Space-based power

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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MSimon
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Post by MSimon »

Grumalg wrote:
Turbogenerators run into the problem of mass from the get go. And getting them space rated is going to be tricky. Esp a zero G condenser. Steam plants on earth are leaky. No problem. You add make up water. Of course water wouldn't be used in space - still. Mfg. tolerances will have to be very tight.
No reason water has to be the working fluid. The mass could easily be reduced by a higher operating frequency. If you've seen and compared 60 Hz stuff to 400 Hz stuff you know what I mean. Suppose everything was built to run at 10's to 100's of Khz. The mass would go way down.

Not saying the mass would be tiny, but that it could be far less than what you'd expect from looking at 60 Hz equipment.
1. I said water wouldn't be used
2. It is the turbine mass that is the killer
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D Tibbets
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Post by D Tibbets »

Increasing the inclination of the satallites orbit would decrease the frequency , and possibly the duration and completeness of some of the eclipses, but not eliminate them unless high inclinations were used. I don't know how high of an inclination could be tolorated to keep the satallites steered antena on a single gound station (keep it above the horizen, etc). And the satallite would still be crossing the equater two times on each orbit.

Concerning power generation by heating a working fluid. A Sterling engine might be better than a steam turbine for several reasons. I don't think there is as much of a need for radiaters to handle the waste heat, it can operate at lower temperature gradiants. It is a simple self contained machine. It probably cannot match the energy density of a turbine, but when all the associated structure is considered it my be competative. It seems to be the engine of choice for at least some of the surface based solar thermal plants.


Dan Tibbets
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KitemanSA
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Post by KitemanSA »

D Tibbets wrote: A Sterling engine might be better than a steam turbine for several reasons. I don't think there is as much of a need for radiaters to handle the waste heat, it can operate at lower temperature gradiants.
ANY heat engine, Rankine, Brayton, Sterling, ANY of them will need a significant radiator. The Sterling will need perhaps a slightly smaller one because they tend to be closer to the ideal Carnot efficiency than either of the other two I mentioned, but that won't eliminate the need by a long shot.

By the way, A PV satellite needs a substantial radiator too. It is just good that the panels act as their own radiator.

gblaze42
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Post by gblaze42 »

MSimon wrote: You are correct (sort of). High peak power microwave generators are not uncommon. Continuous power in the 100 KW to 1 MW range is off the shelf. If we go down to 1 KW or so they are produced in the millions.

What we don't have is power receivers any where near that range.

So we can say that power generation will not be a serious obstacle. Reception (at reasonable efficiency and cost) is something else.

I've been giving it some thought, I'm not really seeing the problem that your stating. The major factor we are dealing with is power density of the beam, so many kw per sq meter, or how ever you want to cut it up. If you spread the microwave beam over a kilometer you would lower the power density of the beam, a mesh antennae thats spread across a kilometer would be doable, or you could use several smaller antennae. True it won't cover the entire kilometer but would get the highest percentage of the receiving area. The power density could be well under a kilowatt /sq meter, a much more manageable power level.

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Post by MSimon »

gblaze42 wrote:
MSimon wrote: You are correct (sort of). High peak power microwave generators are not uncommon. Continuous power in the 100 KW to 1 MW range is off the shelf. If we go down to 1 KW or so they are produced in the millions.

What we don't have is power receivers any where near that range.

So we can say that power generation will not be a serious obstacle. Reception (at reasonable efficiency and cost) is something else.

I've been giving it some thought, I'm not really seeing the problem that your stating. The major factor we are dealing with is power density of the beam, so many kw per sq meter, or how ever you want to cut it up. If you spread the microwave beam over a kilometer you would lower the power density of the beam, a mesh antennae thats spread across a kilometer would be doable, or you could use several smaller antennae. True it won't cover the entire kilometer but would get the highest percentage of the receiving area. The power density could be well under a kilowatt /sq meter, a much more manageable power level.
I'm not even concerned about power density. It is making 1E11 rectennas. If the diodes fail open - no problem. If they fail shorted you will have rectennas "popping" all the time even at space rated failure rates. Eventually the failed modules will have to be replaced. And you have to know which ones are bad. Even with rectennas rated at 100 mW it will be a problem.

I'd really like to see the plan.
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JohnSmith
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Post by JohnSmith »

If that's the biggest problem, I'd say we're pretty much golden. It would be almost trivial to design a mass production diode that is guaranteed to fail open. And not insanely difficult to produce locating beacons on failed rectennas. There's some company trying to build 'smart dust' sensors for border protection applications, and that seems to work ok.

