For Relax Max: Pressure Breathing

Relax Max asked: Finally, is this the same reason high altitude fighter pilots have to concentrate on forcing the air out of their lungs when they are breathing pressurized oxygen/air, or is that an old-wives tale?

Nope, not an old's wives tale - it's a real necessity. Depending on the type of oxygen mask, aviators may need to learn to pressure-breathe.

You see, in normal pressure, we breathe in and out by expanding and contracting our diaphragm, increasing/decreasing the size of a pocket of air inside our bodies, creating a high pressure (exhale)/low pressure (inhale) condition relative to the outside air. Are bodies tend to be tolerant of quite a range of air pressures as long as the partial pressure of oxygen doesn't drop below certain levels or get above certain levels. We can condition our bodies to be even more tolerant., but those tolerance levels have limitations.

Once the outside pressure drops below a certain pressure we need higher concentrations of oxygen, up to and including 100%. This situation is made worse by the fact that a certain portion of air in our lungs doesn't get expelled. As the pressure drops, that portion that doesn't get expelled (and therefore is new air that doesn't come in) takes up more and more volume until, even with 100% oxygen, there isn't enough "new" air for me to survive.

In that case, pressurized oxygen is used. For the type of mask in question, the ambient pressure is higher than ambient, making inhalation easy; however, unless the "used" gas is expelled, you can't inhale again. In this case, you're pushing against a greater pressure than the rest of the body is exposed to. Hence the difficulty.

Fun stuff.

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For Relax Max: Terminal Velocity

Relax Max continued: If I may have two questions, the second is about terminal velocity. If a large object (a passenger airliner, say) reaches terminal velocity before impact, do smaller (or more aerodynamic) objects whose terminal velocity are higher (I assume) "pass" the airliner on the way down? Or does everything hit the ground at the same time?

Good question(s). As you asked, items don't have the same terminal velocity. The maximum speed an item attains in air depends on many different factors. Surface area, fluid factors, and mass are key factors, but other factors include roughness, shape, initial speed, etc. A man falling, for instance, can change his terminal velocity drastically between falling spread eagle and pulling his limbs in and falling headfirst (as skydivers do to move up and down relative to each other). A man can't change it enough not to be going too fast for landing without a parachute, but that's a different post.

Terminal velocity is effectively the speed an object obtains when the force of gravity is canceled by the opposite drag on an object so that it stops accelerating. If gravity were not involved, there'd be no terminal velocity because drag would just work to make things go slower with no counterforce. (Newtonian physics I can explain if you'd like). Initial velocity makes a difference because it adds a factor beyond gravity (and velocity has an effect on drag).

A debris field is determined by multiple factors as well: initial speed, what caused the initial breakup, and how much and what kind of debris is generated. A biplane, for instance, that lost it's rudder might have a very limited debris field, where as Columbia's debris field extended over several states. Explosions (whether combustive or pressure built) send debris forward and backward, extending the debris field. Flat low mass debris will fall slower that compact debris.

So, to answer the last, everything doesn't land at the same time - except in a vacuum as they demonstrated on Apollo 15.

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For Relax Max: "Explosive" Decompression

Relax Max asked: I'm researching an article on high altitude airplane collisions in which the integrity of the pressurized passenger cabin is suddenly compromised. I would like a more detailed explanation on the term "explosive decompression" than I am finding on wikipedia. I'm guessing it means the person can't expel the air in his lungs fast enough and so his lungs explode. Probably preferable than living two minutes before he is killed by impact with the earth. Is that what it means?

No. I've talked before about decompression on Rocket Scientist. In general, with regards to high altitudes, the effects of high altitude alone is insufficient to cause any part of a person to "explode." When movies show eyes popping out of the head or body's spontaneously exploding in vacuum, well, it's just not real. Explosion, per se, is not going to happen (unless someone insists on holding their breath). A single atmosphere is just not enough differential pressure to tear a body apart. Usually, when experts think of explosive decompression, it's a deep sea situation instead, where differential pressure can be many atmospheres instead of one and such horrible events as the Byford Dolphin calamity are possible. (Read with caution; it's gruesome)

When people describe "explosive decompression" with regards to high altitude, they are talking about the plane, not people, experiencing a pressure differential it is not designed to withstand. Not to say low pressure doesn't have effects on people. Anoxia is quite debilitating and harder vacuums can swell body parts as they did for Kittinger when during one of his high altitude balloon jumps. High enough, and the saliva can boil in one's mouth. One can be subject to the bends as a result of sudden high altitude and some forms of lung trauma or altitude sickness.

