verbal_jizm: Heat is molecular kinetic energy, Dumbmitter. Not much to transfer that to in a near vacuum.
Old Man Winter: GAH THE HEAT HAS NO WHERE TO GO. SCIENCE FOOL!
Jim_Callahan: Old Man Winter: GAH THE HEAT HAS NO WHERE TO GO. SCIENCE FOOL!Heat transfer has a radiation term, actually, convection dominates under most conditions in the region of temperature and pressure we live in, but for very high temperatures and low pressures radiation can be a significant or even dominant factor.But yes, since optical instruments tend to run at room temperature or lower (and radiation scales with T^4) you're going to have to rely mostly on some form of evaporation-based cooling out in space where there's no ambient convection or conduction. A system capable of cooling based on EM emission alone would need a farkton of surface area, which would backfire if your device ever saw the sun.
Seamer: Isn't helium one of the most abundant elements out there?
Honest Bender: verbal_jizm: Heat is molecular kinetic energy, Dumbmitter. Not much to transfer that to in a near vacuum.Why does it get cold at night, but hot during the day?
Peki: *grabs popcorn and waits for the "HEAT DOES NOT WORK THAT WAY" fight*
ZAZ: Helium is the third most abundant element in the universe, after hydrogen and stupidity.
Raoul Eaton: It's just really hard to mine it from the core of a star. Helium, I mean, not stupidity.I believe that on Earth the main source of it is in Texas.
Honest Bender: Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.
Raoul Eaton: Peki: *grabs popcorn and waits for the "HEAT DOES NOT WORK THAT WAY" fight*It's already on. Not much of a fight though.
scott4long: [imageshack.us image 480x360]
Ivo Shandor: Honest Bender: Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.Exposing it to space would actually provide unwanted heating, not cooling.The temperature of deep space (cosmic microwave background radiation) is about 2.7K. The boiling helium on this spacecraft cooled the instruments to 1.7K, and additional cooling systems took some detectors down to 0.3K (section 18.104.22.168).
rubi_con_man: Honest Bender: Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.This -What they are effectively doing is taking the incident energy - the heat that the telescope is exposed to as well as the heat of the components running, and trying to transport it away to a 'safe' location from which they can get rid of the energy by focusing the heat onto a component which will "shine" and release the energy as light.
FrancoFile: ... I guess we should cut him a little slack./who am I kidding//nah
cretinbob: FrancoFile: ... I guess we should cut him a little slack./who am I kidding//nahHell no. Submitter clearly lacks even a 6th grade education.
kayanlau: I'm reading all your angry comments out loud in a high-pitched, helium filled voice.
kryptin420: Seamer: Isn't helium one of the most abundant elements out there?Sure, if you can get at it. Our reserves on this planet are actually running out as helium just flies off the planet if released in the atmosphere. Current estimates say we could be in trouble of running out around 2030. If we want more we are going to need to goto the moon or another planetary body.
Brontes: Not to piss on everyone pissing on submitter, but:Abstract:The basic principles of radiative cooling of electronic components and subassemblies in a satellite are discussed, and estimates are made of the lowest temperatures attainable in a satellite by completely passive means. It appears feasible to maintain some compartments within a satellite at temperatures of 250Â°K or lower, so an opportunity is presented for refrigerating components whose characteristics are enhanced at lower temperatures. And:http://www.tak2000.com/data/Satellite_TC.pdf (page 50 and onward discuss passive cooling)Heat pipes....in space!!
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