details in diving science and Navy jargon are impeccable. But it is impressive that his characters are well drawn and his plot twists are creative and bold.

My favorite part of Triangle has to be the ultra-deep hydrogen dive sequence for admittedly personal reasons. John and I, friendly colleagues though we were, had not been in contact with each other for a couple of decades or more. And yet my own diving novel, Operation SECOND STARFISH, was published in the same year as Triangle, and also contains an ultra-deep hydrogen dive sequence. Mutual friends had to tell us that the other had published a book for us to re-establish contact. I would imagine that our two books are the only novels ever to describe a hydrogen dive, which is a huge technical and physiological challenge, as readers will discover. John’s hydrogen dive works out (if I dare say so without revealing too much of his excellent plot) about as well as such a dangerous scenario ever will. My hydrogen dive is a lot rougher, in keeping with the more aggressive compression rate chosen to respond to the disabled submarine rescue that forms the basis of my story.

Any readers truly interested in dives well beyond 1000 feet of seawater will find a lot to learn and marvel over in Triangle. Readers just along for the exciting sci-fi ride will be equally happy to have spent time in John Clarke’s imaginative world. I look forward to his predicted December release of the third novel in this series.”


Anyway you look at it, these two fun novels contain a cram course in the rarest type of diving there is, diving with hydrogen as a breathing gas.


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.

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.


Separator small

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


After the Heart Attack – The Healing Power of Athletic Passions

DSC06084-B2There is nothing quite like a heart attack and triple bypass surgery to get your attention.

Even if you’ve been good, don’t smoke, don’t eat to excess, and get a little exercise, it may not be enough to keep a heart attack from interrupting your life style, and maybe even your life.

Post-surgical recovery can be slow and painful, but if you have an avocational passion, that passion can be motivational during the recovery period after a heart attack. There is something about the burning desire to return to diving, flying, or golfing to force you out of the house to tone your muscles and get the blood flowing again.

My return to the path of my passions, diving and flying, began with diet and exercise. My loving spouse suggested a diet of twigs and leaves, so it seemed. I can best compare it to the diet that those seeking to aspire to a perpetual state of Buddha-hood, use to prepare themselves for their spiritual end-stage: it’s a state that looks a lot like self-mummification. Apparently those fellows end up either very spiritual or very dead, but I’m not really sure how one can tell the difference.

The exercise routine began slowly and carefully: walking slowly down the street carrying a red heart-shaped pillow (made by little lady volunteers in the local area just for us heart surgery patients). The idea, apparently, is that if you felt that at any point during your slow walk your heart was threatening to extract itself from your freshly opened chest, or to extrude itself like an amoeba between the stainless steel sutures holding the two halves of your rib cage together, that pillow would save you. You simply press it with all the strength your weakened body has to offer against the failing portion of your violated chest, and that pressure would keep your heart, somehow, magically, in its proper anatomical location.

I am skeptical about that method of medical intervention, but fortunately I never had occasion to use it for its avowed purpose.

Eventually I felt confident enough to ditch the pillow and pick up the pace of my walks. In fact, I soon found I could run again, in short spurts. It was those short runs that scared the daylight out of my wife, but brought me an immense amount of pleasure.  It meant that I might be able to regain my flying and diving qualifications.

Three months later I was in the high Arctic with good exercise capability, and most importantly the ability to sprint, just in case the local polar bears became too aggressive on my nighttime walks back from the only Ny-Alesund pub.

Stress test, Public Domain, from Wikimedia Commons.

After that teaching adventure, I prepared myself for the grinder that the FAA was about to put me through: a stress test. Not just any stress test mind you, but a nuclear stress test where you get on a treadmill and let nurses punish your body for a seeming eternity. Now, these nurses are as kindly as can be, but they might well be the last people you see on this Earth since there is a small risk of inducing yet another heart attack during the stress test. Every few minutes the slope and speed of the treadmill is increased, and when you think you can barely survive for another minute, they inject the radioisotope (technetium 99m).

With luck, you would have guessed correctly and you are able to push yourself for another long 60-seconds. I’m not sure exactly what would happen if you guess incorrectly, but I’m sure it’s not a good thing.

And then they give you a chance to lie down, perfectly still, while a moving radioisotope scanner searches your body for gamma rays, indicating where your isotope-laden blood is flowing. With luck, the black hole that indicates dead portions of the heart will be small enough to be ignored by certifying medical authorities. (An interesting side effect of the nuclear stress test is that you are radioactive for a while, which in my case caused a fair amount of excitement at large airports. But that’s another story.)

The reward for all the time and effort spent on the fabled road to recovery, is when you receive, in my case at least, the piece of paper from the FAA certifying that you are cleared to once again fly airplanes and carry passengers. With that paper, and having endured the test of a life-time, I knew that I’d pass most any diving physical.

IMG_0645 (2014_06_22 07_00_11 UTC)
Vortex Springs, 2010

Having been in a situation where nature dealt me a low blow and put my life at risk and, perhaps more importantly, deprived me of the activities that brought joy to my life, it was immensely satisfying to be able to once again cruise above the clouds on my own, or to blow bubbles with the fish, in their environment. Is there anything more precious that being able to do something joyful that had once been denied?

A goofy looking but very happy diver sharing a dive with his Granddaughter, July 2014.











Separator small

Without a doubt, the reason I was able to resume my passions was because I happened to do, as the physicians said, “all the right things” when I first suspected something unusual was happening in my chest. The symptoms were not incapacitating so I considered driving myself to the hospital. But after feeling not quite right while brushing my teeth, I lay down and called 911. The ambulance came, did an EKG/ECG, and called in the MI (myocardial infarction) based on the EKG. The Emergency room was waiting for me, and even though it was New Years’ eve, they immediately called in the cardiac catheterization team. When the incapacitating event did later occur I was already in cardiac ICU and the team was able to act within a minute to correct the worsening situation.

Had I dismissed the initial subtle symptoms and not gone to the hospital, I would not have survived the sudden onset secondary cardiac event.

The lesson is, when things seem “not quite right” with your body, do not hesitate. Call an ambulance immediately and let the medical professionals sort out what is happening. That will maximize your chances for a full and rapid recovery, and increase the odds of your maintaining your quality of life.

It will also make you appreciate that quality of life more than you had before. I guarantee it.

Does Your Rebreather Scrubber Operate in Its Goldilocks Zone?

Exoplanet Gliese 581d, orbiting the red-dwarf star Gliese 581, only 20 light-years away. (The existence of this planet is currently in dispute.)

In space, there is a so-called Goldilocks zone for exoplanet habitability. Too close to a star, and the planet is too hot for life. Too far from its star, and the planet is too cold for life, at least as we understand biological life, life dependent on water remaining in a liquid state. Earth is clearly in the Goldilocks zone, and so is a purported planet Gleise 581d, from another solar system.

