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Solved: hypothetical question

Discussion in 'Hardware' started by valis, Jan 27, 2006.

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  1. valis

    valis Moderator Thread Starter

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    VERY hypothetical.

    Got a mechanical engineer friend of mine, pretty astute sort of fellow. We got into a discussion yesterday about computers in space. Don't ask why, common problem we have. His stance is that pc's in space need more cooling fans as they have a tendency to overheat. My view is that they will need no more than the average computer, as it is forced convection, not standard convection.

    Also, I think that due to a lack of gravity, the fans in question would last longer, as there isn't the gravitational stress on the ball bearings. Now, I know that one is not taking a windows based pc up in orbit, and that they are all pretty much custom designed OS's, but I still don't think that there would be any more pull on the processor than an earth-bound pc, possibly even less.

    Ideas?
     
  2. buddhafabio

    buddhafabio

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    it depends on the relation of the computer to the sun. the side that faces it gets real hot where as the side away is cold.

    thus if a satalite is in the dark side of the earth in stationary orbit it goes through stresses unheard of. also the electronics on the planet are protected from the suns solar flares by our megnetosphere but computers in space dont have that luxury.

    and i heard recently that some people are testing if computers can be made off the shelf and go in to space.
     
  3. StumpedTechy

    StumpedTechy

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    Actually here is a good read.. its all relational as to how far from the planet/sun the electronics are.

    http://spider.ipac.caltech.edu/staff/waw/mad/mad5.html

    http://www.newton.dep.anl.gov/askasci/ast99/ast99383.htm

    I.E. its saying if your close to a body that is being heated that you will get the radient energy of the planet to heat things up. but the further away it is from that heat source the less warm it will be.

    So really if your making an all purpose PC for space travel your going to have to design it to work in all types of conditions.
     
  4. JosephByers

    JosephByers

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    A lot depends on the vehicle in which the computer is contained. If this is a closed environment which is air conditioned, then there should be no problem with temperature control. If this is an open environment, then it depends on many other factors. One factor is whether it is in direct sunlight or not. If the computer is insulated from heat conductive material and in the shade of a reflector and also insulated from radiant heat from that reflector, then it would be very cold. That leads to the possibility of using super-conductors. Of course being in direct sunlight can fry wiring and melt solder if it is intense enough.
    On the other hand, NASA has been using onboard computer in their spacecraft for quite a while. I suspect that it isn't much of a problem.
     
  5. D0C_Hol1d@y

    [email protected]

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    LOL this is great. Your freind would be correct if the computer was outside of a atmosphere in space. Space has no air at all. The fans would do nothing. Inside a space ship it would work normal. I think that with all the technology some liquid cooled machines would be in order.
     
  6. valis

    valis Moderator Thread Starter

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    okay, let's take away all external heat related issues, such as the sun warming and all that. Base question is whether or not a forced convection pc, such as we are sitting in front of now, would overheat in space. He says yes; I say no, and I'm sort of digging my heels in on this one.

    Joseph: The scenario in question is on the ISS, so it would be air conditioned for humans to probably circa 70 F. So the ambient temperature is pretty cool. It would be in a place that the stresses of continous sunrise/set wouldn't effect it.

    Doc: I actually mentioned the liquid cooling yesterday during our discussion, good point. He is convinced that the lack of gravity would ruin the forced convection premise, as the hot air woudn't rise, as there is no 'up' for the less dense to to migrate to. I feel that the pockets of hot air that would remain would be, by definition of forced convection, away from critical areas.

    But I think you guys are agreeing with me on this one.

    v
     
  7. JohnWill

    JohnWill Retired Moderator

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    You would still need forced air, since the weightless environment would not cause hot air to rise as it does here on the earth. I'm sure not that much movement would be required, but you need something to convince the hot air to move. :)
     
  8. valis

    valis Moderator Thread Starter

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    cool, no pun intended. That's what I thought. Thanks for all the input.

    v
     
  9. gotrootdude

    gotrootdude

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    Actually, you would not use air convection as all. The dissapation of heat is of upmost importance in the design of any space vehicle, so important that the first thing the space shuttle does in space is open the bay door so that special infrared radiators can be used to rid the shuttle of excess heat. The same raditors-thermos, along with gas liquid phased heat tubes and simple heat exchangers would be used. Therefore the excess heat would be converted to infrared and allowed to radiate away.
     
  10. gotrootdude

    gotrootdude

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  11. valis

    valis Moderator Thread Starter

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    good article, but I think you bypassed the point. I understand the importance of heat dissipation as it pertains to any orbiting vehicle, be it manned or otherwise. But what I am talking about here is the actual pc itself, in a vehicle that has humans on-board, so the internal ambient temperature would be circa 70 F. The question posed was whether or not forced convection would work in cooling down the pc, as in space, the excited hot molecules would not 'rise' per se, as there is no 'up'.

    This all started when I was talking to him and found out that he had done some work on one of pc's on the ISS; as I mentioned, fairly astute lad. He mentioned that it had 24 fans, which I found a bit excessive, and mentioned it to him. He said that it was necessary 'due to the lack of gravity'. I called shenanigans, and we discussed it for a bit. After sleeping on it, I was more certain I was right, that a standard pc would not need any extra fans, and in fact, the extra fans could actually obstruct the designed flow of air.

    In further discussions, after I closed this post, it turned out that that tower was so crammed with stuff (6 scsi bays, all occupied, 2 sata drives, etc etc ad infinatum) that the 24 fans were all mini-fans placed to blow across critical components to move the heat into the river of air that the forced convection fans had created.

    v
     
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