Blog | John Clarke Online

How Does Your Rebreather Scrubber Handle the Deep?

If you’ve planned a deep dive, to say 100 meters or deeper, you may have wondered just how your rebreather scrubber will handle that depth. Since pressure is equalized across a carbon dioxide (CO₂) absorbent canister within a rebreather, it won’t implode. But what about the chemical absorption reactions occurring within the scrubber?

The rebreather scrubber is a vital part of your underwater life support system, so that question is a pretty important one. And the answer is very hard to find.

I recently traveled to Ireland to act as an external examiner for a Ph.D. student’s Doctoral Dissertation defense in the Department of Mechanical, Biomedical, and Manufacturing Engineering of the Cork Institute of Technology. The very talented graduate student was Shona Cunningham, and her dissertation was titled, “Carbon Dioxide Absorption and Channeling in Closed Circuit Rebreather Scrubbers”. She’s an athlete, musician, and perhaps most importantly for you readers, an avid diver.

Her work is the first computational fluid dynamic representation of scrubber canister thermokinetics. A portion of her dissertation work has already been published. Apparently, it was partially inspired by some of my computer simulation descriptions posted on this blog, which can be found here, here, and here.

Dr. Cunningham’s analytical approach (using Ansys CFX) showed that ambient pressure (depth) could reduce the effectiveness of scrubber canisters. In support of that finding were the words from the Dive Gear Express website regarding the Diverite O2ptima using the ExtendAir scrubber cartridge.

“As pressure increases the total number of molecules, the relative concentration of CO₂ molecules in the loop is reduced, slowing the chemical absorption process. Thus as depth increases, scrubber efficiency will decrease.”

The U.S. Navy has no experience with the Diverite O2ptima, but they have information on other rebreathers using granular absorbent. That experience shows that there is no reliable depth effect across all rebreathers and all absorbents.

U.S. Navy MK 16. US Navy photo by Bernie Campoli.

For example, in one rebreather there was indeed a 17% decrease in endurance using large grain absorbent (Sofnolime 408) at 50°F in descending from 190 fsw to 300 fsw (58 to 92 msw) breathing air. However, there was no decrease in duration when using fine grain absorbent (Sofnolime 812) under the same conditions. (On an actual dive, air would never be used at 300 fsw, but air was used in this study for scientific reasons.)

In another rebreather using Sofnolime 812, for a change in depth from 99 fsw to 300 fsw (30.3 to 92 msw) there was a 29% increase in duration at 75°F, a 10% increase at 55°F, and a 15% decrease at 40°F. Although air diluent was used at 99 fsw, 88/12 heliox diluent was used at 300 fsw.

From another manufacturer, I obtained information on two of their rebreathers. At 4°C, 1.6 L/min CO₂ injection rate (corresponding to a fairly heavy work rate), 40 L/min ventilation rate using air diluent, there was a 27% decrease in one rebreather in going from 15 to 40 msw (50 fsw to 132 fsw), and a 11% decrease in another of their rebreathers in dropping from 40 msw to 100 msw.

In another rebreather tested under the same conditions except for depth, the canister duration dropped 39% between 15 and 40 msw.

So, there is some support for a drop in duration with depth, but in other cases, there is either no effect or an increase in duration with deeper depths. Clearly, if the high number of inert gas molecules coming with a pressure increase makes it more difficult for CO₂ to reach absorption sites, then that would be a simple and unavoidable fact of physics. But that cannot be the whole story. What is likely to be going on, a hypothesis, is being developed for a later posting.

Should the effect of depth on your particular rebreather matter to you? Logically it shouldn’t. Even on a deep dive, the majority of the dive time is spent shallow, decompressing.

However, consider the case where you conduct a deep dive with an anticipated short bottom time, but something bad happens on the bottom. You or your dive team becomes fouled, ensnared in lines. Or there is a partial cave collapse trapping you. The benefit of a rebreather over scuba is that it gives you time to sort out your problem. Gas consumption is not nearly as great a concern as with open-circuit breathing apparatus.