Carbon dioxide absorbing “scrubber” canisters in rebreathers have similar requirements for sustaining their absorption reactions. If it’s too hot, the water necessary for the absorption reaction is driven off. Too cold and the water cannot fully participate in the absorption reactions.

Those with some knowledge of chemistry recognize that cold retards chemical reactions and heat accelerates them. But that does not necessarily apply to reactions where a critical amount of water is required. Water thus becomes the critical link to the reaction process, and so maintaining scrubber temperature within a relatively narrow “Goldilocks” zone is important, just as it is for life on distant planets.

Temperature within a scrubber canister is a balance of competing factors. Heat is produced by the absorption of CO2 and it’s conversion from gas to solid phase, specifically calcium carbonate. A canister is roughly 20°C or more warmer than the surrounding inlet gas temperature due to the heat-generating (exothermic) chemical reactions occurring within it.

Heat is lost from a warm canister through two heat transfer processes; conduction and convection. Conduction is the flow of heat through materials, from hot to cold. Hot sodalime granules have their heat conducted to adjacent cooler granules, and when encountering the warm walls of the canister, heat passes through the canister walls, and on to the surrounding cold water.

You can think of this conduction as water flowing downhill, down a gravity gradient. But in this case, the downhill is a temperature gradient, from hot to cold. If the outside of the canister was hotter than the inside, heat would flow in the opposite direction, into the canister.

Copper is a better conductor of heat than iron (it has a higher thermal conductivity), explaining why copper skillets are popular for cooking on stoves. Air is a poor conductor of heat, explaining why neoprene rubber wet suits, filled with air bubbles, are good insulators. Air-filled dry suits are an even better insulator.

Chemical absorption reactions heat an otherwise cold canister (yellow is hot, red is warm, black is cold.) (Copyright John R. Clarke, 2014).

Convection is the transfer of heat to a flowing medium, in this case gas. You experience convective cooling when you’re working hard, generating body heat, and a cool dry breeze passes over your skin. Convective cooling can, under those circumstances, be delightful.

When you walk outside on a cold, windy day, convective cooling can be your worst enemy. Meteorologists call it wind chill.

There is wind chill within a canister, caused by the flow of a diver’s exhaled breath through the canister. In cold water the diver’s exhaled breath leaves the body quite warm, but is chilled to water temperature by the time it reaches the canister. Heat is lost through uninsulated breathing hoses exposed to the surrounding water.

As you might expect, if the canister is hot, that convective wind chill can help cool it. If the canister is cold, then the so-called wind chill will chill it even more.

Copyright John R. Clarke, 2014.

The amount of heat transferred from a solid object to gas is determined by three primary variables; the flow rate of the gas, the density of the gas, and the gas’s heat capacity. Heat capacity is a measure of the amount of heat required to raise the temperature of a set mass of gas by 1° Celsius.

Both the heat capacity and density  of the gas circulating through a rebreather changes not only with depth (gas density), but with the gas mixture (oxygen plus an inert diluent such as nitrogen or helium).  The heat capacity of nitrogen, helium and oxygen differ, and the ratio of oxygen and inert gas varies with depth to prevent oxygen toxicity. Nitrogen and helium concentrations vary as well,  as the diver attempts to avoid nitrogen narcosis. Capture2

Q is heat transferred by convection, and the terms on the right are, in sequence, diver ventilation rate, gas density, heat capacity of the inspired gas mixture at constant pressure, and the difference in temperature between the absorbent and environmental temperature.

The interaction of all these variables can be complex, but I’ve worked a few examples relevant to rebreather diving. The assumptions are a low work rate: ventilation is 22 liters per minute, water temperature is 50°F (10°C), oxygen partial pressure is 1.3 atmospheres, and dive depths of 100, 200 and 300 feet sea water. The average canister temperature is assumed to be 20°C (68°F) above water temperature, a realistic value found in tests of scrubber canister temperatures by the U.S. Navy.

The heat capacities for mixtures of diving gases come from mixture equations, and for the conditions we’re examining are given in the U.S. Navy Diving Gas Manual. (This seems to be a hard document to obtain.)

At 100 fsw, the heat transfer (Q) for a nitrogen-oxygen (nitrox) gas mixture is 34.2 Watts (W). For a helium-oxygen mixture (heliox), Q is 27.4 W.  At 200 fsw, Q for nitrox is 59.9 W, and for heliox Q is 50.3 W. At 300 fsw, Q for nitrox gas mixture is 85.5 W, and for heliox, is 59.9 W.

Interestingly, the heat transferred from the absorbent bed to the circulating gas is the same at 300 fsw with heliox as it is at 200 fsw with nitrox.

Photo courtesy of David L. Conlin, Ph.D., Chief – National Parks Service Submerged Resources Center. Photo by Brett Seymour, NPS.

Dr. Jolie Bookspan briefly mentioned the fact that helium removes less heat from a diver’s airways than does air in her short article on “The 36 Most Common Myths of Diving Physiology” (see myth no. 20). Conveniently, heat exchange equations apply just as well to inanimate objects like scrubber canisters as they do to the human respiratory system.

From these types of heat transfer calculations it is easy to see that for a given depth, work rate and oxygen set point, it is better to use a heliox mixture than a nitrox mixture if you’re in cold water. That may sound counterintuitive considering helium’s high thermal conductivity, but the simple fact is, the helium background gas with its low density carries away less heat from the canister, and thereby keeps the canister warmer, than a nitrox mixture does. The result is that canister durations are longer in cold water if less heat is carried away.

In warm water, the opposite would be true. Enhanced canister cooling with nitrox would benefit the canister.

An earlier post on the effect of depth on canister durations raised the question of whether depth impedes canister performance. The notion that increased numbers of inert gas molecules block CO2 from reaching granule absorption sites has little chemical kinetic credence. However, changing thermal effects on canisters with depth or changing gas mixtures does indeed affect canister durations.

I’ve just given you yet another reason why helium is a good gas for rebreather diving, at least in cold water. Unfortunately, these general principles have to be reconciled with the specific cooling properties of all the rebreather canisters in current use. In other words, your canister mileage may vary. But it does look like the current simple notions of depth effects are a bit too simplistic.






How Cold Can Scuba Regulators Become?

The Arctic science diving season is in full swing (late May). Starting in September and October, the Austral spring will reach Antarctica and science diving will resume there as well.

Virtually all polar diving is done by open-circuit diving, usually with the use of scuba. Picture046

As has often been reported, regulator free flow and freeze up is an operational hazard for polar divers. However, even locations in the Great Lakes and Canada, reachable by recreational, police and public safety divers, can reach excruciatingly cold temperatures in both salt and fresh water on the bottom.

Sherwood Fail

Decades ago a reputed Canadian study measured temperatures in a scuba regulator, and found that as long as water temperature was 38° F or above, temperatures within the second stage remained above zero.

Recent measurements made on modern high-flow regulators at the U.S. Navy Experimental Diving Unit show that the thermal picture of cold-water diving is far more complex than was understood from the earlier studies.