I was browsing nextbigfuture's archive the other day, and noticed an article that might have some interest/application here. Space Bubbles are easy, big and cheap. It seems to me that they'd also make reasonably good spherical lenses, if you filled them with (extremely) low pressure gas. Cheap solar concentrators? Heck, maybe even a good way of focusing microwaves on the rectenna.

gblaze42
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Post by gblaze42 »

MSimon wrote:
gblaze42 wrote:
MSimon wrote: You are correct (sort of). High peak power microwave generators are not uncommon. Continuous power in the 100 KW to 1 MW range is off the shelf. If we go down to 1 KW or so they are produced in the millions.

What we don't have is power receivers any where near that range.

So we can say that power generation will not be a serious obstacle. Reception (at reasonable efficiency and cost) is something else.

I've been giving it some thought, I'm not really seeing the problem that your stating. The major factor we are dealing with is power density of the beam, so many kw per sq meter, or how ever you want to cut it up. If you spread the microwave beam over a kilometer you would lower the power density of the beam, a mesh antennae thats spread across a kilometer would be doable, or you could use several smaller antennae. True it won't cover the entire kilometer but would get the highest percentage of the receiving area. The power density could be well under a kilowatt /sq meter, a much more manageable power level.
I'm not even concerned about power density. It is making 1E11 rectennas. If the diodes fail open - no problem. If they fail shorted you will have rectennas "popping" all the time even at space rated failure rates. Eventually the failed modules will have to be replaced. And you have to know which ones are bad. Even with rectennas rated at 100 mW it will be a problem.

I'd really like to see the plan.
It maybe more doable if they use a transformer and instead of changing to a DC voltage which a H-bridge diode setup would do, just lower the AC wave form, possible into something more usable like 60HZ.
1E11 rectenna's does sound a way to many.

But as you said, I'd like to see some kind of plan.

MSimon
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Post by MSimon »

It would be almost trivial to design a mass production diode that is guaranteed to fail open.
Semiconductors don't work that way - generally. But if you have a paper on how to do it I'd love to see it. In programmable semiconductors they zap diodes with high energy pulses and they "fail" shorted. With very high reliability. If failing open was an option why are no diode programmable semiconductors designed that way?

What I expect to happen - diodes will fail shorted. The shorts will draw a lot of current. The current will vaporize enough of the diode structure to cause an open. It will be important to keep those trace elements in the diodes like arsenic and boron contained. And you will have to prove it to EPA satisfaction.

I do believe that 2016 is tout fluff to attract marks.

Unless our current administration decides it is a "shovel ready" green project. In that case the "investment" could pay off handsomely.
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MSimon
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Post by MSimon »

One thing to keep in mind is that I was very sceptical of the General Fusion reactor. Until they released enough data to show that it was on the edge of possible. Once I had the data I ran the BOE numbers and changed my mind.

So far we have nothing here.
Engineering is the art of making what you want from what you can get at a profit.

JohnSmith
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Post by JohnSmith »

No paper, but I'm not sure I see the problem. Just design a package with redundant diodes, and a circuit that cuts the whole package out of the bridge if a diode fails. The chances of two or more diodes failing simultaneously is pretty small.
Even if somehow all of them do go, and all of them fail shorted, you're not going to end up with many of these (all fail) events in the lifetime of the rectenna. Add that to the fact that most semiconductor devices are packaged in plastic, and there's not much release of hazardous materials.
So you go out and fix it, and everybody's happy again.

And as for why nobody programs semiconductors for fail open, I'm willing to bet that it's because fail short is much, much easier to accomplish. And why would you make it harder than you have to?

Boron's not a good example of a hazardous material. Not unless you're allergic to laundry soap, anyway.

MSimon
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Post by MSimon »

JohnSmith wrote:No paper, but I'm not sure I see the problem. Just design a package with redundant diodes, and a circuit that cuts the whole package out of the bridge if a diode fails. The chances of two or more diodes failing simultaneously is pretty small.
Even if somehow all of them do go, and all of them fail shorted, you're not going to end up with many of these (all fail) events in the lifetime of the rectenna. Add that to the fact that most semiconductor devices are packaged in plastic, and there's not much release of hazardous materials.
So you go out and fix it, and everybody's happy again.

And as for why nobody programs semiconductors for fail open, I'm willing to bet that it's because fail short is much, much easier to accomplish. And why would you make it harder than you have to?

Boron's not a good example of a hazardous material. Not unless you're allergic to laundry soap, anyway.
Your solution is going to raise the cost per diode from .1 cent to 1 cent. A deal killer.

Space rated components have failure rates of 1 part per million hours. If you have 1E11 diodes that is 1E5 failures per hour. About two thousand a minute. But it costs a lot to get space rated components. You have to do a lot of burn in and testing.