However, as the minutes tick by as you work deep to get yourself or a team member free, you might wonder, “How is my scrubber handling this depth?” In the middle of a crisis is no time to be making assumptions about the status of a major part of your life support system.

Ask your manufacturer how your canister performs at depth. You have a right to know, and that information just might prove useful someday.

The Positive Side of Internet Data Gathering

There is a good reason why God and aliens (of the extraterrestrial variety) use telepathy to communicate. It is the only secure form of information transmission. Everything else is subject to capture, storage, and retrieval.

There is currently a frantic paranoia spawned by national and international agency’s collection of virtually everything we say and do. The only thing not open for capture are our thoughts and dreams, at least for now. (Yes, the Army’s working on that).

But governments aren’t alone in information spying — commercial industry is perhaps outpacing governments in their data collection efforts. Their motivations may be different, but the frenetic pace and implications are every bit as invasive. Privacy, as we’ve known it, is dead.

I’ve previously written about Google Noodling , which is a way of catching Google in their data-mining efforts. And like the tone of that article, you have to take a lighthearted view of such efforts. It is not going away. And if we don’t “get over it”, we may, in my estimation, go a little crazy.

But there is a positive side to all this, and a large and growing number of people are finding this side to be personally satisfying. That has to do with family connections, or genealogy. I’ve written about that topic as well.

Scan20080_1 crop — My brother and I. He was five years older.

Last night I solved a very personal family puzzle through the help of Ancestry.com. Both my parents had brown hair and brown eyes. Both their younger children, sons, had blond hair and blue or green eyes.

I’ve spent a lot of time of late with my brother before he passed from a prolonged illness, and I was struck as never before with the purity of the blue color in his almost iridescent eyes. (I’m the one with the green eyes.) When young, both of us had blond hair, which eventually darkened with age. My brother was tall and thin. I was thin, but vertically challenged.

In the next generation, both my children have green eyes, perhaps because I married a green-eyed girl. Our daughter has blonde hair, and even a granddaughter has greenish-brown eyes. And a new grandson baby seems to have blue eyes and blond hair.

I have never ceased wondering, as did my parents no doubt, where those light colors came from. Having believed strongly in my mother’s fidelity, I kept assuming that someday I would discover the source of the blue/green eyes and blond hair.

That happened last night, thanks to the technology of digitization and data mining. I discovered a World War I selective registration document from my Grandfather who died in a hotel fire many years before my birth. At the age of 34 he had blue eyes and “light” hair. He was both tall and “slender”, pretty much a perfect description of my brother.

The next morning I was able to go through unidentified family photos, and there he was, identified at last, the Grandfather I never knew. So apparently it wasn’t the mailman after all!

Obviously this discovery is of interest to no one except my cousins and other relatives. However, it does point out the value of computers, computer databases, and the sharing of information that large databases make possible. There is a tangible reward, for both the company providing the product (the database) and the customers who benefit from the data shared.

I’m sure that when my Grandfather filled out his draft card in 1918, he had no idea that the digital image of that card would end up in the hands of his unborn grandchildren and great grandchildren 95 years later.

Which makes me wonder, what will the world know about each of us 100 years from now? We’ll be long gone, but the record of our existence will survive somewhere in the depths of a digital storage facility. Without a doubt our descendants will enjoy reading about the inane things which pleased or troubled us in 2013, and which we so freely posted thinking that no one was listening, and no one really cared.

Believe me, some people will care. And apparently, everybody’s listening.

The Day the Gorillas Were Stopped at our Door

I think one of the reasons I enjoy my grandchildren so much, and vice versa, is because they know they won’t always get a serious answer from me. They sometimes call me “silly”, but they do so with a smile. Silly is fun.

Children will assuredly get an answer to any question they ask me (within reason). However, that answer may be weighted more on the side of creativity and fantasy than on reality. They understand that, and delight in it. My instincts tell me that there cannot be too much fantasy during the playtime of young children.

As for my choice of an answer, it’s not at all a conscious decision to alter reality. I simply abhor an uninteresting answer, to anything.

