Water Streams in Space - ^

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Post by isoaker » Sat Jul 02, 2005 5:40 pm

The following is a bunch of moved posts that began in the 'cps homemade' thread. I've only removed the parts from the original thread concerning this topic.

From Frankenbike (June 30):
So if you were in outer space, and you fired a stream of water out of the space shuttle, it would immediately vaporize?

From Aquarius (July 1):
frankenbike wrote:
Aquarius wrote:

So if you were in outer space, and you fired a stream of water out of the space shuttle, it would immediately vaporize?

Since the space shuttle doesn't go beyond earth orbit, the approximate temperature outside it when orbitting would be about -269 degrees C. Water freezes at this temperature, at any pressure. It in fact forms what is referred to as Ice-Eleven or Ice-XI, a very low temperature form what we put in our cold drinks.

This would actually be a neat process, as the instantly frozen water would travel virtually at the same velocity at which it was fired until an outside force acted on it, all while orbiting of course.
:suspicious:

From iSoaker.com (July 1):
^ though cold, as there is extremely low atmospheric pressure at the altitude of the shuttle, it still may be warm enough to boil the water (though I'm not 100% sure about that). There'd be an interesting balance between water cooling upon exiting the nozzle, the desire for water to boil since there is almost no atmospheric pressure, and the rate at which water froze due to the low temperature. Heat capacity versus thermal loss versus boiling point depression... my head hurts.

From Aquarius (July 1):
isoaker_com wrote:^ though cold, as there is extremely low atmospheric pressure at the altitude of the shuttle, it still may be warm enough to boil the water (though I'm not 100% sure about that).

Orbitting the sun maybe. Around Earth however, -269 C is far too cold. Take a look at a phase chart for water. You'll notice that at around -78 C or lower, water exists ONLY in solid form at ANY pressure. You could shoot near boiling water and it would make little if any measureable difference.

From iSoaker.com (July 1):
Take a look at a phase chart for water. You'll notice that at around -78 C or lower, water exists ONLY in solid form at ANY pressure.

Ok.. my bad for poor description of my thoughts. Yup, water when it's cold, is solid. However, there'd be a transition time between the pressurized water leaving the nozzle and the time it takes for it to freeze. Assuming the nozzle doesn't get clogged, would the water chill fast enough to become a solid stream or would it boil first, thus freeze as spreading mist particles? Of course, this is really off topic. :goofy:

:cool:

From Aquarius (July 1):
isoaker_com wrote:Ok.. my bad for poor description of my thoughts. Yup, water when it's cold, is solid. However, there'd be a transition time between the pressurized water leaving the nozzle and the time it takes for it to freeze.

Sure, and the warmer the water originally the longer it would take for it to freeze. This would only be fractions of seconds though.

Assuming the nozzle doesn't get clogged, would the water chill fast enough to become a solid stream or would it boil first, thus freeze as spreading mist particles?


This would depend alot on the type of nozzle used. A laminar stream would render rigid, though broken, columns of ice. An aquastorm type nozzle would make droplets of ice, with a riot blast making an assortment of frozen droplets, chunks, and ice "vapor".

Of course, this is really off topic. :goofy:


Maybe not. Wasn't Super Soaker's inventor a NASA engineer at some point?

From iSoaker.com (July 1):
Maybe not. Wasn't Super Soaker's inventor a NASA engineer at some point?

Uh.. this thread is about building a homemade CPS system, not soaker or water physics in general. :goofy:

As for columns of ice from a laminar flow, I'm not so sure that'd necessarily be the result. For sake of argument, I'd place the starting water at 4C (cool to us, but much warmer than ambient orbital temperature). Suddenly dropping both external temperature and pressure, part of me would say there could be an intial boiling event since the heat-capacity of water would prevent it from suddenly freezing, but at that pressure, it'd still be warm enough to boil. Everything would be occurring in fractions of a second timescales, of course, but it may be enough to ruin the laminar flow of the stream, thus making it spread a lot more after exit from the nozzle than it would if it were just that cold, but pressurized at 1 atmosphere.

