liquids in space

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wert_fleming

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<p>&nbsp;</p><p>I have a simple question. Are ther any known substance's that will keep their liquid state in the cold of space. I would like to submit an experiment to nasa for the space station.</p>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;I have a simple question. Are ther any known substance's that will keep their liquid state in the cold of space. I would like to submit an experiment to nasa for the space station. <br />Posted by wert_fleming</DIV></p><p>Do you mean in the vacuum of space as well ?<br /></p> <div class="Discussion_UserSignature"> </div>
 
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wert_fleming

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Do you mean in the vacuum of space as well ? <br />Posted by DrRocket</DIV></p><p>&nbsp;yes, if the physical state is changed in a vacuum. I understand that liquiids have different natures under various pressures. What I would like to do is put a given amount of a liquid into space in the path of a instrument package that would measure the changes in velocity and inertia upon impact to see if it would be useful in changing the trajectory of an object. If a liquid can not be found then possibly a solar mirror or laser system to project heat on the substance to keep it close to a liquid state. Would this be feasible?</p>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;yes, if the physical state is changed in a vacuum. I understand that liquiids have different natures under various pressures. What I would like to do is put a given amount of a liquid into space in the path of a instrument package that would measure the changes in velocity and inertia upon impact to see if it would be useful in changing the trajectory of an object. If a liquid can not be found then possibly a solar mirror or laser system to project heat on the substance to keep it close to a liquid state. Would this be feasible? <br />Posted by wert_fleming</DIV></p><p>One property of liquids is vapor pressure.&nbsp; It varies with temperature.&nbsp; When the vapor pressure exceeds the ambient pressure the liquid boils, meaning it turns into a gas.&nbsp; The ambient pressure in space is essentially zero.&nbsp; Liquids will tend to gassify very quickly.&nbsp; Your problem is going to be more one of preventing the liquid from quickly evaporating than from keeping it from freezing.</p><p>Vacuum chambers on earth are often used to dry things.&nbsp; The vacuum in these chambers is not so nearly perfect as is space.&nbsp; Before you try your experiment in space, you ought to see what happens in a vacuum chamber.</p><p>Space is not really cold in the sense that you mean.&nbsp; The background temperature, for purposes of radiative heat transfer is low -- 2.73 K.&nbsp; But surfaces exposed to direct sunlight can become quite hot.&nbsp; So space is really a matter of contrasts.&nbsp; Things in the shade will cool off fairly quickly to low temperatures.&nbsp; But things in the sunlight will become quite hot.&nbsp; And things exposed to radiation from the earth will be in between.&nbsp; There will be no loss or gain of heat by conduction, only loss or gain by radiatioin.</p><p>The effect that you are trying to determine could probably be calculated using a reasonably sophisticated computer code.&nbsp;&nbsp; You don't need an expensive space experiment. &nbsp;But why would you want to use a liquid ?&nbsp; The effect will be to a large extent a function of the specific point of impact of the incoming body on the blob of liquid, if is remains a blob, and if it remains a liquid.&nbsp; It may well disperse as it heats since not much except surface tension will be holding it together.&nbsp;And once it breaks up into little blobs with more surface area, the quicker it will evaporate, or freeze.&nbsp;Then what happens is anybody's guess since you won't know the effective mass involved, or the geometry of the collisions of the incoming body with the various bits a pieces of the liquid/solid/gas.</p><p>If you use a solid the effect is easily calculated -- basically a 3-dimensional game of billiards.</p><p>If what you are thinking about is a scheme to deflect an incoming asteroid to avoid a potential collision with earth, I can predict the outcome of your experiment.&nbsp; First, unless you have a huge mass of liquid, and are really far away from earth the deflection of an asteroid would be very small, unless the asteroid itself is so small that you really don't care anyway.&nbsp; Second the collision will tend to be relatively inelastic since there are plenty of mechanisms for dissipation of energy, so the mechanism will not be as effective in diverting the asteroid as would an elastic collision with a solid body.&nbsp; Third, the mass of liquid that you would&nbsp;have to transport to make a big change would be prohibitive given the availablity propulsion capability.</p><p>It is a game of momentum and there are more effective means to change momentum, and even those won't make a large change in the momentum of something as massive and fast-moving as an asteroid.&nbsp; The key is to make the changes sufficiently far out that only a small change is needed to avoid a collision.&nbsp; And that means being able to take action quite far away from earth, which in turn means taking action with a means that is effective but not terribly massive.&nbsp; It is a tough problem.</p><p>I am not sure what you mean by measuring changes in inertia. Inertia is just a word.&nbsp; The closest physical property is mass.&nbsp; And the mass will not change unless some of the liquid sticks to the surface of the incoming body.&nbsp; That is not likely to be much unless the incoming body has a very large surface area.&nbsp; You might also mean momentum when you say "inertia" but momentum is just mass times velocity.</p><p>So, I think the experiment that you propose might be relatively difficult to do in a meaningful way.&nbsp; This is because of the potential change of state of the liquid to a gas and only secondarily to a solid (if it is shadowed by the earth and has time to cool radiatively).&nbsp; But more importantly I think that the major purpose of your experiment is more easily and cheaply determinend by calculation, supplemented by data easily obtained in an earth-bound laboratory.&nbsp; A computer model would also allow you to change boundary conditions and check out several cases, effectively allowing many trials of the experiment under slightly different conditions.&nbsp; But you may be able to determine feasibility of your underlying idea with simple hand calculations.<br /></p> <div class="Discussion_UserSignature"> </div>
 