Case in point: My five-year-old granddaughter found two bottles of the popular foaming adhesive, Gorilla Glue, next to our back door. “What are these for Granddaddy?”

Well, the stock answer would have been that I was gluing adapter ends to some polypropylene drainage gratings, and the Gorilla Glue would hold nicely until I could embed the gratings in concrete.

But I sincerely believe that if a writer can build on a play of words, he should. In fact, it’s almost an obligation of adults to pass on an appreciation of the joy of words.

So my answer to her was as follows: “I use Gorilla Glue in case gorillas come into our backyard to scare us. I’ll run out into the yard and glue their feet down.”

That answer was very well received.

“Why is one bottle white and one bottle brown?”

“Well of course the white gorilla glue is for white gorillas, and the brown is for brown gorillas.”

Silverback Gorilla at London Zoo, Wikimedia Commons

“Let’s go try it!” she yelled almost ecstatically.

Looking out the window I saw no gorillas, or any other animal wild or tame. “Well, I think the gorillas are hiding from us now.” Thinking like an adult, I didn’t want her to be disappointed.

“No, they’re not. We’ll just pretend,” she said with a sly wink that seemed to say, You do remember how to play, don’t you?

And with that, the five-year-old sprinted outside, paused at a spot where the threatening gorilla hoard was standing, and squirted pretend glue on pretend feet. She was fearlessly immobilizing at least six gorillas, and by my reckoning, three were white, and three were brown because she selected just the right bottle for the proper gorilla.

As proof of the effectiveness of her defensive strategy, no gorillas entered our house that day.

snowwhite — Snowflake the Gorilla, Wikimedia Commons

Now, to be fair to all gorillas, I do plan to take my granddaughter to the zoo one day and explain to her what an intelligent and peaceful, and threatened species gorillas are.

And then I’ll probably explain the real reason Gorilla Glue is named as it is. Gorillas undoubtedly use it to glue their nests together so gorilla babies won’t fall out of the trees at night.

Gorilla_nest (1) — Gorilla night nest. Photo courtesy of Jefe Le Gran, Wikimedia Commons.

Makes perfect sense to me.

The gorilla face featured photo is by Joshua J. Cotten on Unsplash.

Phytophotodermatitis and the Fig Tree from Hades

My fig tree is a diabolical, horticultural menace sprouted from a demon seed. I’ve tried to kill it, but it won’t die.

In general, I love trees, and figs, but this particular fig tree (Ficus carica for the Latin purists out there) has sorely offended me. It has attacked me, causing, as they say, bodily harm.

Fig Tree from Hell crop — My fig tree shortly after its attack. Looks innocent, doesn’t it?

And to top that, it doesn’t even produce edible figs. Some people call them goat figs, because only goats are undiscriminating enough to eat them. I’m guessing any goats eating my figs will be cursed — for eternity.

The conflict began like most conflicts, with an innocent encounter. I was using a water hose to tunnel under a concrete slab to install a 3-inch diameter drainage pipe. I then inserted a five-foot long piece of pipe. So far, so good.

But I decided I needed to replace that pipe with a longer, more flexible pipe, which promptly got stuck in the hole. Looking into the tunnel I’d made I saw that some relatively small roots were now in the way. I cut them with a lopper and then blindly inserted my left hand into the hole to help pull the pipe through.

It was a tight fit, and the back of my hand was grinding into the sand and the cut ends of the roots as I tussled with the pipe and finally pulled it through the hole. There was no pain associated with the sandpapering of my hand. But, as I later realized, I was grinding something toxic into the skin.

The next morning I looked at an irregular shaped red blotching on the hand. I assumed that the sandpapering from grinding against the sand grains had irritated the skin. But as time went on, the discoloration got worse, not better. A physician friend recommended a combined antibiotic and topical steroidal ointment, and bandages to protect the irritated skin. Dutifully applied for several days, that treatment resulted in absolutely no improvement. In fact, the discoloration seemed to worsen.

I continued to work on the drainage project outside, and, as it turned out, sun light seemed to make the discoloration worse.