:cool:
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Post by isoaker » Sat Jul 02, 2005 5:43 pm

From Aquarius (July 1):
As for columns of ice from a laminar flow, I'm not so sure that'd necessarily be the result. For sake of argument, I'd place the starting water at 4C (cool to us, but much warmer than ambient orbital temperature). Suddenly dropping both external temperature and pressure, part of me would say there could be an intial boiling event since the heat-capacity of water would prevent it from suddenly freezing, but at that pressure, it'd still be warm enough to boil.


If pressure dropped exponentially faster than temperature, yes. If the water was heated and pressured to near supercritical before firing, possibly. In either case it wouldn't be boiling as we know it--moreso explosive vaporization. But we're talking regular old water going from standard temperature and pressure to a near absolute zero vacuum. Its more like extreme flash freezing. Water will expand, but to form ice, not boil or vaporize.

Everything would be occurring in fractions of a second timescales, of course, but it may be enough to ruin the laminar flow of the stream, thus making it spread a lot more after exit from the nozzle than it would if it were just that cold, but pressurized at 1 atmosphere.


It would be an interesting experiment. I don't believe the laminar flow would be interrupted, but that semi-frozen column integrity would suffer as water in the interior of given volumes froze and expanddd against that surrounding it. This expansion induces cracks that cause breaks. Its the reverse of ice cracking when you pour a warm drink over fresh, cold cubes.

From iSoaker.com (July 1):
Water will expand, but to form ice, not boil or vaporize

That's the thing. Water expands to form ice only if it is given enough time to form the ice lattice. If it can be chilled quickly enough, it'll form a glass state (i.e. no ice crystals formed), thus have no expansion. I actually do a lot fo freezing of liquids in liquid nitrogen and vapour nitrogen streams and hit them with X-rays to check for the presence of ice. Simply plunging water into liquid nitrogen (even small volumes ~10uL or so) still yields ice formation despite the quick heat transfer. Larger volumes definitely form ice. Thing is, all this is occuring at ~1 atmosphere so I'm not sure how the water would behave had the external pressure been removed first. We add in cryoprotectants to prevent ice formation during these quick freeze experiments (i.e. glycerol) and this stops ice formation, yielding a smooth, glassy, tiny ball of frozen solution.

Boiling is the transition point from liquid to gas. At extremely low pressures, water would boil more easily. I'm not sure the exact outcome nor whether this type of experiment (shooting a stream into ~100K temps in a near-vaccuum) would even be possible. It'd be neat to see, though, in either case. :cool:

From Aquarius (July 2):
That's the thing. Water expands to form ice only if it is given enough time to form the ice lattice. If it can be chilled quickly enough, it'll form a glass state (i.e. no ice crystals formed), thus have no expansion.


Glassy denotes a specific solid state. There are several forms of solid water, some of them noncrystalline, some of them denser than liquid water. In any case though, it's still solid water. In other words, ice.

In a vacuum, the only type of ice formed is that which IS less dense than water. In fact, it's very near the same density as ice put in drinks.

I actually do a lot fo freezing of liquids in liquid nitrogen and vapour nitrogen streams and hit them with X-rays to check for the presence of ice. Simply plunging water into liquid nitrogen (even small volumes ~10uL or so) still yields ice formation despite the quick heat transfer. Larger volumes definitely form ice.


That's what I've been trying to explain.

Thing is, all this is occuring at ~1 atmosphere so I'm not sure how the water would behave had the external pressure been removed first.


Easy. If you removed pressure first, you'd get vaporization, plain and simple. If we're simulating orbital space, pressure wouldn't be removed first. You'd lose both pressure and temperature simultaneously. It's not difficult to gauge what could happen if use a phase diagram.

We add in cryoprotectants to prevent ice formation during these quick freeze experiments (i.e. glycerol) and this stops ice formation, yielding a smooth, glassy, tiny ball of frozen solution.


Cheater! You're giving water molecules something else to bond with other than themselves. A frozen mixture of glycerol and water isn't ice. :cool:

Boiling is the transition point from liquid to gas. At extremely low pressures, water would boil more easily.


