rickman wrote in :

I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".


There's still such a thing as radiation resistance, I think, so it wouldn't
stay cold even there. Given the size of a body, there's a limit to how fast
it can get rid of heat at a given temperature.. I don't know the proper
terminology for it though. Anyway, at low tenperature, the rate it can
radiate heat is low, so it will quickly warm up out of low-temp
superconducting state.

On 11/2/2014 5:45 AM, Lostgallifreyan wrote:
rickman wrote in :

I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".


There's still such a thing as radiation resistance, I think, so it wouldn't
stay cold even there. Given the size of a body, there's a limit to how fast
it can get rid of heat at a given temperature.. I don't know the proper
terminology for it though. Anyway, at low tenperature, the rate it can
radiate heat is low, so it will quickly warm up out of low-temp
superconducting state.

Lol, radiation resistance is from the signal energy *leaving* the
antenna. It does not show up as heat!

You need to read up on the temperatures involved. Space is near
absolute zero. The Sun warms things in the solar system, but before
reaching Uranus even that heat drops to the point of N2 liquifying, 77
°K, still more than 70 °K above the temperature of space. So heat can
still leave liquid nitrogen easily and allow it to freeze at 63 °K at
one atmosphere.

--

Rick

rickman wrote in :

Lol, radiation resistance is from the signal energy *leaving* the
antenna. It does not show up as heat!


I already posted that I wasn't talking about radiation resistance as used in
antennas. I just meant that some object, at some temperature, is limited in
how fast it can get rid of its heat. (Also, assuming that even in space a
thing may get heated a little by something, no matter how well someone tries
to shield it, and that it won't take much to prevent a superconductor
working).

rickman wrote in :

You need to read up on the temperatures involved. Space is near
absolute zero.

I read less than an hour ago that the interstellar medium has latent
temperatures of up to 100K. For a 'vacuum' it has a lot of stuff floating
around in it, too.

Lostgallifreyan wrote:
rickman wrote in :

You need to read up on the temperatures involved. Space is near
absolute zero.

I read less than an hour ago that the interstellar medium has latent
temperatures of up to 100K. For a 'vacuum' it has a lot of stuff floating
around in it, too.

That is for energetic stuff floating around in some particular place.

If you were causght in a CME it would be a lot hotter than that, but
again that is stuff.

The background temperature of space is 2.7 K.


--
Jim Pennino

wrote in :

That is for energetic stuff floating around in some particular place.

If you were causght in a CME it would be a lot hotter than that, but
again that is stuff.

The background temperature of space is 2.7 K.


Ok, I just can't stop thinkling that stuff might get around out there in ways
that are hard to predict, or sheild from. My basic instinct, hearign ever
more reports of the complexity of nature out there, is that simple models,
like most bets, may be off. Maybe they just need a tiny tweak, or maybe
somethign big went un-noticed. I have no way to know, I'm just wary of simple
assertions about it now.

Lostgallifreyan wrote:
wrote in :

That is for energetic stuff floating around in some particular place.

If you were causght in a CME it would be a lot hotter than that, but
again that is stuff.

The background temperature of space is 2.7 K.


Ok, I just can't stop thinkling that stuff might get around out there in ways
that are hard to predict, or sheild from.

Get over it; we found out what's out there about a half century ago.


--
Jim Pennino

Jeff wrote in :

...or looking at it another way the dissipation in the radiation
resistance is not in the form of heat it is the power radiated into space.


Well, I did say I didn't know the terminology. On the other hand, I'm not
talking about antenna's radiation resistance. The only thing I'm sure of here
is that some body, at some temperature, can not emit heat faster than some
rate, and that superconductors in space will warm up too fast to stay
superconducting without support to cool them.

This discussion looked like it had strayed some way from the earlier talk of
antennas and radiation resistance.

Lostgallifreyan wrote in
:

Well, I did say I didn't know the terminology.

I just had a quick look at this:
http://en.wikipedia.org/wiki/Radiosity_(heat_transfer)

I've decided to just say I don't know and leave it at that. I am not going to
try to penetrate that lot. A person could get lost there forever.

On 11/2/2014 6:06 AM, Lostgallifreyan wrote:
Jeff wrote in :

...or looking at it another way the dissipation in the radiation
resistance is not in the form of heat it is the power radiated into space.


Well, I did say I didn't know the terminology. On the other hand, I'm not
talking about antenna's radiation resistance. The only thing I'm sure of here
is that some body, at some temperature, can not emit heat faster than some
rate, and that superconductors in space will warm up too fast to stay
superconducting without support to cool them.

This discussion looked like it had strayed some way from the earlier talk of
antennas and radiation resistance.


What would cause the superconductors to warm up? They have no
resistance, so it wouldn't be from internal means. And kept shaded,
there would be very little external heat applied.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================