beowulf in space

[Joel Jaeggli]

On Mon, 14 Apr 2003 chettri at gst.com wrote:

> Has anybody considered the theoretical aspects of placing beowulfs on a 
> cluster of satellites? I understand that communication will be slower AND 
> unreliable,

Communication to satellites needs to be neither slow nor unreliable, it is 
generally fairly high latency... It can be quite expensive.

There are clusters of computers in space. they generally aren't what you 
would consider heavy computation platforms...

The biggest issues with with computer resources in space are:

mass - 	a large sattellite such as the hughes galaxy 4r bird is around 
	2500kg for everything that's half the mass of the ups that backs 
	up our racks. every gram you send up costs you.

power - solar power and long life cadmium batteries mean your whole 
	platform has to run on pretty thin resources. again using 
	something like galaxy 4r which is a very powerful satellite 8800 
	watts is what you get max to power everything... Thats with a 26 
	meter span of galium arsenide solar cells. most of the power is 
	going to communications equipement in the case of galaxy 4r r that 
	would be 24 c band at 40w each and 24 ku at 108w each

radiation hardening - without 50 miles of atmosphere overhead we're kinda 
	close to the sun and gamma ray bursts from other parts of the 
	galaxy are kinda hard on the equipment.

thermal management - air cooling doesn't work given no atomosphere... even 
	on something like the iss hot air doesn't rise in microgravity,
	you have resort to fairly extreme measures to deal with the 
	thermal management issues. if you see the laptops on the shuttle they're mostly 
	pentium class thinkpads with some fairly serious mods. There's
	mission specific equipment as well, but you won't find a rack of 
	dual xeons floating around due to thermal issues alone 
	(disregarding mass or power requirements).

expected service life - if you plan on go to the expense of putting it in 
	geostationary orbit you're probably planning on keeping it up 
	there for a minimum of 10-15 years, so it has to still work
	after a decde in a hostile environment, and upgrades and 
	service calls aren't in the plan.

It's pretty easy to spend a billion dollars by the time everything is said 
and done putting up a large satellite. you generally try to loft only 
what's critical to the mission of the satellite.

> and it would restrict the set of problems that could be solved. I'm looking 
> for papers/tech reps etc on the subject.
> 
> Regards,
> 
> Samir Chettro
> 
> 
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Joel Jaeggli	      Academic User Services   joelja at darkwing.uoregon.edu    
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