NEDU instrumented a Sherwood Maximus regulator first and second stage with fast time response thermistors. The regulators were then submerged in 42°, 38°, and 34° F fresh water, and 29° F salt water, and ventilated at a heavy breathing rate (62.5 liters per minute), simulating a hard working diver.

In the following traces, the white traces are temperatures measured within the first stage regulator after depressurization from bottle pressure to intermediate pressure. That site produces the lowest temperatures due to adiabatic expansion. The red tracing was obtained at the inlet to the second stage regulator. The blue tracing was from a thermistor placed at the outlet of the “barrel” valve within the second stage regulator box. Theoretically, that site is exposed to the lowest temperatures within the second stage due to adiabatic expansion from intermediate pressure to ambient or mouth pressure.

Regulators were dived to 198 ft (60.4 meters) and breathed with warm humidified air for 30-minutes at the 62.5 L/min ventilation rate. The regulator was then brought to the surface at a normal ascent rate.

To make the breathing wave forms more distinct, only one minute of the 30-minute bottom time is shown in the following traces, starting at ten minutes.

The first two tracings were at a water temperature of 42° F. In the first tracing, bottle pressure was 2500 psi, and in the second, bottle pressure was 1500 psi. (For all of these photos, click the photo for a larger view.) 42 2500 SM2

Color code

Color coding of thermistor locations, all internal to the regulator.

42 1500 SM2



When bottle pressure was reduced from 2500 psi to 1500 psi, all measured temperatures increased. The temperature at the entrance to the second stage oscillated between 0° and  1°C. At 2500 psi that same location had -1 to -2°C temperature readings.






The next two tracings were taken in 29° F salt water. The coldest temperatures of the test series were in 29° F water with 2500 psi bottle pressure.

29 1500 SM2

29 2500 SM2










As a reminder, 32°F is 0°C,  -22° C is equal to -7.6° F, and -11°C is 12.2°F. At a bottle pressure of 2500 psi, the temperature inside the second stage (blue tracing) never came close to 0° C. So we’re talking serious cold here. No wonder regulators can freeze.

Frozen Reg 1_hide


Separator small

This material was presented in condensed form at TekDiveUSA 2014, Miami. (#TekDiveUSA)


I Too Landed at the Wrong Airport

As a professional in underwater diving, and an amateur airman, I’ve been thinking a lot lately about the causes of accidents and “near-misses”. If you’re reading this in early 2014, you are no doubt aware of several recent incidents of commercial and military jets landing at the wrong airport. In the latest case there was a potential for massive casualties, but disaster was averted at the last possible moment.

As they say, to err is human. From my own experience, I know the truth of that adage in science, medicine, diving, and the subject of this posting, aviation. Pilot errors catch everyone’s attention because we, the public, know that such errors could personally inconvenience us, or worse. But lesser known are the sometimes subtle factors that cause human error.

I can honestly tell you  exactly what I was doing and thinking that caused errors at the very end of long flights. Those errors, none of which were particularly dangerous or newsworthy, were nonetheless caused by the same elements that have been discovered in numerous fatal accidents. Namely, what I was seeing, was not at all what I thought I was seeing.

The small but capable Cessna 150B.

Long before the advent of GPS navigation, cell phones and electronic charts,  I was flying myself and an Army friend (we had both been in Army ROTC at Georgia Tech) from Aberdeen Proving Ground, MD to Georgia. I was dropping him off in Atlanta at Peachtree-Dekalb Airport, and then I would fly down to Thomasville in Southwest Georgia where my young wife awaited me.

Since it was February most of the planned six hour flight was at night. We couldn’t take-off until we both got off duty on a Friday.

I had planned the flight meticulously, but I had not counted on the fuel pumps being shut down at our first planned refueling spot. After chatting with some local aviators about the closest source of fuel, we took off on a detour to an airport some thirty miles distant. That unplanned detour was stressful, as I was not entirely sure we’d find fuel when we arrived. Fortunately, we were able to tank up, and continue on our slow journey. We were flying in my 2-seat Cessna 150, and traveling no faster than about 120 mph, so the trip to Atlanta was a fatiguing and dark flight.

As we eventually neared Atlanta, I was reading the blue, yellow and green paper sectional charts under the glow of red light from the overhead cabin lamp. Lights of the Peachtree-Dekalb airport were seemingly close at hand, surrounded by a growing multitude of other city lights. Happy that I was finally reaching Atlanta, I called the tower and got no answer. No matter, it was late, and many towers shut down operations  fairly early, about 10 PM or so. So I announced my position and intentions, and landed.

The runway was in the orientation I had expected, and my approach to landing was just as I had planned. However, as I taxied off the runway, I realized the runway environment was not as complex as it should have been. We taxied back and forth for awhile trying to sort things out, before I realized I’d landed 18 nautical miles short of my planned destination.

My unplanned refueling stop in South Carolina placed me far enough off course to take me directly over an airport that looked at night like my destination, Peachtree-Dekalb, Atlanta. (Solid line: original course, dashed line: altered course.)

I had so much wanted that airport to be PDK, but in my weariness I had missed the signs that it was not. I had landed at Gwinnett County Airport, not Peachtree-Dekalb.

No harm was done, but my flight to Thomasville was seriously delayed by the two extra airport stops. It was after 1 AM before I was safe at the Thomasville, GA airport, calling my worried wife to pick me up.

She was not a happy young wife.

A few years later, I added an instrument ticket to  my aviation credentials, and thought that the folly of my youth was far behind me. Now, advance quite a few decades, to a well-equipped, modern cross-country traveling machine, a Piper Arrow with redundant GPS navigation and on-board weather. I often fly in weather, and confidently descend through clouds to a waiting runway. So what could go wrong?

Piper Arrow 200B at home in Panama City, Fl.

Wrong no. 2 happened when approaching Baltimore-Washington International airport after flying with passengers from the Florida Panhandle. Air Traffic Control was keeping me pretty far from the field as we circled Baltimore to approach from the west. I had my instrumentation set-up for an approach to the assigned runway, but after I saw a runway, big and bold in the distance, I was cleared to land, and no longer relied on the GPS as I turned final.

As luck would have it, just a minute before that final turn we saw President George W. Bush and his decoy helicopters flying in loose formation off our port side. I might have been a little distracted.

In the city haze it had been hard to see the smaller runway pointing in the same direction as the main runway. So I was lining up with the easy-to-see large runway, almost a mile away from where I should have been. It was the same airport of course, but the wrong parallel runway.

I was no doubt tired, and somewhat hurried by the high traffic flow coming into a major hub for Baltimore and Washington. Having seen what I wanted to see, a large runway pointed in the correct direction, I assumed it was the right one, and stopped referring to the GPS and ILS (Instrument Landing System) navigation which would have revealed my error.

The tower controller had apparently seen that error many times before and gently nudged me verbally back on course. The flight path was easily corrected and no harm done. But I had proven to myself once again that at the end of a long trip, you tend to see what you want to see.

