# vacuum in space
**URL:** https://boards.straightdope.com/t/vacuum-in-space/63741
**Category:** Factual Questions
**Created:** [April 29, 2001, 5:16pm UTC](https://boards.straightdope.com/t/vacuum-in-space/63741 "2001-04-29T17:16:41Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@kmudd20001](https://boards.straightdope.com/u/kmudd20001)
#### Post date: [April 29, 2001, 5:16pm UTC](https://boards.straightdope.com/t/vacuum-in-space/63741/1 "2001-04-29T17:16:41Z")
If a vacuum in a thermos bottle insulates the inside of the bottle ,why doesn’t the vacuum of space insulate spaceships?
Shouldn’t the heat generated inside by the electronics cause it to overheat?
Apollo 13 froze when the power was turned off. Why didn’t the sun keep it warm?
It is the small amount of matter flowing past or the evaporation of gases from the ship the cools it off?
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### Author:  [@Doc\_Nickel](https://boards.straightdope.com/u/Doc_Nickel)
#### Post date: [April 29, 2001, 6:45pm UTC](https://boards.straightdope.com/t/vacuum-in-space/63741/2 "2001-04-29T18:45:47Z")
This has been explained at length in some of the recent “Moon Hoax” sites and threads…
Long story short, the vacuum insulates from direct heat conduction- IE, through the air, through the metal or plastic of the thermos itself, etc.
BUT, it doesn’t prevent heat loss via radiation (infrared.)
Ever feel the heat of the sun through a double-pane insulated window? That’s infrared.
A warm object in space WILL lose heat via infrared radiation. It doesn’t lose heat as fast as it would were a cool breeze of nice, dense air were blowing on it, but it DOES lose it nonetheless.
Electronics and other power-consuming devices do generate heat, but typically not enough to overheat a ship or station in space.
The sun didn’t keep Apollo 13 warm because the craft was designed NOT to absorb excess solar heat. It’s easier to use a little electrical power to generate a little more heat, than it is to easily shed a little excess heat while in space.
The space suits the astronauts wore on the moon used small quantites of water sprayed on cooling coils to help shed heat. The water froze on the coils then sublimated off into space, taking the excess heat with it.
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### Author:  [@kmudd20001](https://boards.straightdope.com/u/kmudd20001)
#### Post date: [April 29, 2001, 6:50pm UTC](https://boards.straightdope.com/t/vacuum-in-space/63741/3 "2001-04-29T18:50:56Z")
Thanks for the answer! I had a friend who asked me this question. He might have saw it on one of those Moon Hoax sites.
Kevin
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### Author:  [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)
#### Post date: [April 29, 2001, 7:23pm UTC](https://boards.straightdope.com/t/vacuum-in-space/63741/4 "2001-04-29T19:23:55Z")
Note also that yes, this may in fact be a problem with spacecraft, and is engineered for. See, for example, this NASA article [Space Station Radiator Test Hosted by NASA Lewis at Plum Brook Station](http://www.grc.nasa.gov/WWW/RT1997/6000/6920speth.htm).
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### Author:  [@GargoyleWB](https://boards.straightdope.com/u/GargoyleWB)
#### Post date: [April 30, 2001, 1:29am UTC](https://boards.straightdope.com/t/vacuum-in-space/63741/5 "2001-04-30T01:29:39Z")
Also, the inside vacuum portion of a thermos is silvered, so that the radiative energy of your hot coffee is reflected back into the coffee. It is this silvered surface in combination with the vacuum that makes it such a good insulator.
In college, we would frequently use liquid nitrogen (too lazy to look it up but was around -70 Celsius). I left about a pint of it on the lab table once in an _open_ insulating flask, when I came back the next day only half of it had boiled away (in this case the flask is silvered to reflect heat from the outside).