Behavior of water in a vacuum?

[Ender55]

I've been reading about what happens to water when exposed to vacuum, but can't seem to find a definitive answer concerning a few details in the step-by-step process. I read that water will quickly boil in the vacuum of space due to very low pressure, and then freeze. But roughly how long does it take to freeze? Say a glob of temperate water with the volume of about a shot glass is suddenly exposed to the vacuum of space. Would the whole thing quickly boil away into gas, and then the vapor desublimates? Or would any portion of the water transform directly from liquid to solid? For desublimation in these circumstances, and if at all roughly possible to calculate, how big/thick would the resulting ice crystal cloud be? How long would this entire process take? A moment? Or full seconds or minutes? Would the cloud look like snow? Would you be able to mush it into an ice/snow ball?

 

[Bobbywhy]

Ender55, Welcome to Physics Forums!

Urine and wastewater are often jettisoned from manned satellites into space. Waste water usually freezes upon jettison into a cloud of tiny ice droplets. Then when the sun hits, the ice sublimates directly into water vapor and disperses in space.

http://www.space.com/7274-mystery-explained-glow-night-sky-astronaut-urine.html

 

[Lsos]

Interesting...I thought they try to recycle every last gram of water in space. They just dump it out? Doesn't seem very sophisticated.

 

[Dadface]

Tut tut.All these astronauts are turning the space around our Earth into a giant sewer.It reminds me of the days when people used to empty their pots into the street

 

[Bobbywhy]

One can google "satellite waste water urine" and find great photos illumintated by the sun of frozen water/urine plumes trailing out from objects in space. One more small step for mankind, who seems destined to pollute every place he visits, including space.

 

[A.T.]

Urine and wastewater are often jettisoned from manned satellites into space.

What about the more solid stuff? Is it taken back to Earth? Is it released such that it burns in the atmosphere soon? Or will we read about a satellite destroyed by frozen poo one day?

 

[sophiecentaur]

Water, in a small evacuated container, will evaporate until the pressure in the container is equal to the vapour pressure of the liquid at its temperature. This is no different with or without the presence of air in the container. (The law of partial pressures applies everywhere)
It has been written many times before on PF: Air is not a sponge - it does not absorb water - it just looks that way.

If the container is large enough (space) the the pressure will always be lower than the vapour pressure so the water will all evaporate. For a very large mass including water (an orbiting comet, for instance), the gravitational self-attraction will hold the vapour near the core and, if the temperature drops, it will re-condense, only to boil off the next time it goes close to the Sun.

 

[Bobbywhy]

Mr. SC above accurately described icy comet behaviours. This below describes man-made water/urine dumps in space:

“Waste water usually freezes upon jettison into a cloud of tiny ice droplets. Then when the sun hits, the ice sublimates directly into water vapor and disperses in space.”

http://www.space.com/7274-mystery-explained-glow-night-sky-astronaut-urine.html

Furthermore, there was a report of a satellite being damaged by frozen poo, I just can't seem to find it now...

 

[dennys87]

how can you remove the water vapor from the vacuum chamber to keep the evaporation process continuing?

 

[sophiecentaur]

Keep pumping!