Several years later I had been slogging through lots of cloud en-route to Dayton, Ohio. I had meetings to attend at Wright Patterson Air Force base. It was again a long flight, but I was relaxed and enjoying the scenery as I navigated with confidence via redundant GPS (three systems operating at the same time).

As I was approaching Dayton, Dayton Approach was vectoring me toward the field. They did a great job I thought as they set me up perfectly for the left downwind at the landing airport. But then I became a bit perturbed that they had vectored me almost on top of the airport and then apparently forgotten about me. So I let them know that I had the airport very much in sight. They switched me to tower, and I was given clearance to land.

As I began descending for a more normal pattern altitude, the Dayton Tower called and said I seemed to be maneuvering for the wrong airport. In fact, I was on top of Wright Patterson Airbase, not Dayton International.

Rats! Not again.

Dayton airports
Wish my electronic Foreflight chart on my iPad had these sorts of markings.

Well, the field was certainly large enough, but once again I had locked eyes on what seemed to be the landing destination, and in fact was being directed there by the authority of the airways, Air Traffic Control (ATC). And so I was convinced during a busy phase of flight that I was doing what I should have been doing, flying visually with great care and attention. However, I was so busy that my mind had tunnel vision. I had once again not double checked the GPS navigator to see that I was being vectored to a large landmark which happened to lie on the circuitous path to the landing airport. (I wish they’d told me that, but detailed explanations are rarely given over busy airwaves.)

Oddly enough, if I had been in the clouds making an instrument approach, these mind-bending errors could not have happened. But when flight conditions are visual, the mind can easily pick a target that meets many of the correct criteria like direction and proximity, and then fill in the blanks with what it expects to see. In other words, it is easy in the visual environment to focus with laser beam precision on the wrong target. With all the situational awareness tools at my disposal, they were of no use once my brain made the transition outside the cockpit.

To be fair, distracting your gaze from the outside world to check internal navigation once you’re in a critical visual phase of approach and landing can be dangerous. That’s why it’s good to have more than one pilot in the cockpit. But my cockpit crew that day was me, myself and I; in that respect I was handicapped.

Apparently, even multiple crew members in military and commercial airliners are occasionally lulled into the same trap. At least that’s what the newspaper headlines say.

My failings are in some ways eerily similar to reports from military and commercial incidents. Contributing factors in the above incidents are darkness, fatigue, and distraction. When all three of these factors are combined, the last factor that can cause the entire house of cards, and airplane, to come tumbling down, is the brain’s ability to morph reality into an image which the mind expects to see. Our ability to discern truth from fiction is not all that clear when encountering new and unexpected events and environments.

The saving grace that aviation has going for it is generally reliable communication. ATC saved me from major embarrassment on two of these three occasions.

I only wish that diving had as reliable a means for detecting and avoiding errors.












The Aesthetics of Flying in Clouds

When it comes to vocations and avocations, I know of none more aesthetically pleasing than flying and diving. I’m sure there are many others, but I simply don’t know them.

My vocation is diving, and flying is my avocation. I also know commercial pilots who dive in caves simply for the joy of diving. Those two activities, flying and diving, are fairly similar, as I’ve noted before.

There are experiences in flying and diving that make them more than enjoyable. They are actually breathtaking, when one takes the time to appreciate them.

For me, the breath taking part is flying into and out of clouds; what is called instrument flying. It’s called that because when you’re in clouds you can’t see the horizon, and you can’t trust bodily sensations, so you are entirely dependent upon your aircraft instruments to make sure you, your passengers, and the aircraft, do not come to harm.

Granted, there are times during an instrument flight when you see absolutely nothing outside the aircraft. Some have compared it to flying inside a milk bottle, which is in my opinion an apt analogy. If it happens to be smooth flight, then there is no sensation of flight at all. The electronic equipment counts down the miles, but as far as you can tell you are in aerial limbo, seemingly suspended in time and space, encroaching on the edges of the twilight zone. 

But when you eventually break out of those clouds, you instantaneously switch from sensory deprivation to sensory overload. The view can be spectacular. 


When I was an instrument student, long before GPS navigation, instrument flying was hard work, especially when training. It still is in many ways, but technology has made flight in the clouds more precise, and frankly easier over all than it used to be.

But in the clouds a pilot is still too busy “aviating, navigating, and communicating”, to catch more than a brief glance outside, to enjoy the ever shifting textures of white clouds, blue sky and a multitude of grays in between. Occasionally you spy greens and browns of the ground, seen fleetingly through breaks in the cloud cover.

It is a grand theater in the sky not visible from the ground. For that reason, it is special, and to be seen in that moment and that place by no one else in the world except you and your passengers.

The video below gives a sample of such variable flows of scenery, with visibility ranging from zero to miles. The entire flight looped around my home airport in Panama City, FL, as I was radar vectored along a large rectangle, eventually joining a course bringing the aircraft back to a straight-in approach for landing.

This particular flight was a currentcy flight, so the departure and approach to landing was repeated several times. The video, however, ends just after I set up the navigation devices for the next approach. (I suggest you watch the video full screen at the highest resolution possible – 1440p HD.)

The only way I can hope to describe the beauty of such a flight is through the music which accompanies it. The quietness, the excitement, is all there. And from one who has experienced all those emotions during the flight, I can attest to the relevance of that music.






The Sojourner’s Dilemma; You Have to Go Home Sometime

There are sports, there are professions, then there are sojourns.

Astronauts are sojourners, as are pilots and mountain climbers and underwater divers. While the sojourner may have carefully planned his sojourn, warding off potential trouble by using good equipment and training, it is the return to normalcy that oftentimes presents the greatest and most unexpected danger.

Mt. McKinley, or Denali.

Mountain climbers who reach the top of their mountain, don’t always make it safely back down. Astronauts reentering the atmosphere understand the risk of return all too well.

For scuba divers, return to the surface can be accompanied by decompression sickness and air embolism. When diving in cold water, the very act of rising towards the surface can induce a scuba regulator to free flow, spilling a precious gas supply.

For pilots the sojourn can end badly on landing. This fact has been in the news lately, where seemingly inexplicable crashes occurred in large transport aircraft. I shake my head and wonder why, knowing full well that once you take a sojourn for granted, it can devour you. I also know full well that I am not immune.

I was recently reminded of that during a short 34-mile flight returning a retractable gear aircraft from maintenance back to my home base, Panama City, FL. Most pilots know that, ironically, aircraft maintenance can be risky. While maintenance on diving equipment or airplanes is certainly a critical part of safe operation, at the same time it is an opportunity for a mechanic to inadvertently damage a critical component.

Snapshot gear light
Gear lights: one light is not glowing.

I have seen a maintenance-related failure of a scuba regulator, and I was about to see it with my aircraft as I followed a business jet towards a landing at our local airport. To keep traffic flowing smoothly I kept my speed up on approach until close to the runway. When I finally slowed enough to drop the landing gear I saw two green “gear safe” lights rather than the expected three. My main gear seemed to be down and locked, but the nose wheel lock indication was not glowing that reassuring green.