When I was a test subject, we actually trained through a simulated instance of rapid decompression, complete with fog and tests to see our reaction (and how long it took symptoms to show up) for anoxia. Great fun, that.

Decompression, however, is not a guarantee of a crash, depending, of course, one what caused the decompression. There's a nice little table in Wikipedia that lists notable aircraft incidents involving decompression. Though many ended badly, a surprisingly high number involved few if any casualties. Often the most dangerous results were debris affecting engines or stress destroying control or hydraulic lines. The pressure differential can be acerbated by the high speed of a plane so that, even after the plane's pressure has equalized (which rarely takes long), there is still a suction issue because high speed air (like that flowing outside a rapidly flying plane) is at a lower pressure than still air (like that inside the plane). It is, in fact, this differential pressure between fast and still air that allows a plane to fly by providing lift.

Additionally, anything that might extend outside the plan, like, say, a limb, will produce drag in that swiftly moving air and tend to yank the object out for aerodynamic reasons. And that ties nicely into your next question.

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For Shakespeare: Asexual Reproduction

Shakespeare asked: Also, my daughter has a question, sparked by our birds and bees talk: Is it possible for a person to have a child without sperm and egg coming together? Why or why not? Has it ever happened, or might it become possible in the future?

There are critters out there that manage to reproduce without male involvement. The primary process is called parthenogenesis and it's not a common function. In general, particularly in the higher animals, sexual reproduction (sperm and egg type fertilization) is more advantageous for genetic diversity. Under general circumstances, an ovum, the egg as it were, contains only half the genetic material necessary for a new creature. Humans, for example, have 26 pairs of chromosomes, with each parent providing half of that pair. Without fertilization from a sperm, it isn't viable.

But there are exceptions. Aphids, for example, are capable of reproducing from a single female, no male. Most of the time, these aren't clones but rather combinations of eggs together so that it contains mixtures of pairs just like the mother and pairs of chromosomes that are identical. Usually, the results are always female (if males are determined by an XY configuration). This and related processes are not restricted to insects, though the vast majority of animals prone to this are insects and other invertebrates, but it's been seen in lizards, birds and even sharks.

There's even a parasitic bacteria that can cause it in insects.

It has not been observed in mammals; however, it can be artificially triggered several mammals and it can cloning are theoretically possible even for humans.

Multiple generations from a single genetic source, however, can be very dangerous. Frequently, complex animals have "bad alleles," recessive traits that can be deadly or debilitating if they manifest. Because they are so destructive, they are rare enough that creatures rarely have an offspring with both - thereby preventing manifestation (as "anything else" is dominant). If, however, one starts duplicating chromosomes as pairs, the chances of having a bad allele manifest increase sharply.

I have to tell you, I'm still fond of making offspring the old fashioned way.

If the Mother shows up, she'll probably correct my answer in a dozen ways and can probably expand it as well.

(She also asked: BTW, where do I get one of those novel progress thingies? I want to put one on my own blog... since I'm now actually working on something. Here are some sources:
http://www.nanowrimo.org/eng/widgets
http://languageisavirus.com/nanowrimo/word-meter.html
http://www.writertopia.com/toolbox/meters)

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For Boris: Writing Mary Sue

Boris said: As a writer, do you struggle with Mary Sue? If you are unfamiliar with the term, it arose from fan fiction, and means more or less that the writer will identify with the main character to such a degree that she/he will ultimately give more and more power to said character, until the story devolves into some kind of wish-fulfilment fantasy. Rampant in fan fiction of course, but professional writers have been known to fall prey to Mary Sue as well (coughLaurellKHamiltoncough). In my (very) limited experience as a writer, I have found that this can be a problem for me too, especially when writing in first person. Do you or your husband have the same problem? Who acts as the voice of reason?

This is a very interesting question, one that does not lend itself to a simple answer. At least with me. I did have to look up the term "Mary Sue" to get better definition so I could answer the question appropriately.

I don't write fan fiction. I do write fiction, particularly speculative fiction where magic and skills are quite common. I also tend toward larger than life characters. That tends to go with the territory, too. Additionally, I do identify with my characters and always have.

So, am I prone to this? Actually, I don't think so. First off, although I'm usually the seed of my characters, what I generally do is take a few of my traits and build a new characters with a different background. I play, what if someone with X,Y,Z traits was raised in this environment. I love what if. By the time I've tweaked this and that to fit the environment and the background, I usually discover that this character, based on me, is completely different from my other characters, even though they are also based on me. They have to have limitations (generally different ones than I do) because a character must have balance. Nothing I personally hate more than a character that can do no wrong, make no mistakes, never lose. They have to grow.

