How Will You Try to Kill Me?

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Émile Jean-Horace Vernet-The Angel of Death

It’s been over three years since I posted a cautionary tale about oxygen sensors in rebreathers, and the calamities they can cause. Since then, the toll of divers lured to their death has been steadily mounting. In one week alone in April 2016, at almost the same geographical latitude in Northern Florida, there were two diving fatalities involving rebreathers. It is an alarming and continuing trend.

I know a highly experienced diver who starts each dive by looking at his diving equipment, his underwater life support system, and asking it that title question: How will you try to kill me today?

This deep cave diver, equally at home with open circuit scuba and electronic rebreathers, is not a bold cave diver. He is exceptionally cautious, because he is also the U.S. Navy’s diving accident investigator. He has promised me that his diving equipment will never end up in our accident equipment cage.

He and I have seen far too many of the diving follies where underwater life support systems fail their divers. But the crucible in which those fatal failures are often born are errors of commission or omission by the deceased.

Carelessness and an attitude of “it can’t happen to me” seem all too prevalent, even among the best trained divers. Divers are human, and humans make mistakes. Statistically, those accidents happen across all lines of experience: from novice divers, to experienced professional and governmental divers, and even military divers. They all make mistakes that can, and often do, prove fatal.

It is exceedingly rare that a life support system fails all by itself, since by design they are robust, and have either simple, fool-proof designs, or redundancy. In theory a single failure should not bring a diver to his end.

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The “head”, triplicate oxygen sensors, oxygen solenoid and wiring leading to the rebreather CPU. Image from jj-ccr.com.

 

Are oxygen sensors trying to kill you? That depends on how old they are? Are they in date? Ignoring the expiration date on chocolate chip cookies probably won’t kill you, but ignoring the expiration date on oxygen sensors may well prove fatal. Complex systems like rebreathers depend upon critical subsystems that cannot be neglected without placing the diver at risk.

Oxygen sensors are usually found in triplicate, but if one or more are going bad during a dive, the diver and the rebreather can receive false warnings of oxygen content in the gas being breathed.  We have seen a rebreather computer “black box” record two sensor failures, and it’s CPU logic deduced that the single working sensor was the one in error.

The controller’s programmed logic forced it to ignore the good sensor, and thus the controller continued to open the oxygen solenoid and add oxygen in an attempt to make the two dying sensors read an appropriately high O2. Eventually, the diver, ignoring or not understanding various alarms he was being given, went unconscious due to an oxygen-induced seizure. His oxygen level was too high, not too low.

Unlike fuel for a car or airplane, you can have too much oxygen.

Oxygen sensors do not fail high, but they do fail low, due to age. Rebreather manufacturers should add that fact into their decision logic tree before triggering inaccurate alarms. But ultimately, it’s the diver’s responsibility to examine his own oxygen sensor readings and figure out what is happening. The analytical capability of the human brain should far exceed the capability of the rebreather CPU, at least for the foreseeable future.

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JAKSA high pressure 6-volt solenoid used in a Megalodon rebreather. NEDU photo.

Oxygen addition solenoids hold back the flow of oxygen from a rebreather oxygen bottle until a voltage pulse from the rebreather controller signals it to open momentarily. The oxygen flow path is normally kept closed by a spring inside the solenoid, holding a plunger down against its seat.

But solenoids can fail on occasion, which means they will not provide life giving oxygen to the diver. The diver must then either manually add oxygen using an addition valve, or switch to bailout gas appropriate for the depth.

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Cut-away diagram of a 24-volt Jaksa 200 bar solenoid.

Through either accident or design, divers have been known to invert their solenoid spring and plunger, thereby keeping the gas flow open. In that case, oxygen could not be controlled except by manually turning on and off the valve to the oxygen tank. Of course, knowing when oxygen is too low or too high would depend upon readings from the oxygen sensors.

Suffice it to say that such action would be extremely reckless. And if the oxygen sensors were old, and thus reading lower than the true oxygen partial pressure, the diver would be setting himself up for a fatal oxygen seizure. It has happened.

Assuming a solenoid has not been tampered with, alarms should warn the diver that either the solenoid has failed, or that the partial pressure of oxygen is dropping below tolerance limits.

But as the following figures reveal, if the diver does not react quickly enough to add oxygen manually, or switch to bail out gas, they might not make it to the surface.

The three figures below are screen captures from U.S. Navy software written by this author, that models various types of underwater breathing apparatus, rebreathers and scuba. In the setup of the model, an electronically controlled, constant PO2 rebreather is selected. In the next screen various rebreather parameters are selected, and in this case we model a very small oxygen bottle, simulating an oxygen solenoid failure during a dive. On another screen, a 60 feet sea water for 60 minutes dive is planned, with the swimming diver’s average oxygen consumption rate set at 1.5 standard liters per minute.