I'm not sure what you mean by "extremely low pressures". But yes, more specifically, liquid water boils at a lower temperature as pressure is lowered. At just beyond a couple of orders of magnitude below atmospheric pressure, liquid water itself ceases to exist. It's all sublimation/deposition passed that, no boiling.

I'm not sure the exact outcome nor whether this type of experiment (shooting a stream into ~100K temps in a near-vaccuum) would even be possible. It'd be neat to see, though, in either case. :cool:


If you know someone who'd allow you to shoot a super soaker into a piece of equipment capable of such a feat, you're lucky! Also, I'm not sure where you got the 100K figure from, but I've always been talking in terms of near absolute zero.

From iSoaker.com (July 2):
In a vacuum, the only type of ice formed is that which IS less dense than water. In fact, it's very near the same density as ice put in drinks.

Where did you find out that information? For ice to be less dense than water, it'd need to be forming crystals, not freezing instantaneously into the glassy state. Sudden freeze would be, for all intents and purposes, equal to that of water since molecules would be fixed in their positions. No motion of molecules when freezing; no change in density.

If we're simulating orbital space, pressure wouldn't be removed first. You'd lose both pressure and temperature simultaneously.

That's where I'm disagreeing. While externally, both are lost, due to water's heat capacity,it'd take longer than an ideal liquid to freeze. Also, as there is no material which water would be contacting when entering a near vaccuum, the time for its heat loss would be longer, potentially allowing it to first vaporize (at least into smaller droplets) prior to the actual freezing event. I agree if the stream froze first, you'd be firing rods of ice, but I'm just not sure that would be the case due to the huge drop in pressure as well.


Also, I'm not sure where you got the 100K figure from, but I've always been talking in terms of near absolute zero.

100K is from my talk regarding liquid nitrogen. As for atmospheric temperatures, I stand surprised from info on this page by Nasa. Seems like it can be actually rather hot in orbit.

As for space temperatures, this page seems to bring more things into perspective.

As noted, vaccuums have no real temperature. Thus, this makes me question whether the liquid water stream will lose enough heat to freeze first or will it just vaporize due to lack of pressure, losing enough heat to freeze only after the vaporization event.

This is just really off this thread's topic and perhaps I'll move these posts into another thread to prevent this one from being so badly hijacked. :goofy:

:cool:

From Aquarius (July 2):
This is just really off this thread's topic and perhaps I'll move these posts into another thread to prevent this one from being so badly hijacked. :goofy:


Good idea. But maybe a moot point now.

As I suspected:

"The most similar situation I can find involves the Space Shuttle. During flight, the excess water is expelled into space. It freezes. Therefore, it is most likely that any water in a balloon in the situation you describe would freeze solid before boiling."--David Ellis, Researcher, NASA Lewis Research Center

This is taken from:

http://www.madsci.org/posts/archives/ma ... .Ph.r.html
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Post by isoaker » Sat Jul 02, 2005 5:55 pm

That info intrigued me, thus I tried digging up more info.

"The waste water vent, which is under the shuttle cabin, in front of the left wing, is used to expel into space both urine and surplus water generated from the shuttle's fuel cell power system.

Usually the water shoots out into the cold vacuum of space as a spray of crystals, but on at least one shuttle mission, in 1984, the water formed a basketball-sized chunk of ice on the lip of the vent. At the time, NASA engineers were so concerned the ice could damage the shuttle wing during re-entry that they ordered the astronauts aboard Discovery to use the shuttle's robot arm to break off the ice ball. "
From http://www.space.com/missionlaunches/st ... 30209.html

Also,
"It depends on your starting conditions of water:

Quick answer:
There are hundreds of sites on the Internet that have comprehensive
thermodynamic data on water. What you are looking for is a P-V-T
(pressure - volume - temperature) diagram. This 3 dimensional graph will
show you the state of water at a given T or P.

