UARS Satellite re-entry
Discussion
Simpo Two said:
Radiation seems to work for the sun 
And if the heat of the reactor is absorbed by the sodium, how does that then dissipate its heat? Surface area has no role (I think) as that's a convection thing.
Three methods of losing heat - conduction, convection and radiation. Only radiation works in space, so the radiators need to be a lot larger than they would be on earth. Anyway, that's why sodium cooled - sodium can get massively hotter than water while remaining liquid meaning it can remove more heat energy from the core.And if the heat of the reactor is absorbed by the sodium, how does that then dissipate its heat? Surface area has no role (I think) as that's a convection thing.
davepoth said:
Simpo Two said:
If they are orbiting in a vacuum at about absolute zero, what can cooling do?
It's surprisingly difficult to get rid of heat in a vacuum.It was absolutely essential that the Shuttle opened its cargo bay doors within about 40 to 60 minutes of reaching orbit. Inside the cargo bay doors were huge radiators. If those doors couldn't be opened for any reason, the Shuttle would start to overheat and the mission would have to be aborted.
In this picture you can see the radiator surfaces on the inner face of the cargo bay doors -
el stovey said:
BuzzLightyear said:
A little research shows that UARS (YouArse?)
That's the story here, never mind that there is a 1:3500 chance someone is going to get hit by space debris in the great re entry lottery. The best part is that someone called a satellite 'you arse'.
Last update from NASA:
"Fri, 23 Sep 2011 03:01:35 AM GMT
As of 9:30 p.m. EDT Sept. 22, 2011, the orbit of UARS was 110 mi by 115 mi (175 km by 185 km). Re-entry is possible sometime during the afternoon or early evening of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 hours."
http://www.nasa.gov/mission_pages/uars/index.html
The live tracking site is struggling with internet overload at the moment:
http://www.n2yo.com/
This all reminds me of Skylabs re-entry in '79 over Australia.
"Fri, 23 Sep 2011 03:01:35 AM GMT
As of 9:30 p.m. EDT Sept. 22, 2011, the orbit of UARS was 110 mi by 115 mi (175 km by 185 km). Re-entry is possible sometime during the afternoon or early evening of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. It is still too early to predict the time and location of re-entry with any more certainty, but predictions will become more refined in the next 24 hours."
http://www.nasa.gov/mission_pages/uars/index.html
The live tracking site is struggling with internet overload at the moment:
http://www.n2yo.com/
This all reminds me of Skylabs re-entry in '79 over Australia.
davepoth said:
Three methods of losing heat - conduction, convection and radiation. Only radiation works in space, so the radiators need to be a lot larger than they would be on earth. Anyway, that's why sodium cooled - sodium can get massively hotter than water while remaining liquid meaning it can remove more heat energy from the core.
Right, so the heat gradient between the hot sodium and cold space is greater. Gottit.What stops the heat soaking back into whatever it is that is wanting to be cooled?
anonymous said:
[redacted]
Not sure i agree with that...The chance of you winning the lottery is 1 in ~14 million.
The chance of the satellite hitting a person (i.e anybody) is 1 in 3,200. There are ~7 billion people in the world, so the chance of it hitting you specifically, based on the previous statistic, is 1 in ~22.4 trillion.
And besides, there's no roll-over if it doesn't hit anybody!
Edited by Sonic on Friday 23 September 12:48
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