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On the large screen shot below, we see a black line representing diver depth as a function of time (increasing from the dashed grey line marked 0, to 60 fsw), a gray band of diver mouth pressure, and an all-important blue line showing the partial pressure of inspired oxygen as it initially increases as the diver descends, then overshoots, and finally settles off at the predetermined control level of oxygen partial pressure (in this case 1.3 atmospheres). Broken lines on the very bottom of the graph show automated activation of diluent add valve, oxygen add solenoid, and over pressure relief valve. Long horizontal colored dashes show critical levels of oxygen partial pressure, normal oxygen level (cyan) and the limit of consciousness (red).

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Screen shot of UBASim results after an ill-fated 60 fsw dive.

The oxygen solenoid fails 53.7 minutes into the dive, no longer adding oxygen. Therefore the diver’s inhaled oxygen level begins to drop. Rather than follow the emergency procedures, or perhaps being oblivious to the emergency, this simulated diver begins an ascent. As ambient pressure drops during the ascent, the drop in oxygen pressure increases.

In this particular example, 62.5 minutes after the dive began, and at a depth of 13.5 feet, the diver loses consciousness. With the loss of consciousness, the diver’s survival depends on many variables; whether he’s wearing a full face mask, whether he sinks or continues to ascend, or is rescued immediately by an attentive boat crew or buddy diver. It’s a crap shoot.

So basically, the rebreather tried to kill the diver, but he would only die if he ignored repeated warnings and neglected emergency procedures.

What about your rebreather’s carbon dioxide scrubber canister? Do you know what the canister duration will be in cold water at high work rates? Do you really know, or are you and the manufacturer guessing? What about the effect of depth, or helium or trimix gas mixes? Where is the data upon which you are betting your life, and how was it acquired?

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Scrubber canister and sodalime. NEDU Photo
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NEDU photo.

 

 

 

 

 

 

 

 

 

 

 

Sadly, few rebreathers have dependable and well calibrated carbon dioxide sensors; which is unfortunate because a depleted or “broken through” scrubber canister can kill you just as dead as a lack of oxygen. The only difference is a matter of speed; carbon dioxide will knock you out relatively slowly, compared to a lack of oxygen.

But if you think coming up from a dive with a headache is normal, then maybe you should rethink that. It could be that your rebreather is trying to kill you.

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Samael_(Angel_of_Death)

 

 

 


Where Things Move Quickly and Darkly

I came across a great article from the New Yorker with an interesting title. In fact, my interest lasted all the way to the end.

Spooked: What do we learn about science from a controversy in physics?

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“Albert Einstein (Nobel)” by Unknown – Official 1921 Nobel Prize in Physics photograph. Licensed under Public Domain via Wikimedia Commons

If you get the feeling that science is not as pure of thought and logic as it pretends to be, then you will find some comfort in Adam Gopnik’s approachable review of the deeply hidden controversy surrounding what Albert Einstein called “spooky action at a distance.” Spooky action is the weirdest of all science, and makes telepathy and clairvoyance seem almost banal by comparison.

In my opinion, parts of Gopnik’s none-too-technical article remind me of the quote by Dr. Jason Parker, the protagonist in the science fiction thriller, “Middle Waters“. In a supposed speech to the open-minded Emerald Path Society, Parker said, “There are regions between heaven and Earth where magic seems real and reality blurs with the surreal. It is a place where things move quickly and darkly, be they friend or foe. The hard part for me is knowing the difference between them.”

Gopnik expressed that thought more prosaically by the following: “”Magical” explanations, like spooky action, are constantly being revived and rebuffed, until, at last, they are reinterpreted and accepted. Instead of a neat line between science and magic, then, we see a jumpy, shifting boundary that keeps getting redrawn.”

Gopnik goes on to say, “Real-world demarcations between science and magic … are … made on the move and as much a trap as a teaching aid.”

To be honest, I did leave out Gopnik’s entertaining reference to Bugs Bunny and Yosemite Sam. Again, if you have ever been suspicious of the purity of science, the New Yorker article is well worth the read.

Unlike the concerns of Einstein, Neils Bohr and the rest of the cast of early 20th century physicists, the anxiety of Jason Parker, the fictional hero, is not cosmological; it’s personal. It’s every bit as personal as it is for each of us when we sometimes question our sanity.

Yes, real life can be like that sometimes, when things intrude into our ordered lives, as quickly as a Midwest tornado, but with less fanfare and warning. But every bit as destructive. And it is at those points, those juxtapositions with things radical, unexpected, that we end up questioning our grip on reality.