Here is a purely academic answer. Say for example somehow a certain volume
of liquid water @ T = 77 �F and @ P = 1 atm were to be magically placed into
space where T ~ 4 Kelvins and P = vacuum. The liquid all of the sudden will
have no pressure surrounding it. With the sudden lack of pressure the
volume of water would explosively boil off into water droplets. Shortly
thereafter, the water droplets will freeze. Why would not the block of water
just instantly freeze? In space, matter does not cool or heat the same as it
does on the ground. The ability of space to transfer heat is limited.
There is no CONDUCTIVE, or CONVECTIVE heat transfer (since these first two
methods require physical contact w/ the cooler matter)...there is only
RADIATIVE heat transfer."
From http://www.newton.dep.anl.gov/askasci/g ... n01060.htm

Finally,
"Would a glass of water in space freeze or boil?
...
Finally, we have the question of liquids in space. In a vacuum most liquids have such a low boiling point that they vaporize almost instantly. For that reason, most substances exist in space in either the gaseous or the solid state. When the astronauts take a leak while on a mission and expel the result into space, it boils violently. The vapor then passes immediately into the solid state (a process known as desublimation), and you end up with a cloud of very fine crystals of frozen urine. Ooh, ick, the sixth graders may say, but I'm betting it's one physics demonstration they wouldn't soon forget."
From
http://www.straightdope.com/classics/a1_127.html

Water in a balloon would freeze as it would be pressurized by its container. However, it appears your shuttle example actually seems to show that streams would vaporize prior to freezing as small ice crystals. As for the thought of astronaut urine in space, I always knew there were good reasons I don't like being rained upon. :goofy:

:cool:
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Post by Aquarius » Sat Jul 02, 2005 7:16 pm

Geez. This really interests you, doesn't it?
Water in a balloon would freeze as it would be pressurized by its container.


That is the hypothesis.

However, it appears your shuttle example actually seems to show that streams would vaporize prior to freezing as small ice crystals.


Ellis clearly indicates that excess water freezes without boiling. This being the case, containment in a balloon would matter little. Urine apparently is a different matter, as evidenced by your sources.




Edited By Aquarius on 1120349932

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Post by isoaker » Sat Jul 02, 2005 8:09 pm

It is interesting since I really like water and love knowing how it behaves. I'm exploring this not to prove or disprove, rather to understand things.

However, after reading, I'm still currently more believing that water would vaporize before freezing if suddenly pushed into the vaccuum of space.

As you seem to believe otherwise, that's fine, too. I'd like to test it, but am not sure how to. :goofy:

:cool:
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Post by Aquarius » Sat Jul 02, 2005 10:53 pm

It is interesting since I really like water and love knowing how it behaves. I'm exploring this not to prove or disprove, rather to understand things.


Same here. I'm just trying to help you understand.

However, after reading, I'm still currently more believing that water would vaporize before freezing if suddenly pushed into the vaccuum of space.


As I stated previously in this discussion, it is possible given the appropriate conditions, i.e. water heated beyond the boiling point at high pressure or supercritical water. Neither of these are scenarios with a soaker obviously.

As you seem to believe otherwise, that's fine, too. I'd like to test it, but am not sure how to. :goofy:


Why would Ellis lie? Given what I know of thermodynamics, I'm willing to accept his claim at face value. :bm2700:




Edited By Aquarius on 1120362828

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Post by isoaker » Sun Jul 03, 2005 6:57 am

Ellis is not lying. He's discussing water in a balloon, not free-floating in space. As he states in his reply, "The introduction of a container, even a thin balloon implies that any gas generated will be contained. Therefore, the water would no longer be in a vacuum. The equilibrium phase(s) for water at a given temperature will therefore shift as the pressure changes. " His statement regarding water freezing when ejected from the shuttle, I believe, is more to address the approximate ambient temperature, but not the behaviour of the water in a vacuum. With respect to water in a vacuum, he states, "The pressure will also affect the phase of the water. The triple point of water where liquid, gas and solid can all be present can be raised to room temperature if the pressure is decreased. This can be easily demonstrated by placing triple distilled water in a bell jar chamber and pulling a vacuum with a mechanical pump. At some point, the liquid water will be observed to simultaneously boil and freeze. "

Thing is, we're still talking about a change in temperatures and pressures from 4C (~277K) and 1 atm to basically 0 atm with no measurable temperature (vacuums cannot have a temperature as there is nothing to measure unless you're including the universal background radiation some peg at ~ 3K worth of thermal energy).

