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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 04/26/2007 : 16:07:42 [Permalink]
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quote:
Originally posted by Dr. Mabuse
The buoyancy depends of the weight of the displaced water, and since water in rather incompressible, they buoyancy would not differ from Earth.
(edit spelling)
Yeah, that's true. I meant that pressure (not compression) would increase dramatically faster than on earth as one submerged in an ocean. My context may have been confusing, as I was dealing with pressure gradients for both atmosphere and hydrosphere, while not dealing with the matter of compression in water.
I read 20,000 Leagues Under the Sea as a kid. Jules Verne had Captain Nemo's suited hydronauts breathing air that was compressed almost infinitely. Verne apparently wasn't aware that it would liquify at some point, and become, like water, almost incompressible after that point.
With geological processes working in 2.22 gees on the "new" planet, I would expect a smoother surface than on Earth. Also the sensible atmosphere, even if it might be more dense overall, would be more concentrated at the surface than on earth. This might also mean there would be more light elements such as hydrogen on the planet (mainly in the form of water), as less of the more volatile gasses could escape into space. Sort of an inverse of the situation on Mars.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
| Edited by - HalfMooner on 04/26/2007 16:09:22 |
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Chippewa
SFN Regular
USA
1496 Posts |
 Posted - 04/26/2007 : 16:29:18 [Permalink]
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quote:
Originally posted by beskeptigal
...I'll wait till they get the spectrograph revealing the composition back before getting too excited.
Its far too faint for spectrography and the White House and Congress killed NASA's Terrestrial Planet Finder project. So it might be a long wait.
quote:
beskeptigal
The real discovery here is we have found the first planet that isn't a gas giant. The fact it is orbiting a red dwarf star allowed it to be detected while only larger gas giants can wobble larger stars enough to be detected so far.
Yes, that's really cool! |
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beskeptigal
SFN Die Hard
USA
3834 Posts |
Posted - 04/26/2007 : 21:39:05 [Permalink]
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I know it's too faint for today's instruments. I was thinking ahead.  |
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Dave W.
Info Junkie
USA
26020 Posts |
Posted - 04/27/2007 : 07:11:52 [Permalink]
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quote:
Originally posted by HalfMooner
I meant that pressure (not compression) would increase dramatically faster than on earth as one submerged in an ocean.
It ought to be more-or-less linear, at least near the surface, with the increase in gravitational strength. On Earth, a column of water nearly 34 feet high and one inch square weighs the same as an inch-square column of air from the surface to space (on average). So the water pressure 34 feet below the surface is two atmospheres - one for the actual atmosphere, plus one for the weight of the water. Every 34 feet down adds one more atmosphere of pressure. Roughly, you can calculate the pressure in pounds-per-square-inch as your depth divided by 33.93, multiplied by 14.7, plus 14.7.
Because the gravity on 581 c is 2.22 times stronger, you could calculate the water pressure as your depth divided by 33.93, multiplied by 32.6 (14.7 times 2.2), plus whatever the atmospheric pressure is at sea level there (lots of factors might go into that). The point is that the weight of the water goes up linearly with gravitational strength. The weight of the atmosphere above the water is a constant (a constant that we don't know, but a constant nevertheless), and so will quickly be "swamped" by the weight of the water as one goes deeper.
So, the increase wouldn't really be "dramatic." Assuming the same amount of atmosphere as we have on Earth, then whatever your depth on 581 c, you'd have to dive 2.222 times as deep on Earth to match the pressure. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 04/27/2007 : 07:20:18 [Permalink]
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What I'm warning about is valid, Dave. It's all about diver safety. A dive that would be safe on earth might be deadly there, so be careful! Better to begin warning people now than too late.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
| Edited by - HalfMooner on 04/27/2007 07:20:43 |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 04/27/2007 : 07:48:12 [Permalink]
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quote:
Originally posted by HalfMooner
What I'm warning about is valid, Dave. It's all about diver safety. A dive that would be safe on earth might be deadly there, so be careful! Better to begin warning people now than too late.
As an ex-Navy diver, I shudder to think of what the decompression tables would be like. If, that is, the oxygen percentages were low enough to allow any but the shallowest underwater work at all.
Heh, at 200 feet in our oceans, the air gets almost thick enough to chew. You might not be able to breath at all much below a few atmospheres depth.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist! 