After all, what could be more unexpected and unreal seeming than the notion that cosmological matter we can’t see, dark matter, could send comets crashing into the Earth, as Gopnik mentioned, and the  Harvard theoretical physicist Lisa Randall wrote about in her book Dark Matter and the Dinosaurs.

So, Jason Parker had every reason to be wary of things that move quickly and darkly. They can be a killer.

Sometimes, as in the case of Parker, those internal reflections do end up having a cosmological consequence. But even if they don’t, it’s a good idea to occasionally reexamine our lives for the things which may seem one day to be magical, and the next day to be very real.

In short, the magic should not be dismissed out of hand, because, after all, just like “spooky action at a distance” and “dark matter”, it may not be magic after all.

 

 

Remote Viewing – Stretching the Limits of Science in Fiction

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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.

 

 

Eating Crow – Safe Water Temperatures for Scuba Regulators

CrowScientists and engineers love to argue, and unlike the case with politicians, compromise is not an option. Technologists speak for nature, for the truth of a universe which does not speak for itself. But when a technologist is wrong, they usually have to eat some crow, so to speak.

Stephen Hawkings, the famous cosmologist, freely admits his brilliant doctoral dissertation was wrong. Crow was eaten, and Hawkings moved on to a better, arguably more correct view of the universe.

Now, on a much less grand scale, this is my time for eating crow.

There has been quiet disagreement over the water temperature above which a scuba regulator is safe from free-flowing or icing up. Those untoward icing events either give the diver too much gas, or not enough. Neither event is good.

Based upon an apocryphal Canadian government study that I can’t seem to put my hands on anymore (government studies are rarely openly available), it has long been believed by the Canadians and Americans that in water temperatures of 38°F or above, regulator icing problems are unlikely. That temperature was selected because when testing older, low flow Canadian regulators, temperatures inside the regulator rarely dropped below 32°F when water temperature was 38°F.

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U.S. Navy photo.

As shown in an earlier blog post, in 42°F water and at high scuba bottle pressures (2500 psi) in instrumented second stage regulators (Sherwood Maximus) second stage internal temperature dropped below zero Celsius (32°F) during inspiration. During exhalation the temperature rose much higher, and the average measured temperature was above freezing. Nevertheless, that regulator free flowed at 40 minutes due to ice accumulation.

Presumably, a completely “safe” water temperature would have to be warmer than 42°F. But how much warmer?

My European colleagues have stated for a while that cold water regulator problems were possible at any temperature below 10°C, or 50°F. However, as far as I can tell that assertion was not based on experimental data. So as we began to search for the dividing line between safe and unsafe water temperatures in another brand of regulator, I assumed we’d find a safe temperature cooler than 50°F. For that analysis, we used a generic Brand X regulator.

To make a long story short, I was wrong.

To understand our analysis, you must first realize that scuba regulator freeze-up is a probabilistic event.  It cannot be predicted with certainty. Risk factors for an icing event are diving depth, scuba bottle pressure, ventilation (flow) rate, regulator design, and time. In engineering terms, mass and heat transfer flow rates, time and chance determine the outcome of a dive in cold water.

At NEDU, a regulator is tested at maximum anticipated depth and ventilated at a high flow rate (62.5 L/min) for a total period of 30 min. If the regulator free flows or stops flowing, an event is recorded and the time of the event is noted. Admittedly, the NEDU test is extremely rigorous, but it’s been used to select safe regulators for U.S. military use for years.

Tests were conducted at 38, 42, 45 and 50°F.

Next, an ordinal ranking of the performance for each regulator configuration and temperature combination was possible using an NEDU-defined probability-of-failure test statistic (Pf). This test statistic combines the number of tests of a specific configuration and temperature conducted and the elapsed time before freezing events occurred. Ordinal ranks were calculated using equation 1, Eqnwhere n is the number of dives conducted, E is a binary event defined as 0 if there is no freezing event and 1 if a freezing event occurs, t is the elapsed time to the freezing event from the start of the test (minutes), and k is an empirically determined constant equal to 0.3 and determined to provide reasonable probabilities, i is the index of summation.

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Click for a larger image.

Each data point in the graph to the left represents the average result from 5 regulators, with each test of 30-min or more duration. For conditions where no freezing events were observed at 30 min, additional dives were made for a 60-min duration.

As depicted, 40-regulator tests were completed, using 20 tests of the five primary second stages and 20 octopus or “secondary” second stages. Regression lines were computed for each data set. Interestingly, those lines proved to be parallel.

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A second stage of a typical scuba regulator. The bite block is in the diver’s mouth.

The “octopus” second stage regulator (the part going in a scuba diver’s mouth) differed from the primary only by the spring tension holding the regulator’s poppet valve shut. More negative mouth pressure is required to pull the valve open to get air than in the primary regulator.

