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A Conversation with a Cloud

I lay on the summer grass with a young lady friend of mine. We were holding hands affectionately, talking softly about nature, love, and a future that was fated never to happen. As we talked about nothing of lasting importance, I pointed to a dying cloud. All of the clouds drifting lazily overhead were dying as the day’s heat was dissipating and the air was becoming calm, preparing for evening.

I suspect it’s an infrequent event when someone points out an act of nature that had always been visible, but had never been noticed. Indeed, we watched, not saying a word, as the first of the day’s puffy clouds ceased to exist.

I was pleased with myself; glad that my prediction had been proven true, and pleased with her reaction. In fact, I was so pleased that I still remember that incident, many years later, even though the face of the girl has mercifully faded from my memory.

However, now that I have matured enough to ponder the imponderables of life, I realize there is more to the story. As I replay the event in my mind I realize that the cloud talked back to me.

I know that sounds bizarre, but all I can say is that my memories, perhaps having been repressed due to their strangeness, are finding their way back into my consciousness. Perhaps there’s a reason for their reappearance at this stage in my life.

I am not dying; the cloud closest to me seemed to be saying.

I was at first taken aback. After all, who’s ever heard a cloud speak.

I said I am not dying.

OK, if a cloud is willing to talk to me, I suppose I should respond. That would only be polite.

“Yes you are,” I argued, politely of course. “You’re getting thinner by the minute. In fact, you’re disappearing before my eyes.”

I’m not dying; I’m resting.

I laughed, with Monty Python’s Dead Parrot sketch in my mind.

“Well, resting or not, you’re quickly disappearing.”

But I’m still here.

“You’ll be long gone, any minute now.”

I am moisture; water vapor. That will still exist. It just won’t be visible to you.

“But your whiteness, your cloud, what you are, will be gone.”

I am not a cloud. I am moisture. A cloud is my physical appearance, but that changes throughout my life. And regardless of how I look, what I am, vapor, still exists.

“Well, you’re looking very anemic now.”

I am not anemic!

Apparently the fading cloud had feelings, and perhaps a little bit of a temper.

“Well, you are at least looking very benign right now.”

Like I said, I am resting. Today my mission is to provide shade. Today is an easy life for me.

“So, does that mean you’ll be reborn tomorrow?”

Of course.

“And you’ll look different?”

No two clouds are ever alike.

Strangely, I was beginning to understand that cloud, just a little perhaps, through some seemingly impossible way. And then I had an uncharacteristically profound thought, for a young man.

“You say the true you is nothing more than water vapor. Would you call that your soul?”

By now the cloud had completely disappeared, but I could still hear its voice in my head.

It is what I am. It is always there; it does not change. If that is what you call a soul, then so be it.

By now the voice of that thing that used to be a cloud was fading as the invisible vapor moved on.

Needless to say, I did not discuss what I was hearing with my then girlfriend. She moved on to another boy soon enough.

The next day dawned with building cumulus. There was instability in the air, and clouds were pregnant with moisture. Wishing for confirmation of what had happened the day before, I turned my attention to the nearest cloud.

“You look full of life this morning.”

I heard nothing.

I tried again, “You look very full of life this morning.”

You talkin to me boy? The cloud was growing vertically as well as horizontally.

“Well, I was trying to.”

Yes, I thought I heard you thinking I was pregnant.

I sincerely hoped that no one else could hear this … uh… conversation, if you could call it that.

You’re right, though. I’m about to give birth.

“To rain?” I wondered out loud.

Rain? Oh no. That’s the process, but not what is borne.

“I don’t understand”.

I give birth to puddles, ponds, lakes and oceans; any container that my rain falls into.

“Containers? Really?”

Tell me little man, do you have a mind?

I laughed. “Last time I checked. What a strange thing for a cloud to ask.”

OK, then where is it?

“In my head of course. In my brain.”

Oh you silly little man.

“What?”

Your brain is the container. Your mind is shaped by the container, but it is not the container.

It seemed very strange getting a lesson — well, maybe I could charitably call it a philosophy lesson — from a cloud. But then they tell me all knowledge is being stored in clouds. I wonder if this is what they mean.

Pay attention. I’m telling you important stuff here.

“I’m sorry; my mind was wandering.”

Minds do that. They don’t like being kept in containers; it’s too confining.

“Do tell.”

Do you know your mind survives even when your brain does not? Your mind can leave its container just like my water can leave its containers.

This was beginning to sound suspiciously like the ancient mind-body problem. Is the mind the brain, or vice versa?

