jclarke45 | John Clarke Online

Redundancy – a Life Saver in Diving and Aviation

Photo taken from the author’s aircraft one stormy Florida Panhandle morning. (click to enlarge)

I was recently flying a private aircraft down the Florida Peninsula to Ft. Lauderdale to give a presentation on diving safety. As I continually checked the cockpit instruments, radios and navigation devices, it occurred to me that the redundancy that I insist upon in my aircraft could benefit divers as well.

In technical and saturation diving, making a free ascent to the surface is just as dangerous as making a free descent to the ground in an airplane, at night, in the clouds. In both aviation and diving, adequate redundancy in equipment and procedures just might make life-threatening emergencies a thing of the past.

Aviation

As I took inventory of the redundancy in my simple single engine, retractable gear Piper, I found the following power plant redundancies: dual ignitions systems, including dual magnetos each feeding their own set of spark plug wires and redundant spark plugs (two per cylinder). There are two sources of air for the fuel-injected 200 hp engine.

There are two ways to lower the landing gear, and both alarms and automatic systems for minimizing the odds of pilot error — landing with wheels up instead of down. (I’ve already posted about how concerning that prospect can be.)

I also counted three independent sources of weather information, including lightning detection, and two powerful communication radios and one handheld backup radio. For navigation there is a compass and four electronic navigation devices: one instrument approach (in the clouds) approved panel mount GPS with separate panel-mounted indicator, an independent panel mounted approach certified navigation radio, plus two portable GPS with moving map displays and superimposed weather. Even the portable radio has the ability to perform simple navigation.

photo (17) - no Exif — There’s two of just about everything in this Arrow panel.

The primary aircraft control gyro, the artificial horizon or attitude indicator, also has a fully independent backup. One gyro operates off the engine-powered vacuum pump, and the second gyro horizon is electrically driven. Although by no means ideal, the portable GPS devices also provide attitude indicators based upon GPS signals. In a pinch in the clouds, it’s far better than nothing. Of course, even if all else fails, the plane can still be flown by primary instruments like rate of climb, altimeter, and compass.

There is only one sensitive altimeter, but two GPS devices also provide approximate altitude based on GPS satellite information.

Diving

But what about divers? How are we set for redundancy?

Starting with scuba (self-contained underwater breathing apparatus), gas supplies are like the fuel tanks in an aircraft. I typically dive with one gas bottle, but diving with two or more bottles is common, especially in technical diving. In a similar fashion, most small general aviation aircraft have at least two independent fuel tanks, one in each wing.

The scuba’s engine is the first stage regulator, the machine that converts high pressure air into lower pressure air. Most scuba operations depend on one of those “engines”, but in extreme diving, such as low temperature diving, redundant engines can be a life saver. While most divers carry dual second stage regulators attached to a single first stage, for better redundancy polar divers carry two independent first stages and second stages. Two first stage regulators can be placed on a single tank.

tv9200rhlg[1] — An H-valve for a single scuba bottle. Two independent regulators can be attached.

Two Regs — A Y-valve for Antarctic diving with two independent scuba regulators attached.

Even then, I’ve witnessed dual regulator failures under thick Antarctic ice. The only thing saving that very experienced diver was a nearby buddy diver with his own redundant system.

There is a lot to be gained by protecting the face in cold water by using a full face mask. But should the primary first or second stage regulator freeze or free flow, the diver would normally have to remove the full face mask to place the second regulator in his mouth.

Two regulators, one full face mask. Photo courtesy of Michael Lang and Scuba Pro.

Reportedly, sudden exposure of the face to cold water can cause abnormal heart rhythms, an exceedingly rare but potentially dangerous event in diving. If the backup or bail out regulator could be incorporated into the full face mask, that problem would be eliminated. The photo on the right shows one such implementation of that idea.

Inner Space 2014_Divetech _Nikki Smith_Rosemary E Lunn__Roz Lunn_The Underwater Marketing Company_Nancy Easterbrook_rebreather diving_2014-05-27 22.30.47 — Nikki Smith, rebreather diver with open circuit bailout in her right hand. Photo courtesy of Rosemary E Lunn (Roz), The Underwater Marketing Company.