“Tower, I have a problem with my gear. I need to leave the area and sort out the problem.”

I left the airport airspace and spent a full hour burning fuel, running through all emergency checklist items, pulling G’s to help the gear lock down and waiting for a Southwest Airlines flight to arrive. The local airport, which receives quite a bit of commercial jet traffic (Delta and Southwest) only has one runway. If my gear collapsed on touch-down, that single runway would have been shut down for an hour or more, and arriving flights would have to land elsewhere. There are not a lot of good alternate airports near Panama City.

The sun was getting low, and I did not want to make that landing at night. Besides, my wife was below, waiting anxiously for whatever was going to happen. She was due to pick me up at the hangar, but she and I both knew the aircraft might not make it far past the touchdown point on the runway.

After flying past the tower twice and having them inspect the gear with binoculars, the tower controller said the gear looked down, but I knew there was no way to tell if it was down and locked. If the nose gear was not locked, it would collapse on landing.

Fortunately I was alone in the cockpit so I could  come to grips with what I was about to do without the distraction of worried passengers. I announced my intentions to land, and on my last circuit of the field I saw the crash rescue truck and fire truck pulling into position along the runway. That was a sight no pilot ever wants to see.

As I turned towards the runway I reviewed the landing checklist one last time, and then I was ready. As I turned final it was time to get it over with. Whatever would happen would happen, and there was nothing more I could do about it.

Approaching the runway and ready to land, my mind was focused on only one thing — making the landing as smooth as possible.

The main wheels squeaked as they touched the concrete, ever so gently, and with steady back pressure on the yoke I kept the nose high, sparing the nose gear as long as possible as the plane slowed.


When gravity overcame the aerodynamic lift on the nose, the wheel settled to the runway — and  rolled.

My first word to the tower was, “Thank God!”

“Indeed”, they replied. They had been holding their breath as well, as they later told me.

The next day when the mechanics drove in, it only took them five minutes to adjust a tab on the nose gear down-lock switch. Such a simple fix for such a lot of drama.

The offending nose gear.

Now that I’ve had time to reflect on the incident,  I’ve come to appreciate the valor of the silver-suited firefighters who approached me after the landing, the firefighters who are prepared to thrust themselves into the flames to rescue those whose sojourns have gone awry. I was also appreciative of the calm-voiced air field controller whose only weapon against calamity was the calm tone of his voice.

Calm is a good thing when you’re trying to land a plane with all the tenderness of putting a candle on a birthday cake.


The Siren’s Call of Rebreather Oxygen Sensors

Sirens Cove (contributed by Spanish Conqueror to Mythical Mania Wiki)

In Greek mythology irresistibly seductive female creatures were believed to use enchanted singing to beckon sailors to a watery grave.

Why this myth endured through the centuries is difficult to say. However, my theory is that it helped explain to grieving widows and mothers why ships sometimes inexplicably disappeared, taking their crew with them, never to be seen again. By the reasoning of the time, there must have been some sort of feminine magic involved.

The oxygen sensors in closed-circuit, electronically or computer-controlled rebreathers are a magic device of sorts. They enable a diver to stay underwater for hours, consuming the bare minimum of oxygen required. The only thing better than a rebreather using oxygen sensors would be gills. And in case you wondered, gills for humans are quite impractical, at least for the foreseeable future. r22van

I have written, or helped write three diving accident reports where the final causal event in a rebreather accident chain proved to be faulty oxygen sensors. So for me, the Siren call of this almost magical sensor can, and has, lured divers to their seemingly blissful and quite unexpected death.

Those who use oxygen sensors know that if the sensor fails leading to a hypoxic (low oxygen) state, loss of consciousness comes without warning. If sensor failure results in a hyperoxic state (too high oxygen), seizures can occur, again leading to loss of consciousness, usually without warning. Unless a diver is using a full facemask, loss of consciousness for either reason quickly leads to drowning.

EX 19 rebreather (U.S. Navy photo)

Due to the life-critical nature of oxygen control with sensors, three sensors are typically used, and various “voting” algorithms are used to determine if all the sensors are reliable, or not. Unfortunately, this voting approach is not fail-proof, and the presence of three sensors does not guarantee “triple” redundancy.

In one rebreather accident occurring during the dawn of computer-controlled rebreathers, a Navy developed rebreather cut off the oxygen supply to a diver at the Navy Experimental Diving Unit, and all rebreather alarms failed. The diver went into full cardiopulmonary arrest caused by hypoxia. Fortunately, the NEDU medical staff saved the diver’s life, aided in part by the fact that he was in only 15 feet of water, in a pool.

In two more recent accidents the rebreathers kept feeding oxygen to the diver without his knowledge.  One case was fatal, and the other should have been but was not. Why it did not prove fatal can only be explained by the Grace of God.

The two cases were quite different. In one the diver broke a number of safety rules and began a dive with known defective equipment. He chose to assume that his oxygen sensors were in better shape than the rest of his rebreather. If he had been honest with himself, he would have realized they weren’t. If he had been honest with himself, he would still be alive.

The other dive was being run by an organization with a reputation for being extremely safety conscious. Nevertheless, errors of omission were made regarding oxygen sensors which almost cost the experienced diver his life.

In the well-documented Navy case, water from condensation formed over the oxygen sensors, causing them to malfunction. The water barrier shielded the sensors from oxygen in the breathing loop, and as the trapped oxygen on the sensor face was consumed electrochemically the sensor would indicate a declining oxygen level in the rig, regardless of what was actually happening. Depending on how the sensor voting logic operated, and the number of sensors failing, various bad things could happen.

During its accident investigation, when NEDU used a computer simulation to analyze the alarm and sensor logic, it found that if two of the three sensors were to be blocked (locked) by condensed water, the rig could lose oxygen control in either a hypoxic or hyperoxic condition. Based on a random (Monte Carlo) sensor failure simulation, low diver work loads were more often associated with hypoxia than higher work rates, even with one sensor working normally.

We deduce from this result that “triple redundancy” really isn’t.

The white circles at the top left of this scrubber canister housing are the three oxygen sensors used in an experimental U.S. Navy rebreather.

When the accident rig was tested in the prone (swimming) position at shallow depth, after 2 to 3 hours sensors started locking out, and the rig began adding oxygen continuously. The computer simulation showed that the odds of an alarm being signaled to the diver was only 50%. The diver therefore could not count on being alerted to a sensor problem.

Unfortunately in this near fatal case the rig stopped adding oxygen, the diver became hypoxic and the diver received no alarms at all.

After NEDU’s investigation, the alarm logic was rewritten with a vast improvement in reliability. The orientation of the sensors was also changed to minimize problems with condensation.

Today what is being seen are divers who extend the use of their sensors beyond the recommended replacement date. Like batteries, oxygen sensors have a shelf-life, but they also have a life dependent on use. Heavily used sensors may well be expended long before their shelf-life has expired.