A week later when irregular shaped blisters erupted, I realized that my skin had reacted to something in the sand, and the most likely candidate was fig tree sap from the roots I’d cut moments before inserting my hand.

The Internet revealed that fig tree sap was highly irritating to human skin. In fact, it appears to be an effective chemical weapon.

One Week Blisters — Warning: when magnified this looks pretty gross.

Quoting from AllAllergy.net, “Phytophotodermatitis is an acute skin reaction that may be easily confused with other causes of contact dermatitis. It is characterized by sunburn, blisters, and/or hyperpigmentation. The reaction takes place when certain plant substances known as psoralens, after being activated by ultraviolet light from the sun, come in contact with the skin. This report describes phytodermatitis due to contact with figs. (Watemberg 1991)”

Amazingly, the discoloration of my hand is still visible 6 weeks after the insult. But, I’m happy to report, that fig tree is not; visible that is. It was cut low to the ground. Eerily, it’s toxic sticky sap continuously coats the stump, so apparently that bedeviled fig tree is not entirely finished with its mayhem.

That sappy stump will, no doubt, be plotting a comeback this winter, out of pure botanical meanness. But I am firmly set on a plan of containment. Only time will tell whose chemical weapons are the more effective, the tree’s or mine.

Strangely, my war with the fig tree got me to thinking about art censorship. It’s true.

Most art devotees are aware of the stylistic device of placing a sculpted fig leaf in a strategic location to disguise the anatomical humanness of otherwise manly looking gods or athletes. Apparently, this form of censorship was foisted upon the art world by powerful religious prudes of the Enlightenment.

Two Weeks Fig Sap — Two weeks after exposure to fig sap.

Well, as I sulked about my long-lasting dermatological insult, I got to wondering; why would anybody even think of putting a fig leaf anywhere near what is arguably a sensitive part of the human body?

I strongly suspect that the artisans would not have deliberately incorporated fig leaves as part of their design, because they probably knew all too well just how irritating fig leaves can be.

I imagine Adam and Eve were both made rather uncomfortable by their leaves. Perhaps that was part of God’s revenge for their disobedience. Makes me wince to think of it.

But I digress. This current horror story ends like most horror stories; the foe fig is vanquished at the end. But just before the ending credits role, you catch a glimpse of the fig tree stump, still pulsing its hellish chemical weapons, and not at all fully dead. For all I know, it may already be planning its sequel, where it turns really nasty.

Lesson learned: I’ll be waiting for it, with gloved hands next time.

Cold Water Regulator Blues

It’s a black art, the making of scuba regulators for use in polar extremes; or so it seems. Many have tried, and many have failed.

Once you find a good cold water regulator, you may find they are finicky, as the U.S. Navy recently discovered. In 2013 the Navy invested almost two hundred hours testing scuba regulators in frigid salt and fresh water. What has been learned is in some ways surprising.

OLYMPUS DIGITAL CAMERA — Looking at a pony bottle that saved a diver when both his independent regulator systems free-flowed at over 100 feet under the thick Antarctic ice.

The Navy has been issuing reports on cold water regulator trials since 1987. In 1995 the Navy toughened its testing procedures to meet more stringent diving requirements. Reports from that era are found at the following links (Sherwood, Poseidon). (Here is a link to one of their most recent publicly accessible reports.)

The Smithsonian Institution and the Navy sent this scientist to the Arctic to help teach cold water diving, and to the Antarctic to monitor National Science Foundation and Smithsonian Institution funded trials of regulators for use in the under-ice environment. What those studies have revealed have been disturbing: many regulator models that claim cold water tolerance fail in the extreme environment of polar diving.

The Navy Experimental Diving Unit (NEDU) has developed testing procedures that are more rigorous than the EN 250 tests currently used by European nations. (A comparison between US Navy and EN 250 testing is found on this blog). All cold water regulators approved for U.S. military use must meet these stringent NEDU requirements.

Nevertheless, we learned this year, quite tragically, that the Navy does not know all there is to know about diving scuba in cold water.