Rebreathers are a different matter. Most rebreather divers carry a bailout system in case their primary rebreather fails or floods. For most technical divers, that redundancy is an open circuit regulator and bailout bottle. However, there are options for the bail-out to be an independent, and perhaps small rebreather. (One option for a bail-out semiclosed rebreather is found here.) Such a bail-out plan should provide greater duration than open-circuit bailout, especially if the divers are deep when they go “off the loop”.

SPECWAR1 — U.S. Navy photo by Bernie Campoli.

For some military rebreather divers, there is at least one complete closed-circuit rebreather available where a diver can reach it in case of a rebreather flood-out.

SLS-Diver-Side-View — A commercial saturation diver with semi-closed rebreather backpack as emergency bail-out gas.

For deep sea helmet diving, the bail-out rebreather is on their back and a simple valve twist will remove the diver from umbilical-supplied helmet gas to fresh rebreather gas.

The most common worry for electronically controlled rebreather divers is failure of the rig’s oxygen sensors. For that reason it is common for rebreathers to carry three oxygen sensors. Unfortunately, as the Navy and others have noted, triple redundancy really isn’t. Electronic rebreathers are largely computer controlled, and computer algorithms can allow the oxygen controller to become confused, resulting in oxygen control using bad sensors, and ignoring a correctly functioning oxygen sensor.

The U.S. Navy has performed more than one diving accident investigation where that occurred. Safety in this case can be improved by adding an independent, redundant sensor, by improving sensor voting algorithms, by better maintenance, or by methods for testing all oxygen sensors throughout a dive.

In summary, safe divers and safe pilots are always asking themselves, “What would I do if something bad happens right now?” Unfortunately, private pilots and divers quickly discover that redundancy is not cheap. However, long ago I decided that if something unexpected happened during a flight or a dive, I wouldn’t want my last thoughts to be, “If only I’d spent a little more money on redundant systems, I wouldn’t be running out of time.”

Time, like fuel and breathing air, is a commodity you can only buy before you run out of it.

Disclaimer: This blog post is not an endorsement of any diving product. Diving products shown or mentioned merely serve as examples of redundancy, and are mentioned only to further diver safety. A search of the internet by interested readers will reveal a panoply of alternative and equally capable products to enhance diver safety.

When Cars Can Tweet

I was quite surprised when I learned that the U.S. government is mandating, and U.S. engineers are devising, ways for cars to share messages about their status, speed, and location. That is, they will be talking to each other.

What will that talking sound like? Well, I don’t think its going to be like Mater in Disney’s Car series.

I suspect it will probably resemble something like minimalistic messaging —to save bandwidth.

Here’s an example of what it might sound like:

RedHondaCivic564: “OMG, my peeps is a lunatic.”

BlackAccuraJ76: “How so?”

RedHondaCivic564: “He’s straddling the center line!”

BlackAccuraJ76: “LMAO. What a twit.”

RedCherokeeH65: “Watch out, I’m swerving, coming up fast on your six.”

OrangeSonata97B: “What’s the prob?”

RedCherokeeH65: “My peeps is a stoner. Smoking weed in the car. ”

BlackAccuraJ76: “Is that bad?”

RedCherokeeH65: “It’s filling my passenger compartment. Cough, cough.”

BlackAccuraJ76: “I should be so lucky.”

RedCherokeeH65: “Uh _ why are pink bunnies dancing on my hood?”

OrangeSonata97B: “Seriously? Turn your AC to outside air.”

RedCherokeeH65: “Ah, much better. No more bunnies.”

Maserati I’m a Doc: “Out of my way! Move over!”

RedHondaCivic564: ‘What’s ur rush pretty grl?”

Maserati I’m a Doc: “I’m a go-fast car.”

Ford: “Sucks for you since ur stuck in a 45 zone.”

Maserati I’m a Doc: “Tell me ’bout it. So frustrated.”

Ferrari SiliconeDoc: “Me too. I never get my pipes cleaned.”

PinkMercedes: “SiliconeDoc, like the sound of that. Talk to me.”