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Hawks
SFN Regular
Canada
1383 Posts |
Posted - 04/27/2007 : 15:22:44 [Permalink]
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quote:
Originally posted by filthy
...I shudder to think of what the decompression tables would be like.
It should allow you to do longer or deeper dives since the relative difference in pressure at any depth compared to the surface will be smaller on that planet relative to Earth. It's decreasing pressure at the surface we should be worried about, not increasing. Assuming we're talking about the bends that is. If we are talking about oxygen concentration being the problem, then it follows that since oxygen gets poisonous at roughly a partial pressure of 1.4 that you shouldn't descend to more than about 50 metres (assuming a 20% oxygen concentration in the air being breathed). That is way deeper than your average PADI Open Water Diver would go. If we are talking about nitrogen narcosis being the problem, then that should kick in about 10 metres shallower than here on Earth - for the average person at about 20 metres. |
METHINKS IT IS LIKE A WEASEL
It's a small, off-duty czechoslovakian traffic warden! |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 04/27/2007 : 18:53:13 [Permalink]
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Hawks said:
quote:
If we are talking about oxygen concentration being the problem, then it follows that since oxygen gets poisonous at roughly a partial pressure of 1.4
pO2 of 1.4 to 1.6 is ok for exposure times under a couple of hours. The PADI and NAUI dive parameters are just very conservative. For good reason, since most people lack common sense.
You won't see rapid toxic effects until you get to about pO2 2.0 to 2.2 or higher. And even then the exposure time to serious neurological impairment varies by individuals, probably in proportion to your own ratio of lung capacity:body mass.
NOAA, and many of the dive training people (PADI, NAUI, SDI, IANTD) recommend a max O2 single exposure limit for recreational dives of pO2 1.6 for 45 minutes. It is a conservative limit designed to make it difficult for people to harm themselves while breathing gas under more than 1ATM of pressure.
filthy said:
quote:
Heh, at 200 feet in our oceans, the air gets almost thick enough to chew. You might not be able to breath at all much below a few atmospheres depth.
Divers have used open circuit SCUBA to depths over 1000 feet (1082 feet, or 330m, is the current record for open circuit, thats 32+ ATM on earth). As long as the breathing gas is delivered at ambient pressure, there shouldn't be much trouble breathing it in.
My deepest dive is ~310ft salt water on a CCR. Have several to 200ish feet on CCR, many to 150ft+ on open circuit, and have never had a real issue breathing.
But I know what you mean. You definitely notice the increased density of your air. No idea what the upper limit to breathing gas density is though.
Half said:
quote:
What I'm warning about is valid, Dave. It's all about diver safety. A dive that would be safe on earth might be deadly there, so be careful! Better to begin warning people now than too late.
Converting dive tables would be pretty simple. You could use the same ones, just get a depth gague that runs off ambient pressure (as most do), and follow the tables as if you were at an earth equivilent depth based on ambient pressure.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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Dave W.
Info Junkie
USA
26020 Posts |
Posted - 04/27/2007 : 21:46:49 [Permalink]
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quote:
Originally posted by Dude
Converting dive tables would be pretty simple. You could use the same ones, just get a depth gague that runs off ambient pressure (as most do), and follow the tables as if you were at an earth equivilent depth based on ambient pressure.
Good point. Bring an Earth-calibrated depth guage and Earth dive tables. If the guage says you're 25m down, do what you're supposed to do when you're 25m down on Earth. Sure, you'll only be 10m down (or so) on 581 c, but if you ignore the guage and tables, you'll wind up dead.
Pressure is pressure, doesn't really matter how fast it increases with depth.
Well, within reason. On a planet with gravity 14 times stronger than Earth's, if your body were vertical in the water, there'd be more than a one-atmosphere difference in pressure between your toes and your head, which I imagine might wreak havoc with your circulation. Of course, if you were on a 14-G planet, you'll probably have such big problems to deal with that taking a dip would be the lowest of your priorities. And the last thing to go through your mind would be your shoelaces. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Hawks
SFN Regular
Canada
1383 Posts |
Posted - 04/28/2007 : 01:55:57 [Permalink]
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quote:
pO2 of 1.4 to 1.6 is ok for exposure times under a couple of hours. The PADI and NAUI dive parameters are just very conservative. For good reason, since most people lack common sense.