Except that could not possibly be. After all, I was talking to a — cloud.

“So if we have a soul, you’re saying our soul retains its mind?”

You like that word, “Soul”. You used it yesterday.

“How do you know that?”

If you can believe it, that cloud chuckled, in a vaporous sort of way… I swear it did.

All information is shared in the clouds. That’s why I’m talking to you.

But to answer your question, yes. Your soul retains its mind. Actually, humans have been taught this for thousands of years. Yet most of them still don’t seem to understand. Which puzzles me — it’s really not that difficult.

“You know, I hate to be skeptical, but you seem way too smart for a cloud.”

Oh come now, do you really think clouds can talk?

For some inexplicable reason I was shocked by that question. Apparently I had already suspended disbelief as this second day’s conversation had become more and more interesting.

Having been forced back to reality, I answered. “Well … no. Not really.”

They’re a parable. It’s Me whose talking to you.

“Me who?”

There was no answer. I asked again, “Me who?”

That question has never been answered.

My Respiratory System is So Embarrassed

stk85284cor — Royalty free image from Punchstock.com

“Respiratory embarrassment” is an uncommon phrase most likely spoken by physicians and physiologists.

This week I found myself telling an engineer that “respiratory embarrassment can lead to an untoward event”. It quickly became apparent from the puzzled stare I received that I was not communicating.

Scientists and some medical personnel tend to do that; fail to communicate. In fact, they do it a lot.

What I was really saying is that in the right circumstances a person could have difficulty breathing, and that difficulty could cause something bad to happen; an “untoward” event. That bad thing would not necessarily be an aircraft crash, or in the case of a diver, a drowning, but it would mean that the pilot’s or diver’s performance would be impaired.

Why didn’t I just say so?

Laziness I suppose. I was using the language clinicians and physiologists are taught in graduate or medical school, and it flows out of our mouths naturally, without effort. Translating those same words into laymen’s terms takes time and effort.

I next started talking about respiratory impedance, a term understood by some but not all engineers, and rarely if ever by laymen. So once again I was not communicating well with all of my audience which was composed mostly of engineers, but not entirely.

That was the case until I used pictures to explain the otherwise difficult concepts of respiratory impedance and physiological embarrassment. The images below seemed to work, so I thought it worthwhile to share those images with you.

For you engineers, respiratory impedance is proportional to the sum of respiratory flow resistance and pulmonary and chest wall elastance.

pb-110104-buried-shulman_photoblog900 — From Shulman photoblog.

So what is that?

Well, for elastance, at least chest wall elastance, think of being buried to your neck in sand. Breathing difficulty comes from the difficulty of moving your chest wall in and out with the weight of sand pressing in on all sides. The pressure of sand impedes your breathing, hence elasticity (the inverse of compliance) is a major component of respiratory impedance.

Based on the photo of the young man pictured on the right, being partly buried for supposedly therapeutic reasons is not a pleasant experience.

Some might disagree. The man on the left is an actor in the 2008 French short film Le Tonneau des Danaïdes by David Guiraud, who seems quite at ease impeding his breathing for the sake of art. I’m guessing he’s either very dedicated, or very well paid.

In diving, respiratory elastance can be elevated by tight fitting wet suits; in aviators by tight fitting chest pressure garments, and in patients, by pulmonary fibrosis brought about by, for example, asbestos exposure.

Another key component of respiratory impedance, that thing that causes respiratory embarrassment, is flow resistance. Sticking your head in the sand would certainly be one way of generating

head-in-sand — *This image is found randomly throughout the web without attribution. The original source is unknown.*

severe respiratory resistance, with its attendant embarrassment.

out-of-breath-286x300 — From news.menshealth.com

Clinically, there are far more common sources of respiratory resistance, for example the narrowing of air passages in the lung caused by asthma. (Sticking your head in sand is probably a reasonable analogy to the sensations experienced during an asthma attack.) Chronic obstructive pulmonary disease (COPD) can also lead to a significant increase in respiratory resistance.

When you focus on the human respiratory system, the body parts shown in pink below, keep in mind that breathing can be impaired by things occurring inside the body (like asthma, COPD, fibrosis) or outside the body. Any life support system used for aviation, diving, mining, or firefighting imposes an impedance on breathing. That impedance in turn can lead to breathing difficulty, which can result in a failure to complete assigned duties.

Perhaps that’s where the “embarrassment” part comes in.

Created on www.biodigitalhuman.com ©2012.