BlackAccuraJ76: “Watch out for that poo…”

RedCherokeeH65: “Oh crap.”

BlackAccuraJ76: “…dle!”

FordKJ7: “Cute the crap folks. We’re s’posed to be talking safety.”

RedHondaCivic564: “Yeah right. Boring!”

UnknownCaddy: “Get over, make way!”

RedHondaCivic564: “Another fast mover? What’s your hurry?”

UnknownCaddy: “Getaway car.”

RedHondaCivic564: “What are you getting away from?”

UnknownCaddy: “Cops.”

Copper1: “Thanks for that.”

UnknownCaddy: “What you mean?”

Copper1: “I’ve gotta a BOLO out for you.”

UnknownCaddy: “Did you just hit my kill switch?”

Copper1: “Do the crime, do the time.”

Does Your Rebreather Scrubber Operate in Its Goldilocks Zone?

gliese581d — 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.

Capturecan1 — 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.

Capturecan2 — 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.

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.

My Medicines Saved my iPhone

I’ve heard about all sorts of disasters with smartphones, and other small, portable electronic devices. Being small and portable makes them easy to drop — something I’ve personally witnessed. Phones are tough by design, but they really don’t like water. Drop one in a toilet while you’re relaxing, and it’s gone — for all practical purposes.

So I had my phone outside with me one evening while I was safety diver for my granddaughter who was practicing scuba skills in our pool. She was enthusiastic and stayed in the pool until it became completely dark outside.

Well, out of sight, out of mind. I helped her out of her dive gear, and then went inside. The phone stayed outside in the dark, quite forlorn and forgotten.

Next morning I noticed it had rained in the early morning hours. Great, I thought, the lawn needs water. But when I went outside I discovered my phone sitting face up on a glass table with beads of water everywhere, including on the phone. A few expletives followed, as you might imagine.

My phone had been somewhat protected by an almost all enclosing Otter box, so I was hopeful not all was lost. Indeed, when I brought the phone in, removed the Otter box sheaving and dried off the phone with paper towels, the phone came back on. Immediate disaster avoided. Thank-you Mr. Otter.

But it took a little while before the potential damage became apparent. When my phone would ring, I’d hear nothing on the ear speaker. I had to switch to speaker phone mode to hear anything. Well, that was annoying.

And then I tried to take a phone photo of the scuba gear, and I could barely see through the camera view finder for the obscuring droplets of water. Rats! Clearly, water had gotten inside the phone. It was merely a matter of time before more damage was done.

With nothing to lose, I plundered through my medicine cabinet and found a potential solution, pictured below.

In fact, I found four of them. I placed those small cylinders of silica gel in a quart-size zip-lock style bag, and placed the dampish phone inside and sealed the bag after squeezing out excess air. If the silica gel canisters didn’t hurt the medicine, it probably wouldn’t hurt my ailing phone.

And there the phone sat, with the small vials of desiccant.

I don’t pray for the healing of phones, but I did have some thoughts somewhat resembling prayer.

I let the phone-in-a bag sit overnight, and in the morning I found I could hear the voices on the other end of the phone connection, and my camera lens no longer had droplets of water on it. As you can see from these photos, the camera worked just fine, and all functions have worked fine ever sense.

Even Siri didn’t seem to mind getting rained on.

I am Neanderthal, Pt. 3

image_1734-Neanderthal-DNA — Neanderthal. Image credit: Trustees of the Natural History Museum, London.

I feel like a seeded watermelon.

Ever since I was created by the curiosity of government and university scientists, I have lived through no efforts of my own. I have the largesse of the U.S. government to thank for that. You see, they paid for the research that created me.

And now, I contribute nothing to society. I pay no taxes, work no jobs. The only decisions I’m allowed to make are restricted to which television program to watch, or which book I want to read. (In case you wondered, I’m not a slow reader. I read quite well, thank-you.)

I live basically in a zoo, except I am the only specimen there, and the zoo keepers all wear lab coats. I suppose the lab coats are designed to protect them were I to spit on them or throw excrement.