For example, what is the definition of cold water? For years the U.S. and Canadian Navies have declared that scuba regulators are not likely to freeze in water temperatures of 38° F and above (about 3° C). (The 1987 Morson report identified cold water as 37° F [2.8° C] and below). In salt water that seems in fact to be true; in 38° F scuba regulators are very unlikely to fail. However, in fresh water 38° F may pose a risk of ice accumulation in the regulator second stage, with resultant free-flow. (Free-flow is a condition where the gas issuing from the regulator does not stop during the diver’s exhalation. Unbridled free flow can quickly deplete a diver’s gas supply.)

DSCN3524 — The regulator on the left free-flowed, the one on the right did not.

While a freshly manufactured or freshly maintained regulator may be insensitive to 38° F fresh water, a regulator that is worn or improperly maintained may be susceptible to internal ice formation and free-flow at that same water temperature. There is, in other words, some uncertainty about whether a dive under those conditions will be successful.

IsolatorValve1 crop — An isolator valve that can be shut to prevent loss of gas from a free flowing regulator.

That uncertainty can be expressed by a regulator working well for nine under-ice dives, and then failing on the tenth. (That has happened more than once in Antarctica.)

That uncertainly also explains the U.S. Antarctic Program’s policy of requiring fully redundant first and second stage regulators, and a sliding isolator valve that a diver can use to secure his gas flow should one of the regulators free flow. There is always a chance that a regulator can free flow in cold water.

A key finding of the Navy’s recent testing is the importance of recent and proper factory-certified maintenance. Arguably, not all maintenance is created equal, and those regulators receiving suspect maintenance should be suspected of providing unknown performance when challenged with cold water.

This finding points out a weakness of current regulator testing regimes in the U.S. and elsewhere. Typically, only new regulators are tested for tolerance to cold water. I know of no laboratory that routinely tests heavily used regulators.

Phoque_de_Weddell_-_Weddell_Seal — Weddell seal on the Antarctic sea ice. Photo copyright Samuel Blanc. (From Wikimedia Commons).

Considering the inherent risk of diving in an overhead environment, where access to the surface could be potentially blocked by a 1400 lb (635 kg), 11 foot (3.4 m) long mammal that can hold its breath far longer than divers can, perhaps it is time to consider a change to that policy.

About to descend through a tunnel in 9-feet of ice on the Ross Ice Shelf.

A huge Weddell Seal blocks the diver’s entry hole. He looks small here, but like an iceberg, most of his mass is underwater.

The Immigrants in My Backyard

I admit it; I have long been angry at the immigrants living in my backyard.

When I moved my family back to Florida over twenty years ago, I was thrilled by the sight of the beautiful green anoles (lizards) scampering over the white stucco walls of our house.

Green_Anole_Lizard — Green Anole, from Wikimedia Commons.

But over the years the native green lizards have all but disappeared, replaced by the drab brown lizards which immigrated somehow from Cuba and the Bahamas.

We can’t get Cuban rum or Cuban cigars, but we have Cuban lizards. How did that happen?

Anyway, it is a well proven scientific fact (see pages 12-28 of the linked publication) that when Cuban brown lizards move into a territory, the Green lizard population plummets. Part of the reason is because the larger brown lizards eat the young of native Green Anoles. That alone is enough to make me angry with them; although human anger is better directed towards human atrocities than against instinctive animal behavior. I know that, as a scientist, but still there is the annoyance I cannot quench at the loss of the Greens who, after all, belong here.

One particularly cold morning when the temperature had uncharacteristically dropped to 20° F overnight, I found a Brown Cuban Anole had crawled up to our front porch, trying, I suppose, to get as close to the house’s heat as possible. And there he lay, stiff and dead.

I actually rejoiced in the immigrant’s vulnerability. I remember thinking, “Bet it doesn’t get this cold in Cuba, does it? See, you should have stayed;” as if that frozen lizard had a choice in the matter.

As a matter of curiosity, and definitely not sympathy, I moved his stiff body out on the sidewalk where the warming sun rays were beginning to fall. I was thinking perhaps the local cats would like their lizard breakfast with the chill taken off it.