On the Wrong Side of the Berlin Wall

It was the time of Gorbachev and Détente; an uneasy and foolish Détente if you asked a certain Russian officer, which I did as we rode from the GKSS-GUSI deep diving facility in Geesthacht, Germany back into town. It was June 1990. The Russian did not know English, and I didn’t know Russian, but the German driver understood my English enough to translate for the Russian. Gorbachev must have been out of his mind, that officer said.

A short time later a Naval Officer scientist and two technicians on my team from Bethesda, Md left Lüneburg, where we were staying, and headed to Berlin for the weekend. After an extended rainy period, the weather was finally gorgeous, and we soon found ourselves at the dividing line between East and West Berlin, surrounded by East Germany. That line, marked by the Berlin Wall, was a stark reminder of the red curtain that lay scant yards away from us.

It was an exciting time, because the Wall had already been breached the previous November, and visitors and townspeople alike were chipping away at the hard concrete, trying to eradicate the Wall and scavenge historical souvenirs.

We were no exception, although that is not what we had planned. This was simply an opportunity too good to pass.

Another opportunity appeared as a break in the line at the Brandenburg Gate. Police were allowing people to cross over into East Germany, without restraint, apparently.

While others in my team were picking away at the stubbornly dense concrete of the Berlin Wall, the young Naval Officer in civilian clothes and I sized up the situation and decided that since Détente was running at fever pitch we might as well get a glimpse of the wrong side of the Iron Curtain before it changed forever. The Germans waiting in line to cross over were excited about their newfound freedom and encouraged us to join them. “No problem,” is what they said.

There is something about those two words that always seems ironic, in retrospect.

So, with no formality at all we found ourselves walking down almost deserted streets on the other side of the Brandenburg Gate, on the Soviet side of the Berlin Wall, walking past depressingly gray buildings, with the only color being a red Aeroflot sign on a travel agency. From the looks of it, no East Germans were traveling that day.

It did not take long for the novelty of our new geographical freedom to wear off, and so we returned to the casual opening through which we entered the forbidden zone.

The only problem was, the guards wouldn’t let us back through.

Well, that was unexpected.

I suppose our dismay was obvious to the guards who knew just enough English to be dismissive, and the young Naval Officer must have had visions of his career coming to a swift and inglorious end, probably in some East German prison. I, however, am an optimist, and when the security guard muttered something in German about Check Point Charlie (I had heard of it before from some spy movie or other), we set off to rescue ourselves from our accidental confinement.

Check Point Charlie was only about two kilometers away, but a very tense two kilometers. The East German gray buildings took on a somber hue as we passed — not like battleship gray, but more like prison gray; Soviet prison gray.

I’m not sure what my Naval Officer friend was thinking during that walk, but since I had led him into this tight situation his thoughts might have bordered on the murderous.

On arrival at the East Berlin side of Checkpoint Charlie, we could clearly see the American side, which beckoned just a short distance away. But, first, we had to negotiate our way past an East German border guard.

That guard, whose uniform bore alien-looking DDR patches, frowned deeply when examining our “papers.” We did not have a visa for entry to East Germany. We clearly did not belong in East Berlin.

So close to the freedom of the American Sector, and yet so far away.

“You will have to pay.”

Mind you, the word “pay” can have many meanings, most of them neither easy nor pleasant.

Hoping with my usual optimism that he meant paying with money, I next asked, “How much?”

Looking at the American Sector from the East German side of Checkpoint Charlie.

“Five Deutschmarks.”

We had Deutschmarks, but they were West German DMs. “Not a problem, I’ll take those,” he said with a broad smile.

Of course, we understood that West German DMs were worth much more than GDR (German Democratic Republic) currency. But if that was the price for our freedom, it was a price we were more than willing to pay.

That night as I was speeding my friends back to the relative safety of West Germany, I kept encountering slow-moving, tiny little cars, called Trabants. In fact, I almost ran over one before its image in my rental car’s headlights made clear what it was.

imagesCAUUO69D — The Trabant, Communist era East German car, also known as Trabis.

“That’s odd,” I remarked.

Trabants were a ubiquitous East German car, but I didn’t know that at the time.

If I had, the next sign, a sign for a Baltic Sea town just ahead, wouldn’t have been such a shock.

We had missed a turn and had been driving for over two hours North towards Rostock, still firmly in the depths of Communist East Germany. As I turned around and headed South I was hoping our auto, ostentatious by East German standards, was not advertising the fact that, once again, we did not belong in East Germany.

