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#2
November 3rd 14, 09:24 PM
posted to rec.radio.amateur.antenna
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No antennae radiate all the power fed to them!
On 11/3/2014 3:48 PM, wrote:
rickman wrote: On 11/3/2014 3:09 PM, wrote: rickman wrote: On 11/3/2014 1:07 PM, wrote: rickman wrote: On 11/2/2014 4:11 PM, wrote: Lostgallifreyan wrote: wrote in news 
The only external heat source in space is the Sun; solution, sun shade. Maybe not. I just did a bit of Googling for 'superconductors in space' minus quotes. There's a lot of statements abotu space missions ended because required helium or hydrogen coolant ran out, Yeah, the coolent ran out for the things that GENERATE a lot of heat and need to be cooled more than radiation can provide. Radiative cooling does not provide for a lot of cooling. and also of space having latent temperatures up to 100K, so a sun shade won't help a lot there with current materials. There really is no such thing as temperature in space as it is a vacuum. That is a gross oversimplification. The temperature of space is the temperature of the background radiation, even in a near vacuum. That is also an simplification. But not a gross oversimplification. True. Shall we go into why an ordinary thermometer exposed to the Sun at about Earth's distance from the Sun allowed to stabilze will read the tempurature of space as about 7 C and what are the unstated assumptions for this to happen? The number I found was about 4 °C. I believe it was posted with all the assumptions... I didn't see that post. If it has already be done, so be it. It is just the assumption that the object is a round, highly conductive, black body so that it absorbs all radiation hitting it and spreads the heat so it is isothermal and re-radiates it at that temperature the same in all directions. Sort of an inside out integrating sphere. This was the post where I quoted a formula that said the energy from the sun would produce 77 °K at about 13 AU. -- Rick |
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