From my understanding of thermodynamics, you need a heat sink to take the energy from a substance away for it to freeze. In a vacuum, there is no where for the heat in the water to be transferred to. As such, the sudden drop in pressure would more than like blow free-floating water apart long before the water molecules have a chance to release their heat energy enough to freeze.

In a typical freezer (around -20C), one can take a water dropper and dribber out water through the -20C air. The water will remain liquid through its short fall. However, upon contact with something like metal at -20C, there's much better heat transfer, thus water hitting the metal will freeze almost instantaneously upon contact. The air and metal were both at -20C, but as metal can transfer heat much faster than air, it leads to much faster freezing of water. However, in a vacuum, there is nothing to transfer heat to.

What I'd like to know is that if water would just freeze in the void of space, where is the heat energy going to allow freezing?

If the heat energy is merely radiating from the water stream, I feel this process is too slow compared to the desire for the water to vaporize in the vacuum in order to maximize its surface area, thus allowing it to radiate off latent heat energy more quickly. From my understanding, the water should still vaporize prior to the freezing event. Water does not radiate off thermal energy as efficiently as a black-body would, thus as the system strove to reach equilibrium, I foresee a volume expansion (vaporization) first prior to the temperature drop.

:flashflood::cool:
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Post by Aquarius » Sun Jul 03, 2005 12:09 pm

Well, I'm not going to hypothesize the what's and how's ad nauseam. We've got (supposedly) a NASA researcher clearly stating regarding the space shuttle:

"During flight, the excess water is expelled into space. It freezes."--Ellis

No boiling, no balloons. It freezes, period.

What we don't know are the conditions at which shuttle liquids are kept prior to ejection nor specific information on ejection itself (port configuration, flow, etc.). If we had this, we could compare it to a soaker and we'd be in much better shape.

Given your interest in water, I strongly recommend you get a phase diagram for it, a really good one at that. You will see that there could be instances where, in the context of our discussion, water would freeze instantly, where it would boil off, or anything else in between, in any order, on its way to becoming solid.

Here's a pretty good one:

http://www.lsbu.ac.uk/water/phase.html




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Post by isoaker » Sun Jul 03, 2005 1:15 pm

Given your interest in water, I strongly recommend you get a phase diagram for it, a really good one at that. You will see that there could be instances where, in the context of our discussion, water would freeze instantly, where it would boil off, or anything else in between, in any order, on its way to becoming solid.


Phase diagrams represent systems at equilibrium. However, what we're discussing is a changing system, not one at equilibrium. I am well versed and knowledgable when it comes to phase diagrams. Pointing to a phase diagram does not account for the status of a given material as it goes through its transitions. Water, at -20C at 1atm, is frozen. However, whether it freezes in a big chunk or in little droplets depends on how it got to that end point. If you fill a glass of water and place it at -20C and wait for the heat to escape, you'll have a nice chunk of ice. However, if you boiled the water first, then condensed the vapour on a sheet of metal, then froze it at -20C, you'd have lots of little tiny ice crystals, but not one big chunk. In both cases, the water is frozen happily at -20C, but its shape (one chunk versus lots of little crystals) is rather different though the overall volume, mass, and temperature would remain equal.

As well, taking a subset of an answer as the explanation to the entire answer is dangerous, especially when the question was formulated for a specific system as Ellis first disregarded the possibility of the water in a vacuum by stating that "any gas generated will be contained". This nullifies vacuum experienced by the water in his answer, thus leaving only the temperature factor remaining. The 'balloon' in the question is assumed to be a "membrane [that] is impermeable and well prettyt tough".

I agree once the water solidifies, it'll be solid even as pressure drops. However, the intial conditions still allow the possibility of different routes towards the end-point to be taken.

Water being ejected into space freezes, but from what I've read in other articles, it freezes as a fine mist/shower of ice particles, not as a stream or as solid droplets.