It was late when we returned to Lüneburg, tired and perhaps a bit wiser. But at least we had all collected a bit of the infamous Berlin Wall to remind us of the fragility of freedom in an uncertain world.

A piece of the Berlin Wall with a rebar impression near the bottom.

Photo of Brandenburg Gate by Florian Wehde on Unsplash.

The Siren’s Call of Rebreather Oxygen Sensors

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.

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.

EX19 — 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 — 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.

http://rebreathers.es/celulas%20o2/celulas%20o2.htm

http://www.rf30.org/

http://www.deeplife.co.uk/or_files/DV_O2_cell_study_E4_160415.pdf

In Search of Glories

Recently my inner child took notice of a circle of light racing across the cloud tops as I cruised at 7000 feet and 180 mph with the prevailing westerlies at my back. I was headed east above the Gulf Coast between New Orleans and the Florida Panhandle, and the late afternoon sun crept ever lower behind my right wing. Like a fighter in loose formation, the ring of colored light was keeping pace with the aircraft, just in front of my left wing.

My adult self realized that the spot contained a shadow of the airplane, but the bright halos around the dark shadow puzzled me. When my inner child asked me what it was, I had no ready answer.

I’d seen those halos before without really understanding them, but now I had a chance to photograph them. I grabbed cameras and recorded the beautiful phenomenon while the autopilot kept the aircraft on course.

One of the advantages of general aviation aircraft is that we often fly at the altitudes of the DC3s, the early airliners. Which meant that at 7000 feet I could open a small window beside me without depressurizing the cabin and give the camera a clear view of what I was experiencing.

An understanding of what I was seeing would have to wait.

[youtube id=”sV90o44sCE8″ w=”700″ h=”600″]

With few exceptions, Glories remain in the realm of pilots and Angels. By association, many pilots feel privileged to see a glory. I know I do.

Without knowing the science behind glories, pilots may even interpret them as signs of the divine. After all, they do look suspiciously like halos seen in medieval religious art. Indeed, “glory” is another name for those iconic halos.

Science is only able to partly demystify the subject of glories. The best technical explanation is that glories are the result of reflections (back-scattering) of sunlight coming from directly behind the observer. The tiny spherical water drops in clouds are the objects that scatter the sun light. Oddly enough, the size of the water droplets determines the size of the glory, which by the way may contain multiple rings as seen on the videos in this posting.

Laven-Fig13 — MiePlot simulation of scattering of sunlight from r = 4.8 µm water drops superimposed on a digital image of a glory taken from a commercial aircraft. From philiplaven.com.

This process of ring formation from water droplets is called Mie Scattering, and is described mathematically by Mie Theory. Phillip Laven’s website, http://www.philiplaven.com/index1.html, provides an ample resource for the curious.

Glories have proven to be such an elusive quarry, that I, like many pilots, have developed a fascination with them. Therefore I could not resist making a brief video, with music, of the glories encountered on that one eastward flight. In it you see a classical glory, followed by a fleeting and hard to photograph glory on the side of a cloud, followed by apparent flight into an ever moving cloudbow.

[youtube id=”CKtkzOpmSUM” w=”700″ h=”600″]

Would You Rather Face a Cunning or Relentless Foe?

Suppose you find yourself on an alien planet, battling with indigenous species. On your side, you have smarts, both natural and technological. The alien defenders have nothing; no technology. Well, they do have slime, but that’s all.

Brains against the brainless: Who do you think will win?

Before the Ticks — Blithely headed into tick-infested woods.

I spent a summer weekend with my family in a cabin in the Virginia mountains a few years ago. It was nature at its finest, until we discovered after a short walk in the woods that ticks seemingly rained down upon us and were invading our bodies as fast as their little legs could move. We were food, and they were hungry. Human-sized meals didn’t come around those woods very often, apparently.

The entire family, adults and children, stripped down to our underwear on the porch of the cabin, trying to rid ourselves of the invaders. Modesty took second place to the fear of miniature arachnids.

Once the imagined itching had abated and the baby was asleep, we soothed our nerves with puzzles and games, or reading from a well-stocked bookshelf. I picked a book with an interesting cover; it was John Scalzi’s Old Man’s War.

I cannot say enough good things about Scalzi’s debut novel, a futuristic science fiction, other worlds story. Suffice it to say, it features combat between Earthling soldiers and all sorts of bizarre and ruthless alien life forms. Although Scalzi didn’t write about invading armies of ticks, per se, I could easily envision such a terrifying encounter.