The Siren, by John Williams Waterhouse.

Presumably, the birthing pains of the relatively new underwater technology based on oxygen sensors have now passed. Nevertheless, those who use rebreathers should be intimately familiar with the many ways sensors, and their electronic circuitry, can lead divers ever so gently to their grave.

Like sailors of old, there are ways for divers to resist being lulled to their death by oxygen sensors. First among them is suspicion.  When you expect to have a great day of diving, you should be suspicious that your rebreather may have different plans for you. Your responsibility to yourself, your dive buddies and your family is to make sure that the rebreather, like a Siren, does not succeed in ruining your day.


The best way to ward off sensor trouble is through education. To that end, Internet sites like the following are useful. Check with your rebreather manufacturer or instructor for additional reading material.













Margin of Safety

A diver’s breathing equipment, helmet, gas bottle, umbilicals and buoyancy compensator lie stretched out on the grey concrete floor.  The diving gear has a look of sadness about it. Perhaps that equipment will tell a story of why its owner is dead, but usually it does not.

Storm clouds from 30,000 ft. Photo by Wendell Hull.

In another part of the world the NTSB catalogs the fragments of an airplane shredded by the elements and thrown in a heap back to earth. The only good thing to come from an aircraft accident is that usually there are enough clues from wreckage, radio recordings, radar returns and weather reports to piece together a story of the end of life for pilot and passengers.

It’s always the question of “Why?” that drives any investigation.

Perhaps it is the knowing of how death comes, so unexpectedly to surprised souls, that makes it just a little bit easier to make the mental and emotional connection between an interesting moment and a deadly moment. If that is true, and I believe it is, then the telling of such macabre stories can be justified. It is not a telling through morbid interest, but a sincere belief that by examining death closely enough we can somehow force it to keep its distance.

That may be foolish thinking, but humankind seems to have a hunger for it, that esoteric knowledge, so perhaps it is a truism. Perhaps we sense instinctively that the knowing of something makes it less fearsome.

Being a student of diving and diving accidents, I know full well how unexpected events can make you question what is real and what is not, what is normal and what is abnormal. Without practiced calm and reasoning, unexpected events can induce panic, and underwater, panic often leads to death. That is also true for aviation.

The best preventative for panic is a realistic assessment of risk. Risks are additive. For instance, flying in the clouds is accompanied by a slight degree of risk, but with a properly maintained airplane, with a judicious use of backup instruments and power supplies, and with recent and effective training, that risk can be managed. In fact, I delight in flying in clouds; it is never boring, and I know that I am far safer than if I had been driving on two lane roads where the potential for death passes scant feet away every few seconds.

Flying at night is another risk. If something were to go terribly wrong, finding a safe place to land becomes a gamble. On the other hand, seeing and avoiding aircraft at night is simple because of the brilliant strobe lighting which festoons most aircraft. For me, the beauty, peace and calm air of night flight makes it well worth the slight risk.

Garmin NEXRAD Weather display.

Technology has made weather flying safer and, I have to admit, more enjoyable. The combination of GPS driven maps and NEXRAD weather has made it almost impossible to blunder into truly bad weather. During the daytime, my so-called eyeball radar helps to confirm visually what NEXRAD is painting in front of me. If it looks threatening, it probably is.

Unlike aircraft weather radar, virtually every pilot can afford to have NEXRAD weather in the cockpit. And unlike aviation radar, NEXRAD can see behind storms to show the view 100 miles downrange, or more. Having often flown in stormy weather without benefit of NEXRAD,  I truly rejoice in the benefits of that technology.

WX 900 Stormscope

I routinely fly with not only NEXRAD, but also a “Storm Scope” that shows me in real time where lightning is ionizing the sky. Those ozone-laced areas are off-limits to wise aviators. But sometimes even a Storm Scope is not enough to keep the willies, or as some call it, your spidey sense, from striking. (Presumably spiders are not particularly cerebral, but they are pretty adept at surviving, at least as a genus and species.)

I was recently flying around stormy weather, carefully avoiding the worst of it, and maneuvered into a position that would provide a straight shot home with yellow tints showing on the weather screen, suggesting at most light to moderate precipitation. I had flown that sort of weather many times; it usually held just enough rain to wet the windshield.

However, my internal risk computer made note of the following factors: we were in the clouds so if weather worsened I wouldn’t see it. Night was approaching which markedly darkened the wet skies we were beginning to enter.  The clouds and darkness conspired to make useless my eyeball radar. In addition, the Storm Scope was unusually ambiguous at that moment. I thought it was confirming a safe passage home, but I could not be 100% certain.

On top of that, the FAA recently warned that NEXRAD signals can be considerably more delayed than indicated on the weather display. The device might say the data is 2 min old, but the actual delay could be 10 minutes or more. In other words, the displayed image could be hiding the truth.

Aircraft weather radar.

Planes have been lost because of untimely NEXRAD data. For that reason there is a philosophical difference between NEXRAD and true radar. On board weather radar is said to be a tactical weather penetration aid, and NEXRAD is a strategic avoidance asset. My gut told me that at that moment in airspace and time the boundaries between those two uses, tactical and strategic, were getting fuzzy.

It is times like that when an awareness of the slim margin between a safe flight or dive, and a deadly flight or dive, becomes a survival tool. In this case, I and many other experienced pilots have made the call to turn around and land. Unfortunately, the record and the landscape is littered with the wreckage of those who chose otherwise.

They forgot just how thin the margin of safety can be.

The flight (green line) from Cobb County Regional (KRYY) to Panama City (KECP) was interrupted by a stop at Montgomery AL.









Carbon Dioxide – The Diver’s Nemesis Pt. 1 (Meduna’s Mixture)

Of all the gases humans excrete, the most bountiful, and arguably the most deadly, is exhaled carbon dioxide.

There is a forgotten bit of American medical history that reveals the bizarre features of the toxicity of carbon dioxide. In 1926, before the advent of modern psychiatric medications, some American psychiatrists began experimenting with the use of inhaled carbon dioxide for the treatment of schizophrenia and psychoses. At the time, there were no effective treatments other than electroshock.

Dr Ladislas J. Meduna

One of the most successful of these researchers was Dr Ladislas J. Meduna, a Professor of Psychiatry at the University of Illinois College of Medicine in Chicago.

High levels of carbon dioxide (CO2) did in fact have some success in treating schizophrenia, but it also produced Out of Body (OBE) and seemingly spiritual experiences. The following text is quoted from a book called Carbon Dioxide Therapy. A Neurophysiological Treatment of Nervous Disorders, published in 1950 and authored by Meduna.Meduna administered by mask between 20 and 30 breaths of a gas mixture of 30% CO2, 70% O2. From pg. 22 of his book we find,

“Any attempt to define the sensory phenomena during CO2 anesthesia, in terms of dream, hallucination, illusions, etc., would be futile. The actual material would support any hypothesis. Some of the sensory phenomena would direct us to define them as hallucinations. Some of these phenomena are felt by the patients as “real dreams”; others obviously are dreamy repetitions of real events in the past or of past dreams. I believe therefore that any classification of these phenomena in terms of dream or hallucination would be not only meaningless, but directly misleading; the patient is not “sleeping” in the physiological sense, nor is he in the state of consciousness which we usually assume to be present in true hypnagogic hallucinations.”

click to enlarge

“One subject, after 20 respirations of the gas, reported seeing a “bright light, like the sun.”

