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PostPosted: Fri Oct 29, 2010 4:53 pm 
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EDG wrote:
http://www.solstation.com/stars/u722-05.htm

A very dim brown dwarf star has been discovered around 9.5 ly (about 2.9 parsecs) from Sol - it's so dim it's pretty much off the bottom of the existing scale, and may be one of the first examples of a Y-type object. If it's even a brown dwarf (it may not even be massive enough for that), it's cooled so much that it's almost indistinguishable from a dense jovian.



That's pretty cool (pun intended). BTW, I see that it was detected by IR observation. Makes sense of course.

EDG, based on your field of study, have you ever thought of putting together a little write up of IR detection tables for star ships (in system distances) IE: postulated advances in IR detection based on higher tech levels (ship & planet based) and how that effect ship detection. Trav ships using fusion PPs would have to be pretty bright objects...

Just a thought.

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PostPosted: Fri Oct 29, 2010 5:20 pm 
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DFW wrote:
EDG, based on your field of study, have you ever thought of putting together a little write up of IR detection tables for star ships (in system distances) IE: postulated advances in IR detection based on higher tech levels (ship & planet based) and how that effect ship detection. Trav ships using fusion PPs would have to be pretty bright objects...

Just a thought.


No, I haven't - largely because Traveller ships make no sense in that regard (sure, realistically they're going to generate a lot of heat - so where are their heat sinks? The usual excuse is "the heat is magically dumped into jumpspace" which throws that kind of detection up in the air)

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PostPosted: Fri Oct 29, 2010 5:27 pm 
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EDG wrote:
No, I haven't - largely because Traveller ships make no sense in that regard (sure, realistically they're going to generate a lot of heat - so where are their heat sinks? The usual excuse is "the heat is magically dumped into jumpspace" which throws that kind of detection up in the air)


No, from what I've read from the designers, it isn't dumped into jump space. It is radiated from the hull (I know the surface area isn't sufficient). In fact, MGT Main Rule book states that star/space ships CAN't hide because of the IR signature...

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PostPosted: Fri Oct 29, 2010 6:05 pm 
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DFW wrote:
No, from what I've read from the designers, it isn't dumped into jump space. It is radiated from the hull (I know the surface area isn't sufficient). In fact, MGT Main Rule book states that star/space ships CAN't hide because of the IR signature...


Which is why it's nonsense. With all the systems they have on board (plus a honking great fusion power plant) the ships would radiate too much heat to be able to do it just from the existing hull - they need to have huge heat-sink 'wings' like the ships in Transhuman Space, or the interior would cook (and if they're radiating enough IR to be detectable from AU away, then they are cooking already). OTU ships don't have this and neither do a lot of ships in SF - it's one of those armwaves that people tend to sweep under the carpet, like FTL travel.

Having such heatsinks would cool the ship off, and also produce a larger (and slightly less intense) IR signature since the heat is spread over a larger area.

I've split this discussion and moved this part to the gearhead section as a separate thread, since it's not related to the brown dwarf discovery.

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PostPosted: Fri Oct 29, 2010 7:57 pm 
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EDG wrote:
Which is why it's nonsense. With all the systems they have on board (plus a honking great fusion power plant) the ships would radiate too much heat to be able to do it just from the existing hull -[/color]


Yes, I stated that. However, that being said, we'll postulate something material that could radiate that much heat incredibly better (opposite of polished silver raised to X) as we have to put the heat somewhere.

Anyway, if you aren't interested I totally understand. I'll start researching it.

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PostPosted: Fri Oct 29, 2010 8:26 pm 
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Well, you're the engineer, this is more up your alley than mine :)

Though I think if you're postulating a miracle material that will radiate heat superefficiently from a limited area, you'll need to make it one-directional so it doesn't radiate back into the ship. And then think about how that affects the design of spaceships, since presumably they wouldn't want to have important stuff mounted on the hull by the radiators.

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PostPosted: Sat Oct 30, 2010 1:50 am 
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carbon has a high melting point of ~4000k
and graphene has a thermal conductivity of ~5000W/(m*K)
an emissivity of nearly 1 making it very very close to a blackbody radiator
this also means it would absorb lots of heat as well.

if I understand it correctly, then this is probably the best that can be done for finding a reasonable radiator material

Although, for the sake of other fixtures, I'd still try to minimize waste heat to keep radiator temps down a bit. Almost everything else in the universe has a much lower melting temp than 1500K. Unless I'm mistaken, a radiator at 1500K should allow about 275KW/m^2 to be radiated.

Multiple power plants for ships systems with the plants dedicated to drives being kept at 'idle' ( need warm start ) or shut down ( need cold start ) unless actually being used. Reaction thrusters dump heat when thrusting, aka, when its power plant is operating.
Ordinary systems powered by batteries/super-caps which are more efficient than a power plant probably is; less waste heat in that you'd be using stored energy as opposed to generating more.
Weapons' power plants shut down normally, battle stations involve a cold start to idle...warm start as part of weapon release.

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