Cabin 1 crop — This author devouring Scalzi’s “Old Man’s War”.

I also think and write about extraterrestrial aliens. Like most writers, I assume ETs are sentient, and calculating. Depending upon the writer, those ETs may have either high morals, or no morals at all, but they always have a brain.

Lately, I’ve had to rethink potential plot elements dealing with intelligent life forms. The reason is, scientists now claim that a single celled animal, a slime mold, acts with a shocking degree of intelligence. The kicker is, being a single celled organism, slime mold does not have a brain.

800px-Slime_mold_grows_on_anything_001 — Slime mold knows a good thing when it finds it. (Photo credit: SB_Johnny)

Intelligence without a brain?

Compared to slime mold, ticks are geniuses if we count the gray matter cells contained in their single-minded heads. However, according to a Japanese researcher the brainless slime mold can solve problems even scores of engineers could not easily solve.

Sounds like science fiction to me.

So now imagine the following storyline. Your spaceship lands on a verdant planet that has no higher, brain-possessing life forms, at all. However, what it does have in abundance is slime mold. And of course the threat from slime mold is easy to ignore — until it is too late. The mindless protoplasm senses all sources of food, and fans out in all directions, following the scent.

The ship’s science officer tries to warn the mission commander, but the arrogant and miscalculating commander responds with a volley of lead rounds into the nearest slime; which of course is not in the least bit deterred from its food-finding task.

And when the crew sleeps, as of course they must, the brainless mold finds the food sources, one by one, absorbing the human nutrients.

Human-sized meals don’t come around those woods very often, apparently.

Being brainless, slime mold cannot be considered cunning. But, one could argue, it’s not stupid either: it can’t be tricked. It is, if anything, relentless.

From a cinematic perspective this is not an entirely new theme. The 1958 movie The Blob starring Steve McQueen popularized the idea of mindless organisms devouring humans. But at that time there was no real science behind it. Now there is.

Some interesting science facts about slime mold are found in this link and the following Scientific American – NOVA video.

[youtube id=”lls27hu03yw” w=”700″ h=”600″]

In Diving, What is Best is Not Always Good

In technical or recreational rebreather diving, safety is a matter of personal choice. Wrong choices can turn deadly.

Some poor choices are made for expediency, while others are made with the best of intentions but based on faulty or incomplete information. As a diving professional, it is those latter choices that concern me the most.

A poignant and well documented diving fatality involved a record setting Australian diver, David Shaw. David was an Air Bus pilot for Cathay Pacific.

Professional pilots are immersed in a culture of safety, a culture that makes airline travel the surest means of long distance transport. David applied that same sort of attention to his diving, recording on his personal web site his detailed plans for a record setting dive to recover the body of a diver who died in the 890 feet (271 meter) deep Boemansgat Cave of South Africa 10-years prior to David’s ill-fated dive.

Despite his extensive preparations, David Shaw made a fatal mistake. Like those who fail to appreciate the threat of an approaching hurricane, David failed to recognize the risk of really deep diving with a rebreather.

Unlike other types of underwater breathing equipment, a rebreather is entirely breath powered. That means you must force gas entirely through the “breathing loop” with the power of your respiratory muscles. On a dive to 890 feet, you are exposed to 28 times normal pressure, and breathing gas more than five times denser than normal. The effort involved is enough to dismay some U.S. Navy divers at depths far less than David Shaw intended to dive. Yet in David’s own words, he had previously never had a problem with the effort of breathing.

“The Mk15.5 (rebreather) breathes beautifully at any depth. WOB (work of breathing) has never been an issue for me. Remember that when at extreme depth I am breathing a very high helium mixture though, which will reduce the gas density problem to a certain extent.”

He goes on to say, “I always use the best quality, fine-grained absorbent on major dives. The extra expense is worth it.”

“I have had 9:40 (9 hrs, 40 min duration) out of the canister and felt it still had more time available, but one needs to qualify that statement with a few other facts. Most of the time on a big dive I am laying quietly on deco (decompression), producing minimal CO₂ (carbon dioxide).

In those words lie a prescription for disaster.

Scrubber canister — A rebreather scrubber canister containing granular absorbent through which a diver has to breathe.

David wanted to use a single rebreather that would accomplish two tasks — provide a long duration gas supply and CO₂ absorbing capability for a dive lasting over nine hours, and provide a low work of breathing so he could ventilate adequately at the deepest depth. To ensure the “scrubber canister” would last as long as possible, he chose the finest grain size, most expensive sodalime available. His thought was, that was the best available.