“It was a wonderful feeling. It was marvelous. I felt very light and didn’t know where I was. For a moment I thought: ‘Now isn’t that funny. I am right here and I don’t know whether I am dreaming or not.’ And then I thought that something was happening to me. This wasn’t at night. I was not dreaming. And then it felt as if there were a space of time when I knew something had happened to me and I wasn’t sure what it was. And then I felt a wonderful feeling as if I was out in space.”

“After the second breath” — reported a 29 year-old healthy female nurse who had taken a treatment – “came an onrush of color… then the colors left and I felt myself being separated; my soul drawing apart from the physical being, was drawn upward seemingly to leave the earth and to go upward where it reached a greater Spirit with Whom there was a communion, producing a  remarkable, new relaxation and deep security. Through this communion I seemed to receive assurance that the petite problems or whatever was bothering the human being that was me huddled down on the earth, would work out all right and that I had no need to worry.”

“In this spirituelle I felt the Greater Spirit even smiling indulgently upon me in my vain little efforts to carry on by myself and I pressed close the warmth and tender strength and felt assurance of enough power to overcome whatever lay ahead for me as a human being.”

Meduna summarized that preceding case by stating, “In this beautiful experience we can discern almost all the constants of the CO2 experience: (1) color; (2) geometric patterns; (3) movement; (4) doubleness of personality; and (5) divination or feelings of esoteric importance.”

Meduna went on to admit that “Not all of the sensory phenomena experienced by the patients are of celestial beauty and serenity. Some of them are horrifying beyond description.”

In 1971, Chris Lambertsen, M.D., Ph.D., from the University of Pennsylvania School of Medicine, and considered to be the father of special warfare diving by Navy SEALS, published a careful examination of the physiological consequences of the Meduna mixture. He found that inhalation of 30% CO2 in oxygen would cause unconsciousness and convulsions within 1-3 min. The precipitating event for loss of consciousness seemed to be a catastrophic increase in the acidity of the blood due to the large amount of carbonic acid produced by the CO2 inhalation. This raises the possibility that the experiences noted by Meduna were caused by pre-convulsive events within the brain.

Since then the medical community has deemed carbon dioxide “treatments” as not only dangerous but ineffective compared to modern psychiatric medication. Meduna’s mixture is no longer used.

While at the Naval Medical Research Institute, I was my own research subject in a study of the effects of rebreathing  CO2 concentrations up to 8%. That was a carbon dioxide concentration that some Navy SEALS had claimed could be tolerated without impairment.

The simplest scrubber canister in the simplest rebreather, Ocenco M20.2

I was not under water, but riding a stationary bicycle ergometer in the laboratory, simulating breathing on a closed-circuit underwater breathing apparatus (in diving vernacular, a rebreather.) Although oxygen was being added as I consumed it, there was no carbon dioxide scrubber (a container of carbon dioxide absorbing material), so the test was examining what happens when a scrubber canister is no longer functioning properly. At 7% inspired  CO2 I stopped the exercise, feeling a little abnormal. However, I was surprised at how unimpaired I seemed to be; that was, until I attempted to dismount the ergometer. I almost fell and needed help removing myself from the bicycle to a chair.

The single-minded and simple-minded task of exercising had hidden a growing central nervous system impairment. Like someone intoxicated with alcohol, I could not judge my level of impairment until a task requiring some coordination was required.

So we see that high levels of carbon dioxide intoxication can lead to profound disturbances of the central nervous system. In upcoming posts we’ll see how elevated carbon dioxide levels and the control of respiratory ventilation can interact to put rebreather divers at risk.

Much of the above is from a nonfiction book project currently under review. The working title for the book is “Collected Tales of the Spiritual and Paranormal.”


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.


Divers In Space

Signs of flowing water have been found on Mars. http://www.nytimes.com/2011/08/05/science/space/05mars.html?_r=1

That of course makes Mars even more tantalizing than it is already.

Now Mars has been added to a growing list of bodies in our solar system that are believed to have water, and in some cases entire oceans. Let me be so bold as to pronounce, where you have water, you will eventually need divers.

Biosphere 2

I once attended a joint NASA – Diving Conference at Disney World in Orlando. It was largely devoted to discussions of the science and engineering that would be required to send men and women to Mars and to sustain them in a colony. I was presenting a diving related talk at the invitation of one of the editors of the Life Support & Biosphere Science journal, a short-lived scientific journal that reported on the science conducted in Biospheres and other life-support systems.

After hearing a number of fascinating NASA accounts, I talked about a rather arcane subject: A Priori models in the testing of diving life support equipment. That work was published in 1996. At the end of the talk, a NASA engineer asked, somewhat smugly I felt, how diving had anything to do with space.

Well, that wasn’t at all the purpose of the meeting, or the reason why I was talking. The organizers believed, correctly, that sojurns in space and underwater share elements in common; namely, people and breathing equipment. We could, and should, learn from each other.

Now, regarding the question: I can ad lib with the best of them. Knowing that Jupiter’s moon Europa was believed to be hiding a large ocean beneath its icy surface, I responded that someday astronauts will be carrying a dreadfully expensive piece of hardware to an alien moon or planet with water, and that priceless tool will get dropped  — into the water. It happens all the time on Earth.

Now what? You can’t go on-line, order a replacement, and expect an overnight FedEx shipment.  That is when a space diver would be worth his Earth-weight in rhodium.

Saturn's moon Enceladus

Since that time, we’ve learned that Saturn’s moon Enceladus jets water from its south pole.  As reported in the journal Icarus, that suggests that, like Europa, there may be a liquid ocean beneath the moon’s icy crust.

My suspicion is that long before we’ll need cowboys in space, we’ll need divers in space.

So divers, keep your diving helmets oxygen clean. You may get the call any day now.

Outsmarted by an Octopus

Jim Duran and I started a night dive in about sixty to seventy feet of water several miles off the beaches of Panama City, FL. I was wearing double 80 tanks, held a collecting bag and lights, and fully intended to capture an octopus, alive.

At the time I was working in an invertebrate physiology laboratory at Florida State University, under the mentorship of Dr. Michael Greenberg. I had been impressed by the reputed high intelligence of the octopus, and was also interested in the effects of high pressure. The Navy base at Panama City had a new high pressure chamber, capable of simulating deep-sea pressures. Since I was in training in the combined Navy and NOAA program called the Scientist in the Sea, it seemed logical to me to catch an octopus, and study it to see if it would be a suitable candidate for testing in the Navy’s  giant hyperbaric chamber.