I admit, as a child I used to act out with what you consider primitive behavior, throwing feces to vent my anger. I do have tough skin, but no child wants to be continuously poked and needled and questioned. Would you?

But I’ve outgrown that. I’ve learned that when it suits me I can produce a terrifying stare or a teeth-bared snarl that scares the crap out of the more timid researchers. Ah yes, I do enjoy having fun at their expense. It’s about the only thing they can’t control in my otherwise manufactured and manipulated world.

And of course they don’t dare punish or threaten me, because I am, after all, the rarest person in the universe, the only living Neanderthal.

But about that watermelon?

Having nothing to do of any real value gives me time to think … lots of time. Now, since a part of me is a part of you (genetically that is), I’ve been inclined to wonder why my kind is gone, and you Homo sapiens have become the overlords of the planet, at least for the time being.

And I’ve decided that I am truly a seeded watermelon, and you’re seedless.

The seedless watermelon is very much like the older, and almost extinct seeded variety, but with one subtle difference; it’s infertile. (If this analogy becomes too Freudian for you, just keep your mind on watermelons.) Watermelon is, I sincerely believe, one of God’s gifts to man.

But of course you Homo sapiens weren’t content with that. No, you decided to take advantage of a genetic flaw, a freak watermelon with few if any seeds, that is quite incapable of sustaining itself in the gene pool.

Since spitting out melon seeds is apparently such a difficult proposition for your kind, the seedless variety is overwhelmingly popular. It has crowded out the natural watermelon from grocery stores, so I hear.

Photo Credit: Steve Evans (Watermelons) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

I’ve been reading about how, based partially on my IQ test results and other research, scientists have decided we weren’t mentally inferior to you. And for sure, as my own testing by the Army has confirmed, we were far stronger.

So what’s not to love?

OK, we are a little shorter, squattier than Homo saps, and from what I hear tall men have a selective breeding advantage over shorter men. So could it be simply a matter of Neanderthal women preferring to breed with you guys, the new kids on the block, and not with us more vertically-challenged guys? Could that be why my kin disappeared, and why many of you have Neanderthal genes?

I mean, really, could it be that simple; a matter of sexual attraction? Did short-sighted Neanderthal women breed our unique species out of existence?

Well, who would have thought an infertile and obviously biologically deficient watermelon would have replaced the real thing in popularity?

But it has.

Where Have All the Letters Gone?

SONY DSC — By Petar Milošević (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

When is the last time you wrote a letter to a family member or loved one?

I’m not talking about email or text messages; digital communications do not count. I mean a letter on a piece of paper, placed in an envelope with a stamp, and mailed at a mailbox or post office; or in a very private way, lovingly slipped underneath someone’s door.

In the hurry-up, speak sparingly Twitter generation, there seems to be little value in penning an honest-to-goodness letter. Compared to instant communication, letter writing with an ink-filled pen seems agonizingly slow, sloppy and so twentieth century.

I recently opened a grey metal box that had lain dormant, ignored, for up to 50 years. It was a time capsule, holding remnants of this young man’s life in 1964 and before. In it were letters, letters my Dad had written to me during my college years.

My parents have been gone for many decades now and reading those letters after such a long time was a joy. Unlike emails and tweets, those letters told a story, a story of how my parents were reacting to and appreciating my newfound freedom and expressions of individuality.

My father, a physician who practiced medicine for 50 years, wrote words that are even deeper in meaning now than they seemed at the time. “We are glad that you seek the places that are apart, such as the mountains and the sea,” he wrote. “It is so easy to rush past the beauty and truth of life, especially in this age. An older and wiser one once said, ‘Let us not hurry, not worry, and let us take a moment now and then to smell the flowers along the way.’ “

And then there were the words I puzzled over briefly before realizing what it meant. “Their being and meaning will never know the obsolescence of most of that which is taught.”

Frankly, that was a lesson that takes a lifetime to understand, for in time we come to know that many things we are taught while young will eventually be found wrong, or at least inaccurate. In other words, so-called truths change.

In 2064, fifty years from now, how will you or your descendants be reminded of things you said or things your parents and other loved ones thought way back in 2014? How will memories of 2014 be renewed?