Arguably, the two aims are incompatible. He could not have both a long duration sodalime fill and low breathing resistance.

BALLPIT schematic — Cartoon of breathing through a scrubber canister.

As illustrated in a previous blog posting, the smaller the size of granules you’re breathing through, the harder it is to breathe. Think of breathing through a child’s ball pit versus breathing through sand.

Perhaps if David had maintained a resting work rate throughout the deepest portion of his fatal dive, he might have had a chance of survival. After all, he had done it before.

But the unexpected happens. He became fouled and was working far harder to maintain control of the situation than he had anticipated. That meant his need to ventilate, to blow off carbon dioxide from his body, increased precipitously.

A sure sign of high breathing effort is that you cannot ventilate as much as is necessary to keep a safe level of carbon dioxide in your blood stream. CO_2, which is highly toxic, can build rapidly in your blood, soon leading to unconsciousness. From the videotaped record, that is exactly what happened.

Purer A, Deason GA, Hammonds BH, Nuckols ML. The effects of pressure and particle size on CO2 absorption characteristics of High-Performance Sodasorb. Naval Coastal Systems Center Tech. Manual 349-82, 1982. (Click for larger image.)

Had David been fully aware of the insidious nature of carbon dioxide intoxication from under breathing (hypoventilating), he probably would have chosen an alternative method to conduct the dive.

One alternative would be to use a larger granule size absorbent in a rebreather at considerable depth (say, 100 meters and deeper), and reserve the fine-grain absorbent for use in a separate rebreather shallower than 100 meters.

David chose the fine-grain absorbent because of the longer dive duration it made possible. Although fine grains are more difficult to breathe through than large grain absorbent, fine grain absorbent lasts longer than large grain absorbent.

But that long duration is only needed during decompression which is accomplished far shallower than the deep portions of the dive. The time spent deep where work of breathing is a threat is quite short. He did not need the capabilities of a long duration, fine grain absorbent.

From the U.S. Navy experience, there are other problems with this dive which might have hastened the end result. A rapid and deep descent causes the oxygen pressure within the rebreather to climb to potentially dangerous levels; a phenomenon called oxygen overshoot. Thus he might have been affected somewhat by oxygen toxicity. A rapid descent might also have induced the High Pressure Nervous Syndrome which would affect manual dexterity.

While those contributing factors are speculative and not evident on the tape, the certainty of the physics of dense gas flow through granular chemical absorbent beds is an unavoidable fact.

No doubt, many have offered opinions on what caused David’s accident. I certainly do not claim to be intimately involved in all the details, nor familiar with all the theories offered to date. Nevertheless, David’s mistaken belief that using the “best absorbent” was the best thing for his dive, is a mistake that needs to be explained and communicated before this accident is repeated with a different diver in some other deep and dark place.

tim051wc14_61083a — Click to go to the source document.

The Relevance of Genealogy in a Mormonism-Awakening World: or My Ancestors Did What?

Capture — Reconstructed Neanderthal. Click to go to BBC source.

Recent science has revealed that we, Homo sapiens, may be carrying genes from the Neanderthals, like the model on the left reconstructed from a nearly complete skeleton discovered 100 years ago in France. But what about our other genes, those contributed by our family ancestors?

The quest for family roots is old, and has kept genealogists, amateur and professional alike, engaged in a fascinating search of discovery.

That quest has even been politicized, for at least the last five-years, with the public clamoring for information about the roots of presidential contenders. Fortunately for us commoners, information of our forebears is easy to obtain, in comparison, because of its lack of political sensitivity. This search is eased in part by the help of the Mormon Church.

I’m not a Mormon, but if you’ve spent any time at all on the planet lately, you’ve probably heard that a U.S. Presidential contender is, namely, Mitt Romney. My take on Mormons that I’ve known personally is that they are really nice people, with a strong interest in family … and genealogy. I like to think I hold those values in common with them.

They used to say you are what you eat. But now that the war between nature vs. nurture has quieted down, we recognize we are largely what our genes define, with a good bit of good parenting thrown in. But it’s the genes that interest me the most. Supposedly we share 95-98% of our genome, our collection of genes, with Chimpanzees. Well, as I look in a mirror, I realize that remaining 5% is pretty darned important.

And so out of an abundance of curiosity, decades ago I began transcribing my Grandmother’s family history notes into early DOS-based computer databases. Before long I began to see an interesting panoply of historical faces staring back at me.