You will see that there could be instances where, in the context of our discussion, water would freeze instantly

Water cannot freeze instantly unless you can suddenly extract all its heat energy.

The heat from liquid water must go somewhere before the water can freeze. In a vacuum, I cannot account for where the heat would go quickly enough to allow for freezing prior to the water vaporizing for being at sub-optimal pressures to allow for liquid condensation. For this answer, phase diagrams alone are not enough to account for what would happen to a stream in space. What is needed is the path along the phase diagram from starting to end-point to understand what would happen to the stream. (As an aside, that's a pretty cool phase diagram you provided a link to. There's a lot of info there on water and ice I hadn't known before. :cool:)

Edit: just found this on the MadSci Network:

Date: Mon May 4 09:30:44 1998
Posted By: John Haberman, Space Scientist, NASA Goddard Space Center, Greenbelt MD
Area of science: Astronomy
ID: 893798162.As
--------------------------------------------------------------------------------
Message:


John,

Water has been observed both in outer space and on several planets and
moons. Earth is the only place, so far, where water is known to exist in
the liquid phase. Water vapor has been found essentially everywhere. It
is believed (or hypothesized) that solid water (ice) exists on some
planets and moons. Much speculation and debate is currently occurring as
to how much water is really present on some of the planets or moons.

I believe that your question really is -- If liquid water is suddenly
put into outer space, will it boil or freeze? The most correct answer is:
Both! If you check the scientific definitions of freezing and of boiling
you will find that what occurs can be interpreted as both. The
observations of the water released from the space shuttle show that it
both evaporates and freezes and that the resulting ice then quickly
sublimates (converts directly from the solid to the gas phase).

From http://www.madsci.org/posts/archives/ma ... .As.r.html

Based on that, I somehow don't foresee a stream surviving intact or even as long icy shards.

:cool:
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Post by Aquarius » Sun Jul 03, 2005 5:59 pm

isoaker_com wrote:Phase diagrams represent systems at equilibrium. However, what we're discussing is a changing system, not one at equilibrium.

Yes indeed.

I am well versed and knowledgable when it comes to phase diagrams. Pointing to a phase diagram does not account for the status of a given material as it goes through its transitions.


Not it does not, but one is able to rationalize possibilities from information on the diagram.

I agree once the water solidifies, it'll be solid even as pressure drops. However, the intial conditions still allow the possibility of different routes towards the end-point to be taken.


Exactly--possibilities that include freezing first. This what I've been trying to say.

Water being ejected into space freezes, but from what I've read in other articles, it freezes as a fine mist/shower of ice particles, not as a stream or as solid droplets.


I realize that both can and do occur, but have read nothing to the effect of initial conditions under which either did. A "fine mist/shower of ice particles" is vague. What's the difference in size between a "particle" and a "droplet"? Also, it is possible to expel water AS a "fine mist", having it freeze as such (does a "mist" vaporize?). Yet again, what are the conditions? So many questions, so may possibilites.

Water cannot freeze instantly unless you can suddenly extract all its heat energy.


In this context, "instantly" or "suddenly" simply implies "before vaporization". Furthermore, water needn't lose ALL latent heat to revert to solid. Heat of fusion plus that keeping it in liquid form is sufficient.

The heat from liquid water must go somewhere before the water can freeze. In a vacuum, I cannot account for where the heat would go quickly enough to allow for freezing prior to the water vaporizing for being at sub-optimal pressures to allow for liquid condensation.


I truly hope at this point you realize that it can happen, whether or not you know how. Some cannot fathom how a volume of water at 10 C can freeze SLOWER than an equal volume that is several degrees warmer, but it's possible. Sometimes intuition and physics don't seem to agree.

For this answer, phase diagrams alone are not enough to account for what would happen to a stream in space. What is needed is the path along the phase diagram from starting to end-point to understand what would happen to the stream.


A path indeed--one of which we have no idea without a starting point. Would you not agree that, if simply opened to outer space, water at 4 C and 1 atm is far less likely to vaporize than that at the same temperature but at 9.87e-03 atm? What about comparison of a -4 C ice cube at the same initial pressures? Surely one would expect more immediate sublimation from the one at low initial pressure.