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wert_fleming

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<p>Thank you for the information you have given me. It is a good place to start. I have a friend that is going to help me with the calculations and I will try to return a post on what we find. thanks again.&nbsp; </p><p>[</p><p>QUOTE]One property of liquids is vapor pressure.&nbsp; It varies with temperature.&nbsp; When the vapor pressure exceeds the ambient pressure the liquid boils, meaning it turns into a gas.&nbsp; The ambient pressure in space is essentially zero.&nbsp; Liquids will tend to gassify very quickly.&nbsp; Your problem is going to be more one of preventing the liquid from quickly evaporating than from keeping it from freezing.Vacuum chambers on earth are often used to dry things.&nbsp; The vacuum in these chambers is not so nearly perfect as is space.&nbsp; Before you try your experiment in space, you ought to see what happens in a vacuum chamber.Space is not really cold in the sense that you mean.&nbsp; The background temperature, for purposes of radiative heat transfer is low -- 2.73 K.&nbsp; But surfaces exposed to direct sunlight can become quite hot.&nbsp; So space is really a matter of contrasts.&nbsp; Things in the shade will cool off fairly quickly to low temperatures.&nbsp; But things in the sunlight will become quite hot.&nbsp; And things exposed to radiation from the earth will be in between.&nbsp; There will be no loss or gain of heat by conduction, only loss or gain by radiatioin.The effect that you are trying to determine could probably be calculated using a reasonably sophisticated computer code.&nbsp;&nbsp; You don't need an expensive space experiment. &nbsp;But why would you want to use a liquid ?&nbsp; The effect will be to a large extent a function of the specific point of impact of the incoming body on the blob of liquid, if is remains a blob, and if it remains a liquid.&nbsp; It may well disperse as it heats since not much except surface tension will be holding it together.&nbsp;And once it breaks up into little blobs with more surface area, the quicker it will evaporate, or freeze.&nbsp;Then what happens is anybody's guess since you won't know the effective mass involved, or the geometry of the collisions of the incoming body with the various bits a pieces of the liquid/solid/gas.If you use a solid the effect is easily calculated -- basically a 3-dimensional game of billiards.If what you are thinking about is a scheme to deflect an incoming asteroid to avoid a potential collision with earth, I can predict the outcome of your experiment.&nbsp; First, unless you have a huge mass of liquid, and are really far away from earth the deflection of an asteroid would be very small, unless the asteroid itself is so small that you really don't care anyway.&nbsp; Second the collision will tend to be relatively inelastic since there are plenty of mechanisms for dissipation of energy, so the mechanism will not be as effective in diverting the asteroid as would an elastic collision with a solid body.&nbsp; Third, the mass of liquid that you would&nbsp;have to transport to make a big change would be prohibitive given the availablity propulsion capability.It is a game of momentum and there are more effective means to change momentum, and even those won't make a large change in the momentum of something as massive and fast-moving as an asteroid.&nbsp; The key is to make the changes sufficiently far out that only a small change is needed to avoid a collision.&nbsp; And that means being able to take action quite far away from earth, which in turn means taking action with a means that is effective but not terribly massive.&nbsp; It is a tough problem.I am not sure what you mean by measuring changes in inertia. Inertia is just a word.&nbsp; The closest physical property is mass.&nbsp; And the mass will not change unless some of the liquid sticks to the surface of the incoming body.&nbsp; That is not likely to be much unless the incoming body has a very large surface area.&nbsp; You might also mean momentum when you say "inertia" but momentum is just mass times velocity.So, I think the experiment that you propose might be relatively difficult to do in a meaningful way.&nbsp; This is because of the potential change of state of the liquid to a gas and only secondarily to a solid (if it is shadowed by the earth and has time to cool radiatively).&nbsp; But more importantly I think that the major purpose of your experiment is more easily and cheaply determinend by calculation, supplemented by data easily obtained in an earth-bound laboratory.&nbsp; A computer model would also allow you to change boundary conditions and check out several cases, effectively allowing many trials of the experiment under slightly different conditions.&nbsp; But you may be able to determine feasibility of your underlying idea with simple hand calculations. <br />Posted by DrRocket[/QUOTE]<br /></p>
 
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