It sounded like a reasonable plan to me, and Jim Duran was willing to follow along as my assistant critter catcher. And to begin with, the plan worked. We spied our quarry only a few minutes into the dive. The gray-brown octopus was crawling over the sandy bottom, and initially seemed unaware of our intentions. But as the two of us closed in on him, specimen bag flapping in our self-generated current, he sprang off the bottom and squirted away.

But we were strong swimmers, and our quarry was in the open, maybe eight feet off the bottom. He had nowhere to hide – silly thing. Keeping our lights on him, and stroking like mad, I began gaining on him, at which time he let loose with his ink. I was prepared for that, and continuing to kick I soon caught up with him and got my hands on him, trying to stuff him into my bag. But he would have none of that.

Off we went again. What we didn’t realize was that the clever invertebrate was constantly turning to our right. We of course were too intent on capturing him to notice his strategy. And besides, invertebrates were incapable of strategic planning – or so we thought.

Apparently the octopus was determined not to be touched again, or else we were tiring, for we never quite caught up with him. So close, and yet so far away.

And then a curious thing happened. He collapsed his tentacles upon themselves, streamlining his body shape, and shot like a rocket from our depth to the sandy bottom. Once on firm ground again, he spread his tentacles as wide as he could, and his entire body turned white. I froze in shock.

In another instant, before I could recover my senses, he collapsed his body down to the width of an apple and slithered into his hole in the sea floor.

He was gone.

It didn’t take long for us to realize that the chase had started near his home, and he had led us at a furious pace in a large circle, which ended precisely where it had begun. He had maneuvered us to within striking distance of safety.

Humbled, and now growing low on air, and embarrassingly empty-handed, we headed back to the off-shore platform where our dive had begun.

It had seemed like such a good idea. Who knew that two graduate students would be outsmarted by an invertebrate.

Below is a link to a video showing an octopus’ ability to disguise itself, and some of the defensive behavior we witnessed.

[youtube id=”PmDTtkZlMwM” w=”500″ h=”400″]

My Top Three Diving Sites: The Red Sea Pt. 2

I was one little inch away from BIG trouble.

Twenty kilometers north of Sharm el-Sheik are four current-swept reefs that attract Red Sea divers and bountiful sea-life alike. We left for the dive site from Ras Nasrani, heading for Thomas Reef, in the middle of the current-swept Straits of Tiran.

Thomas Reef is the smallest but most popular reef for diving. Because of the current, it requires a different diving technique than the simple but awe-inspiring wall dives at Ras Mohammed. Our dive boat with some diving professionals and tourists onboard anchored just off  Thomas Reef  and quickly had its bow swept into the current.

The plan was to enter the water from the stern, and follow the anchor line down to a point where we could kick like mad and make our way to coral encrusted rocks. From there, it would be a fairly short swim against the current, using the rocks for assistance, until we entered the calm water in the lee of the reef.

Thomas Reef provides a unique dive site due to the sea life attracted to the current. Because of that, it is well worth negotiating the heavy flow; rewards awaited the determined diver. In my case, a surprise awaited me as well.

As I let loose of the anchor chain, I could clearly see the steeply sloping bottom features of the reef, where I was headed. I spotted my target rock and kicked mightily until it was in my grasp. Now anchored, I had time to survey the beauty around me, and plan my next step. It was then that I noticed that an inch way from my naked right hand, the one firmly grasping the rock, sat not just another stone, but a stone with eyes.

It was in fact, something far more dangerous than a stone —  it was a stonefish.

Red Sea Stonefish

Stonefish are reputed to be the most venomous fish in the world. Had I grabbed it instead of its stony neighbor, glands at the base of its many dorsal spines would have flooded my bare hand with venom. The sting causes intense pain; with the affected body part swelling rapidly, potentially leading to death of tissues.

Just how bad the symptoms become depends on the anatomical location of the punctures, depth of penetration and the number of spines involved. The effects of the venom are muscle weakness, temporary paralysis and shock, which, if encountered during a scuba dive in a strong current, could make a safe return to the dive boat somewhat  difficult. If not treated, the incident could prove fatal.

The emergency treatment required is  much more than is likely to have been available on a chartered dive boat. As breathtaking as a Red Seas trip promises to be, you might stumble across critters that can take your breath away, literally. So a check of the closest and most capable medical facility should be high on your pre-dive checklist.

No doubt about it, if I had grabbed the wrong “stone” I would have been in a world of hurt; and probably in a lot of trouble with my dive buddies as well since that trip would have been brought to a sudden and exciting conclusion.

Oh yeah, once I overcame my surprise, and moved on, ever so carefully to the lee of the island-like reef, the experience was everything I had come to expect from the Red Sea.

Highly recommended!

My Top Three Diving Sites: The Red Sea, Sharm el-Sheik

I’ve read a couple of books lately where the author, critically injured in an accident, experiences what seems to be a visit to heaven, followed by a swift return to Earth.  The most recent such book was Flight to Heaven, by CAPT Dale Black, a plane crash survivor.

A common theme in these books is that the author finds colors in Heaven to be much purer and vibrant than any colors seen on Earth. Well, I know a place just like that, and for a diver it must indeed be heaven on Earth. It’s called the Red Sea.

Sharm el-Sheik and Ras Muhammad are located on the southern tip of the Sinai Peninsula, where the Gulf of Suez and the Gulf of Aqaba meet the Red Sea. On my first dive at Ras Mohammed, as I sank below the water’s surface I saw a wall of color that defied description. The phrase, “a riot of color”, is a cliché, but that is what I saw. It was as if every inch of the reef was shouting for attention, clamoring to be the most colorful, the most interesting piece of rock ever created. I was stunned — in sensory overload from the beginning to the end of that dive.

At Ras Muhammad, the coral encrusted wall dropped at a dizzying angle, headed for depths of 3000 feet, 1000 m, a very short distance from shore. I had planned a dive to no more than sixty feet, where the natural light was bright enough to show off the colors cascading downward, towards what seemed to be a bottomless abyss. But at sixty feet I saw a never ending waterfall of fauna, just a few feet below me, and then below that, even more. The colors were still spectacular even at that depth, defying all the laws of physics as I understood them.

When I realized I was twenty feet below my planned dive depth, a curious thing happened. I stopped searching for the next most beautiful thing, stopped my descent, but for a few moments I had an almost overwhelming desire to throw rational thought aside and continue down into the abyss.

I understood the consequences of that action, had I continued deeper, but the experience in that moment seemed to transcend my worth as a human being. The living communal organism, and all the life forms sustained by it, clutching close to the wall, seemed to have much greater significance in the whole scheme of things than I did. I felt a kinship, perhaps pointing to our theorized evolutionary beginnings, that made it seem that where I was, was where I belonged.

Napolean Wrasse - Egypt. (Photo credit - Sami Salmenkivi.)

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.