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No antennae radiate all the power fed to them!
Jerry Stuckle wrote in
: 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. I wonder if the ISS might be a place capable of doing tests like these. Parts of that must be in constant shade, so maybe some test of a space-based superconducting antenna is feasible. (I'm not ignoring what Jim said about having space to build a big, normal antenna, it's just interesting that there might be scope now to try this just to see what can be done with it. Also, given the cost of sendign heavy stuff out there, it might be viable anyway if it saves the need to do that so often). 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. Ok. :) Besides, never mind stretching, the superconductor would be brittle, probably. Would a swarm of partcles redirected from sun via some magnetic field, passing the antenna wire, be enough to heat it to the point of supercondcuting failure? I have no idea about this, it just seems that there might be a lot of energy, even if thinly distributed.. |
No antennae radiate all the power fed to them!
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. 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. The only external heat source in space is the Sun; solution, sun shade. If shaded, things get quite cold in space, cold enough for known superconductors to work. A hit by a micrometeorite would be rare, but likely catastrophic; heat wouldn't be your main problem. But again, the question is why bother? -- Jim Pennino |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
On 11/2/2014 10:49 AM, Lostgallifreyan wrote:
Jerry Stuckle wrote in : 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. I wonder if the ISS might be a place capable of doing tests like these. Parts of that must be in constant shade, so maybe some test of a space-based superconducting antenna is feasible. (I'm not ignoring what Jim said about having space to build a big, normal antenna, it's just interesting that there might be scope now to try this just to see what can be done with it. Also, given the cost of sendign heavy stuff out there, it might be viable anyway if it saves the need to do that so often). No, I don't think any part of the ISS is in "constant shadow". I believe it rotates as it orbits the earth, and different parts of it are in the shade at different times. I could be wrong, though - I've never been there :) 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. Ok. :) Besides, never mind stretching, the superconductor would be brittle, probably. Would a swarm of partcles redirected from sun via some magnetic field, passing the antenna wire, be enough to heat it to the point of supercondcuting failure? I have no idea about this, it just seems that there might be a lot of energy, even if thinly distributed.. Those particles, although moving quickly, would be too small to have much effect. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
No antennae radiate all the power fed to them!
Jerry Stuckle wrote in news:m36209$kk3$1@dont-
email.me: No, I don't think any part of the ISS is in "constant shadow". I believe it rotates as it orbits the earth, and different parts of it are in the shade at different times. I could be wrong, though - I've never been there :) Fair enough. I know that Apollo used to do the 'barbeque roll', but as far as I know there's less need of it on the ISS for whatever reason. Maybe they use the solar panels for shade part of the time, there's a lot of those... Or maybe it's in Earth's shadow often enough to get by... Or maybe it rolls constantly and I just had no idea. About particles, I don't know what sort of quantities there could be, or energies involved, but I'll settle for the realisation that an amount capable of causing heating would be long past rendering an antenna too noisy to use, probably. I suspect heating by remnant of mass coronal ejection might be the least of its worries. :) |
No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
wrote in : But again, the question is why bother? Well, to add to your list of Eternal Questions of the Past Century, you can add that one. :) It's far older actually, and has been asked of air travel, mountian climbing, exploring West Africa, Antartica, and probably bungy jumping. The jury's still out on that last one. The simple answer is: because it hasn't been done, or at least not by the person most wanting and able to do it. A better answer is: to find out what can be learned along the way, given that the destination is a new one. Most of science was built that way. Apples and oranges; we already know what will happen if one were to build an antenna from a superconductor. Fire up EZNEC and set material loss to zero; done. snip more apples and oranges -- Jim Pennino |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
Lostgallifreyan wrote:
wrote in : Apples and oranges; we already know what will happen if one were to build an antenna from a superconductor. Fire up EZNEC and set material loss to zero; done. Yeah, anyone with a map could say a great deal about the shape of West Africa based on ocean travel. Again, apples and oranges as we know EXACTLY and in DETAIL what would happen. My point isn't so much about antennas, as about exploring the easy availability of cold environments for superconductors in space. Easy availability measured in thousands of dollars an ounce to get stuff there. Not having to lug heavy coolers up there might be an offer someone cannot refuse, and that someone might come back with all kinds of discoveries, things no models or predictions are going out there to find. The only thing that makes a superconductor different is the lack of resistance. We already know exactly what that means and what we would do with them if room temperature superconcductors were available. Here are a couple of things: electric motors and generators that would be very close to 100% efficient, small, light, and lossless power transmission lines, lossless transformers, big honking magnets. -- Jim Pennino |
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