Imagine my surprise when I found 20 minutes later that the lizard was moving, and a few minutes after that, had managed to scurry off into the garden. Well, you have to admire toughness; and who doesn’t enjoy a surprise?

In the past couple of weeks these little guys’ toughness and their surprising lack of fear has helped me to appreciate these invaders, just a bit.

DSCN8030 — He’s hard to see; a good survival strategy.

I have been pushing my physical limits digging drainage trenches through root infested sandy soil. Much to my surprise, the Brown Cubans have been watching me, closely. Apparently my disturbance of the ground stirs up insects and small worms which the Anoles then feed upon with lightning quick forays into the digging zone.

What surprised me, however, is just how close they approach the digging. The most extreme example of lizard fearlessness was when I used a string trimmer to mow down ground-cover so I could uncover an outdoor sump pump. A Brown Cuban was hanging upside down on the stucco wall of the house, barely a foot away, with clippings from the cutter flinging at high speed into the wall where the lizard remained still but vigilant. He was completely unperturbed by the machine noise and the constant barrage of vine debris. Tough little critter, I thought.

Apparently, he had only one thing in mind; the prospect for the sudden appearance of food stirred up by the string trimmer.

During another phase of the project, what seemed like the same large Anole perched himself on any high elevation available so he could watch my digging. Every once in a while he would hop down into the disturbed dirt to snag a morsel, seeming unconcerned by the fact that a steel shovel was working the earth.

On one occasion he ran 18 inches or so right up to my foot to snag some insect I had failed to see. At the foot of the giant — yes, that little guy was fearless.

DSCN8021 — The Foreman lizard, keeping a watchful eye on my work.

OK, I had to admit, no Green Anole had ever done that before.

As I continued to work one hot Saturday, covered in sweat, I began to enjoy my constant companion. So much so that I picked up a camera and started taking photos of him, without the flash of course. I didn’t want to blind him.

On one shot the flash went off unexpectedly just inches from his face. He bolted. After 10 minutes or so, when he was nowhere to be seen, I actually felt bad, thinking that I’d scared him, or worse, blinded him. Yes, I know it was strange, that the Brown immigrant hater, me, actually felt remorse for my carelessness with the camera.

Finally, after another 30 minutes or so, he showed up again, as if nothing had happened. And with that, I felt forgiven.

Obviously, my hard attitude towards these immigrants has softened. The more time I spend with them, the more I appreciate their positive qualities: fearlessness, willingness to appreciate me as a food provider. They are in a word, opportunistic. And that, I believe, gives them an advantage over the more timid native Green Anoles.

As for the Cubans feeding on the natives? Well, they get as good as they give. Neighborhood house cats, who are certainly not native either, feed nightly on the Cubans. I cringe when I watch a cat flip an Anole, of any color, into the air and down it head first in a single gulp. That is the way of nature, and the fact that I like it or not has no influence at all on the outcome.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Keep Your Powder Dry, Rebreather Divers

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

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

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

Sofnolime 408 Mesh NI L Grade
Sofnolime 812 Mesh NI D Grade
HP Sodasorb (4/8 Reg HP)
Dragersorb 400
Limepak
Micropore

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

The lead photo is a sample bag of sodalime removed from absorbent buckets, awaiting testing.

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

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

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

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

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

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

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

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

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

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

What Are Spammers Thinking?

I’ve noticed that from time to time normal, rational people comment on my blog posts. Unfortunately, their comments are usually lost in the noise. Where is the noise coming from?

Well, spammers.

Spam on blog posts is one of the most bizarre human or computer behaviors I have ever seen. And frankly, it makes no sense at all.

When some computer fills up one or two paragraphs with wildly random characters or words, I think it’s a good bet that no intelligent life form is behind the keyboard. If I had a monkey, it could probably do a better job.

And though I appreciate it when some comments praise my work, when they quickly lead to an ad for Viagra I become suspicious that they aren’t actually insinuating that my posts are leaving the readers flat. I suspect they haven’t read a word, and some computer is inserting an ad which the programmer hopes will automatically get posted. I hate to disappoint, but my posts have nothing to do with the pharmacology of impotence, and therefore such obviously slanted ads will get no traction with me.