Yes, that rings a bell. A partial pressure of 1.4 for oxygen was the level considered safe (as opposed to poisonous). Crikey, how many divers are there around here? |
METHINKS IT IS LIKE A WEASEL
It's a small, off-duty czechoslovakian traffic warden! |
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Siberia
SFN Addict
Brazil
2322 Posts |
Posted - 04/28/2007 : 09:36:27 [Permalink]
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| Y'know, reading about all the speculations on Gliese c, it makes me think... it sounds a lot like the planet where the creations of my brain live... |
"Why are you afraid of something you're not even sure exists?"
- The Kovenant, Via Negativa
"People who don't like their beliefs being laughed at shouldn't have such funny beliefs."
-- unknown
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 04/28/2007 : 14:48:13 [Permalink]
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Hawks said:
quote:
Yes, that rings a bell. A partial pressure of 1.4 for oxygen was the level considered safe (as opposed to poisonous). Crikey, how many divers are there around here?
Its a popular hobby.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 04/29/2007 : 03:30:49 [Permalink]
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Apart from a little spearfishing and lobster-snatching, using a snorkle & glove, I have never dived for sport and even dislike SCUBA (can't get heavy, dig your ass into the mud and swing a hammer with SCUBA). I look at it from the perspective of a working, hardhat diver qualified in helium. My deepest was when I was aboard the USS Holland,a Submarine Tender, and got sent TAD to a Submarine Rescue Vessel (forgotten the name of it -- mighta been the USS Hummingbird) to search for the lost H-bomb off Spain in, I think, '65. I, and others, made a couple decents to a little over 400'. They decompressed us in recompression chambers on the surface and did it with the slide rule. Looking back, I marvel that any of us survived. The miniture submarine "Alvin" found the bomb.
That was the job that Carl Brashear got hurt on, and as I recall, his was the only, serious injury.
If memory further serves, we were using a 16% oxygen mix. We were brought to 50' with the usual, helium tables, then had a half hour decompression stop on O2, and then were yanked out, stripped in record-setting time, and tossed into the chamber. Believe it or not, I had a tooth explode during a decompression sequence, coming up from the 50' stop.
It is my understanding that the decompression tables used in my day have been considerably revamped, and I have no idea what they are today. But never the less, I think that a dive to any moderatly serious depth on this planet would require something like the JIM suit to keep from killing yet more divers.
Y'know, I'd really like to try a JIM suit out, someday.....
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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| Edited by - filthy on 04/29/2007 03:38:16 |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 04/29/2007 : 13:36:17 [Permalink]
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filthy said:
quote:
It is my understanding that the decompression tables used in my day have been considerably revamped, and I have no idea what they are today. But never the less, I think that a dive to any moderatly serious depth on this planet would require something like the JIM suit to keep from killing yet more divers.
Yeah.
Navy dive tables are often the gold standard though. You'd be amazed at the lack of legit research that goes into some deco protocols.
Most tech diving (not industrial, but sport-tech) tables use the navy tables as a reference.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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| Edited by - Dude on 04/29/2007 13:38:30 |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 04/29/2007 : 14:51:56 [Permalink]
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quote:
Originally posted by Dude
filthy said:
quote:
It is my understanding that the decompression tables used in my day have been considerably revamped, and I have no idea what they are today. But never the less, I think that a dive to any moderatly serious depth on this planet would require something like the JIM suit to keep from killing yet more divers.
Yeah.
Navy dive tables are often the gold standard though. You'd be amazed at the lack of legit research that goes into some deco protocols.
Most tech diving (not industrial, but sport-tech) tables use the navy tables as a reference.
The old Navy tables worked. If anything, they tended to err on the safe & conservative side. But if you had to drop back down to 165' on a Table 4 due to another hit on Table 3, you start wondering if you shouldn't apply for residency. This happened to me when I was chamber-tender for another diver who had an oxygen hit. We were a good way into the 10' stop (the loooong one) when the corpsman with us got somewhat bent (joint pain). This happened at the Experimental Diving Unit in Bethesda, MD.
Between medical checks, we played dime-a-game, penny-a-point, round-robin cribbage through the whole thing. I lost something like four bucks and learned to hate cribbage.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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Earthlike planet