Many of male characters are actually a hodge-podge of characteristics that appeal to me. They tend to be funnier, though I'm not sure why. I love my male characters. But they have to have limitations, too. They can't be good at everything, never fail, never falter, either. I often have ensemble casts so that different people can bring their particular skills into play.

If I have a character that's "too good to be true," for instance, like Xander, my shapeshifter/telepath who can turn into a dragon, I make him insecure from mistreatment growing up, positive that his dragon nature makes him prone to violence. He doesn't trust himself and takes control to an extreme to overcompensate. And, under it all, he's human, which is why I'm giving him meningitis in the second book, making him inadvertently hurt the woman he loves.

I do that because he has to be limited. He can't be perfect. And, I admit it, it's my doing. My husband is more superhero prone. For instance, I wanted to give him PAM (amoebic meningitis and cure him via magic) but Lee absolutely couldn't stand the idea of parasites in him. But he'd tolerate a virus so that's what we did. So, Xander, star and nearly single-handed savior of the first book, is out for the count (as well as his healer girlfriend) in this one so all the rest have to find solutions without him.

Do I do wish fulfillment? Yes and no. Sure, it's fantasy and we play what if, if that's not living out wish fulfillment, I don't know what is. I also put my characters through things I'd never want to live through myself, with pain and hardship I wouldn't wish on an enemy.

For me, that's balance, good with the bad, responsibility with the power.

On the other hand, I'm hardly objective. :)

Update: I asked my husband. He said I didn't have a problem with it, that I was always adding imperfections and ruining their badassedness. He didn't say it like he approved either, so I'm clearly the one who keeps it from happening.

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For Max: The Problem with Statistics

Sometimes, they just don't mean anything.

Update: This had been emailed to me without attribution. Thanks, Boris, for letting me know the chart is from here. There's a damn fine letter at the link worth reading, too.

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For Aron: What About the ISS?

Aron said: I've also been curious because of commerials for Discovery's The Colony...what would NASA do about the ISS if it was real.

Can't answer that absolutely. First off, the cataclysm of "The Colony" has never made much sense to me. Also, I found the show stupid (personal opinion) - they're priorities often seemed whacked. Was it supposed to be some sort of disease that wiped most people out worldwide?

Well, what we would do depends on the problem. If NASA, the landing facilities, our launching facilities or the Mission Control facilities were completely compromised, we'd bring down our crew as soon as practical unless we had reason to think the problems were temporary.

However, we're not the only ones with access to ISS (as demonstrated after Columbia). If the cataclysmic issue were not one for Russia, they might choose to continue to use ISS or we might find some way of working with them so we could maintain a foothold there. But, if our facilities/abilities/etc. were compromised, we'd be in a poor bargaining position to demand much. They'd hold all the cards.

What we couldn't readily do is take it apart or bring it back down. Provisions are not in place for either option right now and it would take a great deal of effort and planning, as well as considerable resources, to do so. If someone wanted to use it, they would have to reboost because it would eventually come back in uncontrolled if abandoned permanently.

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For Aron: What Went Wrong?

Aron asked: One more...How does my AIAA Design/Fly/Build team avoid this from happening again the plane flew before, but it got damaged during take off. What sort of tests should we do?

Sorry I've taken so long to look at this, Aron. Wow, you're expecting me to figure out a great deal from a video. I'm also not technically an aerospace engineer in that I've never designed a plane. I'm sure you have great resources there to draw from. But, since you asked me and I am nothing if not opinionated, here's what struck me.

The problem does not appear to be the landing gear unless it was broken before you tried the first run. If it was and that's why it kept going lopsided, strengthen the gear and move on.

However, if, as it seemed, it was the repeated lopsided runs that eventually damaged the landing gear, there are a few possibilities that come to mind. First and, to my mind, most likely if the wings house the fuel tanks as they do in many planes, the tanks might not have been filled equally, throwing off the center of gravity to one side. If the center of gravity was off, this would cause turning even if the thrust from the two engines were the same. Or, if the c of g was fine, it might be that the thrust from the two engines was unequal, either a deformation of a propeller perhaps or an engine problem that let one spin at a different spin than the other.

It might also have been control surfaces out of sync (say flaps on one wing, but not the other) or a rudder turned the way it shouldn't be. It might be a deformation of one wing that changed wind resistance or lift from one side to the other or an incipient imbalance in the landing gear that went unnoticed.

Without data, the fuel inequality or control surface problem might not be detectable unless they are design issues (i.e. if they were operator error). However, a problem in the fuel tank that prevents equal filling or causes a control surface to stick my be detectable with testing.

Given the dearth of data, that's the best I can offer.

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