As a matter of fact, any reader with more than a microwatt brain will notice two things. 1) there are no ads on my site, and I strongly resist any outside efforts to get me to “monetize” my website. I figure if I can’t afford to keep the website up without selling ads, then I’ll shut it down. 2) The name of the blog strongly implies I am a man, and upon reading a few posts you see that I have an attraction to men’s toys. So why do I see a preponderance of spam trying to get me to push handbags and women’s boots?

If I was going to push ads, they would be for man-toys like motorcycles, airplanes, high definition video cameras, arctic survival gear, wingsuits, and diving gear. You know, guy stuff. But the purveyors of those specialty items have the good sense and integrity not to spam me. Fur-lined boots and handbags do not occupy even a cubic nanometer’s worth of space in my brain. So why would I link to spam sites selling those things?

You would think that the fact that I have dumped thousands of spam attempts for completely unnecessary fashion accessories would catch someone’s attention in the respective marketing departments. Their money is being wasted. But that fact is seemingly never appreciated by the spammers.

Also not appreciated is that I never publish anything in Japanese. I have been to Japan, but I can’t read or write kanji or hiragana. In fact, one of the most disorienting experiences of my life occurred in a Japanese bus station where there was not a single character from the Latin alphabet. So why would spammers send me lengthy spam in Japanese writing? Are they completely clueless? Or do they think I’m a renaissance man who acquires languages like some people acquire DVDs? I’ll confess, I’m not that man. I have a hard enough time with American English.

The irony of it is that before long I’ll likely receive one or more spam comments based on this posting. It will probably read something like this:

“You hit the actual fingernail in the head regarding this gleam… This information is so hard to find I will link to your feed and tell my friends who have been searching. Buy Viagra cheap online.”

How about that for a non sequitur!

If you have an interest in the psychology of spammers and spamming, there are a couple of articles, one scientific and one lay press that I can recommend. Another article, classified by Google as being scholarly, reportedly has a bad habit of infecting computers with viruses and other malware. According to the recommendations of my security software, I will not be recommending that site.

Spammer Image Photo by Clint Patterson on Unsplash

Last Man Standing

It seems ironic that at the same time that equality of the sexes in marriage is being heavily promoted, there is a scientific announcement that the male of the human species is anything but equal; we are genetically weak. According to at least one female scientist, human males are destined to die out due to the fragility of our single Y chromosome.

This grave announcement comes from none other than the aptly named Professor Graves, of Australia.

Her forecast got me to thinking; what if I was the last human male on Earth. What would life be like?

My first naive, and probably delusional impression was that I would inevitably become a hot item. It really wouldn’t matter what I looked like; I would be desirable simply because of my rarity.

Which, if true in a fantasy sort of way, could actually be a nightmare. I would surely not be attracted to ALL females. I mean, that covers a pretty wide territory. The human population is pretty diverse.

However, once you become that unique of an entity, perhaps your free will may go out the window. It may not matter what I want. For instance, becoming or remaining paired with a single lady, remaining monogamous, might itself become a fantasy.

But as I delved a little deeper into this musing, another possibility presented itself. A world without men could only exist if scientists figured out a way to keep the population going without men. I suppose it’s possible, in an artificial sort of way. So what would I be then?

Well, perhaps nothing more than a freak, a rare oddity with a bizarre anatomical abnormality. Is it reasonable to expect genetic deviants to be in great demand by the ladies? I think not.

So, I hope that the scientist who claims that men may die out due to their chromosomal vulnerabilities is wrong. If not, the psychological outlook of that declining population of manly men would probably be bleak. And certainly, if by accident of birth I were the last man standing, my life experience might be every bit as challenging as it is for those with rare congenital handicaps.

Knowing that, I feel sure that if the scales of male/female birth ratios begin tipping away from the current normality, some male-dominated government will fund extensive research aimed towards preserving the status quo. Ironically, the answer to whether that research would be fruitful or not, might already be written in our genetic code.

As they say, only time (five million years by Professor Graves’ estimate) will tell.