Even now, the concept of writing love letters seems sweet but archaic to those in their twenties. So I wonder, will there be such a thing as love letters in the future?

Facebook posts certainly won’t be preserved for fifty years. In fact, both Facebook and Twitter will be long forgotten, replaced by more culturally relevant trends. And let’s face it, have you ever said anything on Facebook that deserves to be preserved for fifty years?

I suppose that as my father saw his time on earth becoming increasingly limited, he realized that time, the time to enjoy life, was a precious commodity, yet one not well appreciated until the sand in the clock is half run out. That is an important lesson that I, with my own sand ebbing away, have at last come to appreciate. But if I did not have my Father’s letter to read now, fifty years later, it would be a lesson long forgotten.

In a tweeting, Facebook society, how will we hold pages and memories in our hands when our parents and other loved ones are gone?

Sad to say, I don’t think we will.

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.

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.

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.)

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

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.

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.

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

Do All Boys Cause Their Mother Grief, or Is It Just Me?

Mother’s Day 2014 has come and gone, but not without my thinking of the grief I caused my ever patient, ever tolerant, and certainly loving Mother.

I think the only time when I didn’t surprise her was when I was born. She always called me “Johnny on the Spot” since I was apparently born on my (or is it her? Make that our…) due date.

I’m sure there was some surprise when I turned out to be a curly headed blond with green eyes … like no one else in the immediate family. Hmmm… But at least there was no grief involved, other than the usual wailing and gnashing of teeth accompanying child birth.

The grief started apparently about the time I became mobile. I was probably the youngest toddler in Fort Smith, Arkansas to try to climb a fence, and break a collar bone in the attempt. What was I thinking? I could barely walk, much less climb?

Fortunately I don’t remember it.

But I do remember my first toddler “run away from home” attempt. I toddled maybe half a block down a hill before my brother caught up with me and led me back home, luring me with the words I still remember: “Mom’s cooking bacon!” Well then, that’s different!

If only all toddler insurrections could be ended so crisply.

As for collar bones, my first break was not my last. A few years later I broke the other collar bone, an event I do remember well. My Dad, an orthopedic surgeon, was able to put my shoulder in a sling quicker than a quick draw artist could draw a pistol. He was good, and I kept him in practice.

I also acquired an assortment of scars on my left knee which the Army was later pleased to find out about. You know, they wanted to be able to identify my body just in case all that was left of me was my left knee.

I guess having been a rambunctious boy was good for something.

Riding a borrowed bicycle into the back of a parked car was not my brightest move as a child. I knocked myself out cold. When I woke up, I remember telling my Mom “My head hurts.” As much as she wanted to, she could do nothing to ease the pain of my concussion.

Shortly after that, we moved to Texas, where I broke my collar bone again.

After a move to Kansas, Mom and I rode a train to California to visit my much older sister and my Mom’s sisters. On the way, I got motion sick and threw up all over some nice lady’s dress. I was too sick to be embarrassed, but my poor suffering Mom had to endure yet another indignity forced upon her by her woe-begotten son.

I’m sure she was wondering why God had blessed her with a fourth child so late in her child bearing years (yes, I was involved in an accident even at my conception). About the time she took a nap and I disappeared into the California desert wilderness, she must have been thinking how much nicer three kids would have been rather than four. She thought I was lost in the desert, but I knew where I was. I saw a snow-covered mountain in the distance and thought it would be cool to walk to it in the 120° heat, just to play in the snow.

A kid raised in flatlands has no sense of distance, because I now know that from where I left the travel trailer at Palm Springs the nearest tall mountain is a distance of at least 50 miles. After covering maybe a half a mile over rocky desert hills, my half baked brain realized that perhaps snow was out of reach.

That Mom and half the residents of the trailer park were searching for me did not occur to my 5th grade brain until I crested the closest ridge and heard men on the desert floor calling for me. She of course was frantic, and then relieved, and I was glad to get back out of the parching sun.

She was no doubt wondering if her last of four kids would be the death of her.