I soon learned that the Church of Latter Day Saints had extensive libraries chock full of family files, and due to the Mormon fascination with all things family, my database rapidly grew. With the advent of the Internet and family file sharing, the numbers of known ancestors grew exponentially. That’s when things got interesting.

Jura Deer Stalker — Game Stalker … Photograph by Jim Richardson, National Geographic – “Gordon Muir, a renowned game stalker on the island of Jura.”

My Clark(e) ancestors were Scottish, and after coming to the U.S. in the 1700s from Jura, Scotland, they settled in North Carolina. They were thus Southern.

Being Southern led to a conflict between one ancestor, a tall well-educated man who published a Tennessee newspaper, and a carpetbagger during the dark days of Civil War Reconstruction. The abusive carpetbagger threatened my ancestor, publicly, and got shot dead in the process. Unfortunately, the carpetbagger was unarmed at that moment, and carrying a weapon was illegal for the Southerners. That was problematic.

Nevertheless, my ancestor was eventually acquitted. I think the 19th century lesson was, don’t do wrong to a Scotsman, even one in America.

In Scotland, on the Isle of Jura, there seemed to be little to do except make whisky, drink whisky, fight whenever it seemed useful, and contribute the 5% of their unique genes, as often as possible. Not a bad lifestyle, in my opinion.

Some Scotsmen signed an oath of Loyalty to the King of England before leaving Scotland and emigrating to the Unites States. Some of those so-called Loyalists ended-up on the wrong side of the U.S. Revolutionary War.

I admit, some of my Scottish ancestors made bad choices, but they did so with conviction and a sense of honor. A promise made is a promise kept.

The record shows that both Scottish and American women shared a perilous lifestyle, arguably equal in finality with warring Highlanders. The birthing of babies occasionally ended in maternal mortality. Oddly enough, the genes usually won out, because when a mother died, her younger sisters oftentimes were the next to marry the grieving husband. The family genes stayed together, or so says the historical records.

As time went on, the wary North Carolina Scots finally began choosing those with a British ancestry as mates, so the blood lines did not remain isolated for long.

Families have a way of romanticizing their lineage. For instance, I’d always heard that I was related on the maternal side (Harrison) to the unfortunate President William Henry Harrison who died after only 32 days in office. After years of casual researching, there is no relationship, best I can tell.

But I did discover a potential connection to Sir Henry 1st Baronet of Blickling Hall and Chief Justice of Common Pleas Hobart, circa 1500s. (Blickling Hall is reputed to be the most haunted home in the U.K., haunted by the headless ghost of Ann Boleyn.)

I would be impressed with myself, thinking I came from such a distinguished Englishman. But then I realize that his genetic contribution would be like adding a single drop of chocolate syrup to a tanker truck full of milk. We’re a long ways from ending up with a truck full of chocolate milk.

So what is the relevance of all this esoteric knowledge to our daily lives? Well, to the Mormons it’s very relevant, for religious reasons. It’s their way of extending salvation to lost souls; an admirable motivation.

For the rest of us, the relevance is less compelling, unless you enjoy discovering stories like those I’ve shared. It’s like seeing a reality show with an entirely new episode revealed each time you turn on the computer. And in the rolling credits of this show are people who happen to be in some way related to you, contributing the parts of you that make you unique.

Personally, I think history is much more interesting when it is your own.

Is Your Local Ball Pit Safe for Children?

http://nl.wikipedia.org/wiki/Bestand:Ballpit.jpg

I sat on the edge of a ball pit at Chuck E. Cheeses, calipers in hand, measuring the diameters of a random sampling of plastic balls within the pit.

I suppose I stood out, an officious-looking adult wielding a precision instrument in a place designed for fun. So much so that a father attending his child asked me what I was doing.

I was measuring the ball sizes. I explained that if the balls were too small, and a child became covered with them, then the void space around the balls, the contorted empty volumes that represented places where air can be exchanged, would be too small, making breathing difficult. That made sense to the father, and he seemed pleased that I was looking after his child’s safety.

A child is almost completely covered by balls. A single hand is sticking out, and part of a face can be seen.

Contrary to the way it seemed, I was not a corporate inspector for Chuck E. Cheeses. I was also not a government inspector. But I was curious, gaining information for ideas I was developing about the breathing resistance imposed by particles of various sizes. I was acting, as it were, as a freelance scientist investigating flow through porous beds.

