No antennae radiate all the power fed to them!
 

rickman wrote in :

No, cooling in space is very easy. Heat radiates quite well.

True but to get the best of it you have to have high grade energy to radiate.
(High temperatures, short wavelengths). If you could efficiently convert low
grade warmth in large amounts, to a small source of incandescent light, you'd
improve it. I'm not sure if such a process is easy or practical. To be worth
doing, it would have to cost less energy to convert than the difference in
that emitted for the two temperatures. It would probably have to use storage
too, for long slow inputs, short strong bursts of output, which complicates
things.

The problem is that low temperature superconductors are way too cool to start
with, so the supporting equipment would be as awkward as that on Earth, and
likely more so.

No antennae radiate all the power fed to them!
 

Lostgallifreyan wrote in
:

True but to get the best of it you have to have high grade energy to
radiate. (High temperatures, short wavelengths). If you could
efficiently convert low grade warmth in large amounts, to a small source
of incandescent light, you'd improve it. I'm not sure if such a process
is easy or practical. To be worth doing, it would have to cost less
energy to convert than the difference in that emitted for the two
temperatures. It would probably have to use storage too, for long slow
inputs, short strong bursts of output, which complicates things.


Never mind what I wrote just now. Can't beat entropy.

No antennae radiate all the power fed to them!
 

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.

No antennae radiate all the power fed to them!
 

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.

No antennae radiate all the power fed to them!
 

On 2014-11-02 11:01:54 +0000, Lostgallifreyan said:

Lostgallifreyan wrote in
:

True but to get the best of it you have to have high grade energy to
radiate. (High temperatures, short wavelengths). If you could
efficiently convert low grade warmth in large amounts, to a small source
of incandescent light, you'd improve it. I'm not sure if such a process
is easy or practical. To be worth doing, it would have to cost less
energy to convert than the difference in that emitted for the two
temperatures. It would probably have to use storage too, for long slow
inputs, short strong bursts of output, which complicates things.


Never mind what I wrote just now. Can't beat entropy.

No, but you *can* use a heat pump to move it somewhere else.

--

Percy Picacity

No antennae radiate all the power fed to them!
 

Percy Picacity wrote in
:

Never mind what I wrote just now. Can't beat entropy.

No, but you *can* use a heat pump to move it somewhere else.


Yes, sort of what I was getting at, I'm just not sure what qualifies as
'worth it' :) For example, you could store some low grade heat converting to
electric charge in batteries. This could then power a hot high current heater
to radiate overcoming local ambient heat from solar energy in a space
installation. If you had enough shade that would be likely less useful, it
might be cheaper to set up large low-grade radiators instead. it seems to me
that all kinds of compromises with cost, size, ambient conditions, will rule
what actually gets done.

Given that laser diodes can radiate a lot of power now, and be small with
very low mass, and convert upwards of 30% electrical input to light, they
might become part of a compact space-based heatsink. I suspect that 30% will
not be nearly enough to be usful in most cases because there will be other,
greater losses (laser diodes are some of the most efficient transducers ever
made).

No antennae radiate all the power fed to them!
 

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

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

No antennae radiate all the power fed to them!
 

"Brian Reay" wrote in message
...
It is nonsense, they can be no wave in the element due to it being a
conductor. He is confusing the I and V plots for waves.

OK, I realise now where your confusion has arisen. It is because I
was discussing what was necessary to set up a standing wave in the
first place, whereas you misunderstood and became confused because
you were discussing the state of affairs AFTER the standing wave had been
set up.

Perhaps if you read posts more carefully and were not so intent on scoring
points and abusing those with whom you deliberately disagree?

No antennae radiate all the power fed to them!
 

Jerry Stuckle wrote in news:m35chg$mlv$1@dont-
email.me:

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.


Not much, maybe. I just figured that their state would not be stable, that it
would take very little, from any source, to heat them to the point where the
problem started getting rapidly worse. Maybe it wouldn't be an issue if the
superconductor were 'hot' enough. -196°C is 77°C above absolute zero, so
maybe some of them will always stay cold enough with nothing but shade.

Heat sources might be unexpected though. If a thin wire got hit my a
micrometeorite, it would likely get stretched and heated pretty fast. So the
question might be what kind of margins exist for safe operation.

No antennae radiate all the power fed to them!
 

On 11/2/2014 9:11 AM, Lostgallifreyan wrote:
Jerry Stuckle wrote in news:m35chg$mlv$1@dont-
email.me:

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.


Not much, maybe. I just figured that their state would not be stable, that it
would take very little, from any source, to heat them to the point where the
problem started getting rapidly worse. Maybe it wouldn't be an issue if the
superconductor were 'hot' enough. -196°C is 77°C above absolute zero, so
maybe some of them will always stay cold enough with nothing but shade.


Actually, high temperature superconductors have been found at
temperatures as high as -135C. And in the shade, space is very cold,
even at Earth's distance from the sun, shaded items are very cold. Even
the moon, which will hold some heat, cools to -233C at night time.

Heat sources might be unexpected though. If a thin wire got hit my a
micrometeorite, it would likely get stretched and heated pretty fast. So the
question might be what kind of margins exist for safe operation.


I think the odds of this happening between now and the end of the solar
system are pretty slim. If a small wire could so easily be hit by a
micrometeorite, our satellites, space stations, rockets, etc., all much
bigger, would be in deep doo-doo.

No, micrometeorites are not very big, but their velocity makes them very
dangerous. Energy increases with the square of the velocity, and
micrometeorites move very fast.

--
==================
Remove the "x" from my email address
Jerry Stuckle

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