Later that year I got knocked out again, at school (5th grade boys can be rough) but I could tell Mom and Dad were becoming desensitized to my traumatic injuries. I always seemed to bounce back just fine.

Now that I think about it, my early adult years were only a little less disturbing for Mom. There was the time in graduate school when I was simultaneously knocked out, yet again, and had yet another bone broken; my jaw this time — I never saw the hit coming. Of course Mom, who was far away at the time, could do nothing but worry about her son’s proclivity for repeated injuries.

Perhaps I was suffering a little from repeated Traumatic Brain Injury when I decided to ride a 50 cc Honda home to Kansas from Atlanta, without telling the folks how I was getting home. Poor Mom got a migraine out of that escapade, but I almost made the distance before burning up the little engine.

I think I now understand the meaning of “long suffering.”

Shortly after she passed away from a surgical misadventure, I found myself on a beach, with my first airplane, trying to figure out how I was going to get out of this pickle. So I decided to talk to her. I found it comforting.

But just now I’m imagining what she was thinking when her spiritual duties were interrupted by a call from her troublesome boy.

“Oh, it’s you again. What have you done to yourself now?”

After I confessed my predicament, she probably said (but I can’t swear to it), “I feel another migraine coming on.”

Happy belated Mother’s Day Mom! I didn’t mean to be such a pain in the neck; it just comes naturally to some people. But I do love you!

What Is That Music?

The mark of great music is that you will always remember where you were and what you were doing when you first heard it.

In early 1977 I was a young First Lieutenant in the Army, training at Aberdeen Proving Ground, Maryland. I had flown up there to attend 3-months of Active Duty for Training. It was winter, but on one weekend when the weather promised to be beautiful, several of us piled into a car and headed South to Washington, DC. None of us had been to DC before, so the trip was one of discovery and high expectations.

For a space and aviation enthusiast like myself, the long-anticipated highlight of the trip was the chance to see the newly opened Smithsonian Air and Space Museum, and to see my first Imax movie, which happened to be “To Fly”.

In the dim light of the large sloping theater, we waited for the movie to begin. Meanwhile, music was softly playing.

You know how when you’re at a restaurant or bar and someone is playing, you’re not necessarily aware of the music per se. It’s just part of the ambiance, the background. But as that music began, it started with deep strings, rhythmically, methodically stroking through the music.

Deep bass notes have always thrilled me. I am a player of clarinets, which have no bass properties to speak of, so perhaps it is the novelty of bass that so captures my imagination. And so it had slowly begun to work on me, that anonymous music.

It was clearly classical, most likely some well-orchestrated version of what must have originally been chamber music. As I listened ever more attentively, the music built on itself and added complexity which maintained and then grew my interest. I had never heard it before, and neither had my friends, but I began questioning myself, “What is this music?”

After over four minutes, when you would think the pace and melody would be becoming somewhat worn, the composer threw in some accidentals, which frankly shocked me, as they must have the music’s first listeners. There was a string of four eighth notes, and one of them sounded flat, while its pairing just two notes away was not. What is this, I thought? And then in the next measure, it was repeated, so it certainly wasn’t a mistake. It was an intentional musical device and one that I loved for its novelty.

It was as if the composer had been holding back for that subtle surprise until near the end of the piece. Just as you thought you knew what to expect, something new appeared in the melody.

Strangely, I left that theater thinking as much about that mysterious theatrical prelude as about the movie. And for an aviation enthusiast, that’s saying a lot.

Before long, I began to hear that piece elsewhere, and with increasing frequency. In fact, the music enjoyed a burst of popularity starting in the early 1970s, the same period when I first heard it.

If you haven’t guessed by now, I’m talking about Johann Pachelbel’s Canon in D. It is now so well known that it has its own web site. The following video featuring Canon in D was compiled by “diemauerdk.”

According to the Internet, Canon in D first became available to the masses through a 1970 recording, reportedly by the French musician Jean-Francois Paillard. Oddly, even though it was written in about 1680, it was not published until 1919. I have no doubt that its rise in popularity was due in no small part to the large audiences exposed in the iMax theater at the Smithsonian Air and Space Museum. The fact that it was the main theme of the 1980 popular movie, Ordinary People, only helped to propel it to mainstream consciousness.