Consider the circumstance where a person is forced to breathe through a mass of balls, as in the illustration below. You can see, better than in the case of the ball pit, that if the balls become too small, or smaller balls fill in the void spaces between larger balls, then the person would be at risk for suffocation.

Advertisements for balls sold for ball pits point out the safety advantage of larger balls for children under age 3. The smaller children are obviously more susceptible to tunneling deeper into a pit of balls, some of which may be piled to two feet or deeper depths.

Balls of 3.1 in. diameter are touted as being ideal for three-year-olds, whereas other popular sizes [2.5 in. (65 mm), 2.75 in. (70 mm)] are not. The 3.1 in. ball is almost twice as large, in terms of actual volume, as the 2.5 in. balls.

A problem awaits a child if the ball pit has poorly sorted ball sizes, especially a mixture of larger and small balls. As shown in the figure to the right, well-sorted balls provide a porosity (airspace for breathing) of over 32%, whereas a mixture with balls fitting into the void spaces between larger balls can reduce void space down to about 12%. That would not be a good plan for a ball pit.

It also is not a good plan for the Namib mole.

The Namib Golden Mole is found in one region of Namibia because of the peculiar characteristics of the sand in that area. The sand grains are surprisingly homogeneous in size, and as the illustration to the right shows, similarly sized particles have a relatively large porosity. For the mole that means that when they burrow deep into the sand to escape blistering noonday heat, they will not suffocate. They can breathe through the sand.

If the sand were of mixed grain sizes, which is more typical of sand dunes, then porosity would be low and the mole would not be able to burrow deep enough to avoid the African heat without suffocating.

So, quite unexpectedly there is a connection between the uniform size of plastic balls in a ball pit and the survival of a mole in a faraway African desert.

You never know where scientific curiosity will lead you.

As will be shown in an upcoming blog post, the topic of breathing through porosities in packed beds is relevant to diving with rebreathers or breathing through chemical absorbent cartridges in gas masks.

Making Fuel

avo-small — Buffalo Airways C-46 Commando.

While watching an “Ice Pilots” episode on the Weather Channel I heard a pilot of a Curtiss C-46 Commando talking to his inexperienced copilot during a flight. At one point he said they were “making fuel.”

I have enough common sense and experience as a pilot to know that could not be literally true. But I had no idea what the Ice Pilot’s comment really meant until recently returning home during a non-stop flight from Dallas, Texas to the Florida Panhandle.

I had purposefully climbed to 11,000 feet to catch good tailwinds heading east. The winds were even stronger at higher altitudes, but if I’d climbed to the next allowed altitude, 13,000 feet, my passenger and I would have needed to wear an oxygen mask. And I’d left the oxygen system at home.

During flight planning before departure, it looked as if going high would give us enough of a tailwind that we would be able to make the trip without a time consuming fuel stop.

Modern aircraft often have fuel computers communicating with the aircraft GPS navigation system. Fuel computers track every ounce of fuel burned during taxi and flight. The pilot programs the total fuel available and then the fuel computer checks with the GPS to see how many miles remain to the destination, and the ground speed. Every few seconds the pilot sees an update of the fuel burned, gallons remaining, predicted flight time available, the fuel required to reach the destination, and the bottom line, the predicted fuel reserve at the destination.

Typically, I want to land with no less than 10 usable gallons remaining, which is enough to remain aloft for an additional hour at the normal fuel consumption rate. If the weather is bad at the destination, then the required fuel reserve is considerably larger.

On the first phase of my flight to Dallas, once I had reached cruising altitude the fuel computer calculated that if the current ground speed and fuel burn were to continue to the end of the trip, I would have five gallons of fuel left at the destination. That is not enough for safe flight, so a refueling stop was looking inevitable. As the flight continued, the estimation of reserve fuel barely budged from its first estimate. In other words, nothing was changing, and the decision to refuel was firmly made.

East Texas from 11,000 ft. Click to enlarge.

On the return flight, however, flying relatively high where the prevailing westerlies were strong, the computed reserves (RES) were changing. They were growing. As the flight progressed I watched the estimated fuel reserve rise slowly from 8 gallons to 9, then 10, and finally 11.4 gallons. By the time we landed we had 12 gallons of fuel remaining in the two fuel tanks.

It truly looked like we were making fuel.

We weren’t, of course. The reality of it was that the tailwind was increasing in our favor for the east-bound trip. But the fuel computer gave every impression that for every gallon of fuel we burned, we were getting a little bit back.

I finally understand what the Ice Pilot meant; I think. If I ever meet him, I’ll ask.