The test statistic does not provide the probability that a given test article or regulator configuration will experience a freezing event at a given temperature. However, it does provide the ability to rank the freezing event performance of regulator configurations at various temperatures.

Our testing reveals that in spite of my predictions to the contrary, for the Brand X regulator our best estimate of a “safe” water temperature, defined as Pf = 0, is roughly 53°F for the standard or “primary” second stage regulator and 49° F for the octopus or secondary regulator.

For all practical purposes, the European convention of 50°F (10°C) is close enough.

Eating crow is not so bad. Some think it tastes a little like chicken.

Separator smallEquation 1 came from J.R. Clarke and M. Rainone, Evaluation of Sherwood Scuba Regulators for use in Cold Water, NEDU Technical Report 9-95, July 1995.

Diving a Rebreather in Frigid Water: Canister Concerns

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As evidenced by Under the Pole diving expeditions, rebreathers are being used in some of the most isolated and frigid places in the world. Some of those dive missions are surprisingly deep (111 meters, 330 feet) and long, about 2 hours.

That gives me cause for pause.

I suspect most divers are aware of the 1/3 rule for gas consumption on an open circuit (scuba) cave dive. You should use no more than 1/3 of your air supply on the way in, leaving you with 1/3 for the trip out, and 1/3 of your gas supply available in reserve. Sadly, even that amount of reserve has not saved all cave divers.

Now that cave divers are using rebreathers, the rules, at least for some, have changed. Some savvy rebreather cave divers use the rule of doubles: Always have twice as much oxygen, twice as much diluent, and twice as much canister as you think you’ll need. That plus an open-circuit or semi-closed circuit bailout should keep you safe — in theory.

Gas supply is easy to measure throughout a dive; there is a pressure gauge for all gases. But what about canister duration? Most divers assume they will have more canister duration available than gas supply; which means they don’t need to worry about canister duration. That would be a good thing, if it were true. After all, how many manufacturers provide expected canister durations for various work rates and water temperatures? Maybe, none? Or certainly very few.

I would be very surprised if manufacturers could say with certainty that during a two hour dive in -2°C (28°F) water, at depths to 111 meters that the scrubber can provide double the duration needed. That would be four hours in -2°C water, at all potential diver work rates.

Some of you may say, “Under-the-ice-diving is not like cave diving, so the doubles rule is too conservative.” I invite you to think again. Under polar ice, is there ready access to the surface? Not unless you’re diving directly under the through-ice bore hole the entire time.

In the U.S. Navy experience, obtaining useful data on canister durations from manufacturers is difficult. Duration data as a function of temperature is practically nonexistent. Therefore I will share the following information gleamed from scrubber canister testing in extreme environments by the Navy. While this blogger cannot reveal canister durations for military rebreathers, the information on the coefficient of varation (COV) is not protected. (There is no way to figure out what a canister duration is based solely on the COV.)

The following 4-minute video gives a good introduction to the coefficient of variation.

https://youtu.be/XXngxFm_d5c://

All rebreather divers should know that canister performance declines in an accelerating manner as water temperature drops between 50°F and 28°F. But what your rebreather manufacturer may not know is that the innate variability of canister durations also increases as water temperature drops. The Navy has found that trend in all types of rebreathers.

So, while canister durations drop considerably in cold water, you’re also less certain about what your canister’s endurance is going to be, because of the increase in duration variability. When canister duration drops and variability increases, a diver’s margin of safety becomes a gamble. Personally, I don’t like to gamble under water.

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Coefficient of variation (COV, mean duration divided by the standard deviation) of a typical rebreather. Each data point is the mean of five canisters (n=5).

In the U.S. Navy, published canister durations take into account mean canister performance, and variability. That is accomplished through the use of 95% prediction intervals. The greater the variability in canister duration, the lower the published duration.

This method of determining safe canister durations has been in use by the U.S. Navy since 1999. However, I do not know if manufacturers use similar statistically-based methods for publishing canister durations. If they or you do not take duration variability into account as you dive cold, you may be in for a shock. Due to the nature of statistics, you may have 9 deep, cold dives with no CO2 problems, but find yourself in bad shape on the 10th dive.

If you did have a CO2 problem, it wouldn’t necessarily be anyone’s fault: it could just be a result of canister variability in action.

So, diver beware. Give yourself plenty of leeway in planning rebreather dives in frigid waters. After all, you do not want to become a statistic, caused ironically by statistics.

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If you have an interest in understanding the derivation of the prediction interval equation and its application, two videos of lectures by Dr. Simcha Pollack from St. John’s University may be helpful. Part I is found here, and Part 2 is found here.

Thanks to Gene Hobbs and the Rubicon Foundation, NEDU’s original report on the use of prediction limits to establish published canister durations is found here.