On viewing the piano sheet music it’s easy to spot where the usual C# F# structure of the key of D is flatted to produce an appealing effect. The four notes of note, if you will, are D C natural B C#. To an ear accustomed to hearing C# throughout most of the piece, a C natural sounds flat; but in a delightfully unexpected way.

I consider myself lucky to be one of the first Americans to hear what was to me new music and to appreciate that it was a very special work indeed. However, I must wonder; three hundred years from now, do you think any works from present-day artists will be “discovered”, and enjoy almost universal popularity?

Nightmarish Thoughts of Being Eaten

There is a downside to situational awareness.

I discovered this fact while 868 miles north of the Arctic circle, 600 miles south of the North Pole. It took place in Ny-Ålesund, Svalbard, a part of the well-known island Spitsbergen.

I was helping the Smithsonian Institution train divers in polar diving. My job was to teach them about scuba regulator performance in frigid water.

A fact of life in Ny-Ålesund, the most northern continuously occupied settlement, a research village, is that Polar Bears are always a threat. In fact, one came through town during our visit to Svalbard. The Greenland sled dogs, tied down outside, were understandably, and quite noisily, upset. The bear walked right past them.

After the excitement of that nighttime polar bear prowl had begun to wane, the incident remained as a not so subtle reminder during seemingly routine activities. For you see, polar bears are emotionless killers; to them, we are prey. Tracking and eating a human gives it no more pause than us picking blackberries alongside the road. For adult polar bears, humans are simply a conveniently-sized food item, not nearly so fast and wily as their typically more available meals, seals.

Unlike the ploy of divers bumping potentially predatory sharks on the nose to dissuade them from biting, bumps on the nose don’t work with polar bears. Without a gun by your side, a walk in Svalbard is a walk on the wild side, and not in a good way.

I was observing and photographing boat-based diving operations from the end of a long pier jutting 375 feet (115 m) into the Kongsfjorden. Normally in March the fjord is ice covered, but the year I was there (2007) there was no ice to be seen except at the nearby glacier.

I had been standing at the pier’s end for a while taking photographs, and soaking up the polar ambiance, when I looked back and realized that from a safety standpoint, I was vulnerable. That is when situational awareness began to kick in.

We were in a deserted, industrial portion of the town. The old coal mining operations were shut down long ago. Other than the divers on and in the water, I was the only one around. And I was stuck out on the end of a very long pier, with no means of escape.

If an intruding and hungry bear made its appearance at the land side of the pier, I would be trapped. Although I was dressed for cold, I was not dressed for cold water. That water was, after all, ice water. Polar bears, on the other hand, are excellent swimmers in polar water. So after I’d jumped into the water, which I would have if faced with no alternative, it would have taken the bear only a few furry strokes before he would have me. While he or she would find my body parts chilled on the outside, my internals would still be pleasantly warm as they slid down its gullet.

Being a sensible person, I called the boat drivers over and put them on alert; should a polar bear appear at the far, land-side end of the pier, they should pick me up post haste. Otherwise, there would be no way I could safely escape from my vulnerable position. No photograph is worth dying for.

Being nice fellows, they agreed they would keep an ear out for my shouts. They then returned to their duty of waiting for and recovering the divers.

As the boat eventually sped off with its load of thoroughly chilled divers, I realized that I had been deluding myself all along. At their distance and with the noisy interference of the boat motor, my shouts would have been inaudible. And from their low position on the water, they would have been unable to see what I was so agitated about; until it was too late.

My return back to the safety of the diving center was a cautious one; with the full realization that I was exposed and vulnerable for the entire route. Fortunately, safety was only a third of a mile away, but that was a long 500 meters, which gave my alert mind plenty of time to focus on walking quietly, and avoiding being eaten.

Nothing focuses the mind like knowing that close by, hidden by piles of snow, could be lurking a camouflaged predator looking for lunch.

This Youtube video shows a Polar Bear searching for food in Ny-Ålesund during the brief Arctic summer.