(As an aside, that's a pretty cool phase diagram you provided a link to. There's a lot of info there on water and ice I hadn't known before.


I'm glad you like it.

Edit: just found this on the MadSci Network:
Date: Mon May 4 09:30:44 1998
Posted By: John Haberman, Space Scientist, NASA Goddard Space Center, Greenbelt MD
Area of science: Astronomy
ID: 893798162.As
--------------------------------------------------------------------------------
Message:


John,

Water has been observed both in outer space and on several planets and
moons. Earth is the only place, so far, where water is known to exist in
the liquid phase. Water vapor has been found essentially everywhere. It
is believed (or hypothesized) that solid water (ice) exists on some
planets and moons. Much speculation and debate is currently occurring as
to how much water is really present on some of the planets or moons.

I believe that your question really is -- If liquid water is suddenly
put into outer space, will it boil or freeze? The most correct answer is:
Both! If you check the scientific definitions of freezing and of boiling
you will find that what occurs can be interpreted as both. The
observations of the water released from the space shuttle show that it
both evaporates and freezes and that the resulting ice then quickly
sublimates (converts directly from the solid to the gas phase).


Based on that, I somehow don't foresee a stream surviving intact or even as long icy shards.


Technically, it won't survive indefinately as ice in any form, no matter what happens immediately after exposure. How quickly it sublimes depends on the volume and surface area, but it will ultimately sublime, as Haberman indicates.




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Post by isoaker » Sun Jul 03, 2005 6:57 pm

As I said earlier, I'm just fleshing out thoughts and am glad by the discussion thusfar.
In this context, "instantly" or "suddenly" simply implies "before vaporization". Furthermore, water needn't lose ALL latent heat to revert to solid. Heat of fusion plus that keeping it in liquid form is sufficient.


The thing here is how much latent heat must be lost to allow for the solidification of ice from liquid. For sake of argument, I'm sticking with the assumption that we're dealing with water initially at 4C, 1atm. To strip water and make it freeze, you need to remove ~6.02 kJ/mol .

The heat from liquid water must go somewhere before the water can freeze. In a vacuum, I cannot account for where the heat would go quickly enough to allow for freezing prior to the water vaporizing for being at sub-optimal pressures to allow for liquid condensation.



I truly hope at this point you realize that it can happen, whether or not you know how. Some cannot fathom how a volume of water at 10 C can freeze SLOWER than an equal volume that is several degrees warmer, but it's possible. Sometimes intuition and physics don't seem to agree.

I can appreciate it may happen under given conditions, but I'd like to know what those conditions are. On the phase diagram, from the starting point of 4C and ~101.325mPa, I still feel it's more probable for the water to experience the drop in pressure first, pushing it into the vapor phase, prior to experiencing the drop in temperature. This is further compounded by water's heat of fusion as it must lost that extra amount of energy for it to go from a liquid to a solid.

Of course, theory and reality can differ. Now if only there were a way to get an astronaut to bring along a soaker (well, a modified one capable of withstanding space exposure) and fire off a couple of shots. :goofy:

:cool:
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Aquarius
Posts: 70
Joined: Sun Jul 04, 2004 11:55 pm
Location: Mississippi, USA

Post by Aquarius » Sun Jul 03, 2005 9:04 pm

isoaker_com wrote:The thing here is how much latent heat must be lost to allow for the solidification of ice from liquid. For sake of argument, I'm sticking with the assumption that we're dealing with water initially at 4C, 1atm. To strip water and make it freeze, you need to remove ~6.02 kJ/mol .
Don't forget the energy sustaining the water at 4 C. It's got to go too.
Of course, theory and reality can differ. Now if only there were a way to get an astronaut to bring along a soaker (well, a modified one capable of withstanding space exposure) and fire off a couple of shots. :goofy:


This is just what I heard, but science experiments may be conducted on the shuttle for around $3,000. I'd imagine spacewalking would cost extra.
:goofy:

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