Boron is rated 50 out of 400 on the EPA's toxic materials list.

Now obviously my numbers may not be correct. Reliability may be 100 times better. It will still cause problems. And that is just for the diodes. What about bonding them to the circuit? The circuit board? The connections to the power converters. The failure rate of the capacitors required near the diodes. etc. etc. etc.

Packaged in plastic? You obviously have never seen a semi-conductor explosively fail.

And how pray tell do you get redundant microwave diodes in a circuit with out wrecking the circuit impedances? Very important. And then you have a switch capable of switching at microwave freqiencies for under .1 cent each. And a decider circuit. Each of which (the switch and decider) that have failure rates many times higher than the diodes. Then they need to be tested in production further raising the costs. You make a batch of semiconductors and then pick out the good ones.

Just letting the diodes pop until they sufficiently degrade power handling may be the low cost option. If you have a robot capable of doing the testing. You will need total test rates on the order of 1E8 per hour to get the job done in a reasonable time. With 1,000 robots that is 1E5 components per hour per robot. 300 a second all while moving around and changing out the bad ones.

I'm not saying the problems can't be solved. What I'm saying is that it will not be trivial. And it may not be economical.
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JohnSmith
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Post by JohnSmith »

Simon, my solution was just a proof of concept. I'm 99% sure that there's a hundred better ways to implement it.
I have seen a semiconductor fail explosively; In a class of 100 electrical engineers, you always end up with someone crosswiring things, usually to the highest power rail available. I just don't think that these components would have a high enough voltage across them for that to be an issue. Not to mention, the idea is to fail open, right?
Boron compounds are reasonably safe.
All that said, I think you've convinced me there'd be a reasonable engineering challenge. Good thing we've got lots of engineers, eh?

JLawson
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Post by JLawson »

If I recall correctly, one of the major concerns with SPSs beaming power to earth was the environmental effect of so much power onto a small area. Rectenna arrays were proposed for the Southwest - on the assumption that it was already a desert so what was the problem?

But with the current ecological worries (With Feinstein blocking solar power arrays) I don't see THIS concept getting far at all. Visions of microwaved free-range squab falling from the sky comes to mind... and if I can think of it, you can bet the eco-nuts will scream about it and other possiblities even more remote and implausible.
When opinion and reality conflict - guess which one is going to win in the long run.

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Post by Roger »

JLawson wrote:
But with the current ecological worries (With Feinstein blocking solar power arrays) I don't see THIS concept getting far at all.
I agree that this concept wont go far..... for a different reason...within the next 20-25 yrs. For me it is the issue of launch capacity. We might some pilot programs over the 2 decades, but thats it.

When I look at SpaceX, for example, I just dont see kerosene rockets, or even solid rockets being a viable vehicle to place significant infrastructure in orbit. In other words I dont see an oil based economy/society being capable of this. Now - on the other hand, a fusion powered society could do this in a heartbeat.... bu then the question becomes, "Why would you?".

I far prefer QED/Polywell PB&J fusion byproducts to a rough equivalent of kersone or solid fuel segments. >wink<


BTW at daily Kos, Vladislaw posts everyday promoting space programs and such, we've had some discussions on space based power, most folks agree, A Net power polywell makes the immediate desire, or need, or reasoning to go space based somewhat moot.

Heres a link to his Sunday article:
http://www.dailykos.com/story/2009/4/26/1247/36192

Now thats not to say that as we colonize the solar system, systems like these wont be deployed in other locations, especially if we can produce the panels in space. With a PV panel factory on say...... the Moon, one then has many interesting options.

If polywell gives us "fusion power", it also gives us the solar system. And we truly become a space faring race.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

JLawson
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Post by JLawson »

Well, Roger, I'm keeping my fingers crossed that Polywell works. As far as space travel goes - I'd LOVE to see NASA just toss everything into the public domain, and guarantee elimination of a lot of the regulatory load that's currently a barrier to getting to orbit.

Sometimes I see our current times like a game - each level gives you a chance (not a certainty, mind you) of collecting enough resources to bootstrap your tech to the next level, and start working on the level beyond THAT one.

We had wood at the beginning of the Industrial Revolution, but that wasn't enough to finish it so we turned to coal. Coal worked well enough, but when cars came in oil worked much better. Coal and oil (and hydro) got us electricity and that worked well enough to get us started on nuclear... and there we've stalled. We're working on fusion, kind of... but if we don't get fusion we don't get off the planet. (Which is perhaps the goal of the game?)

And sometimes it seems like we're actively sabotaging our own efforts. Will we win through despite the best efforts of those who would see the entire game lost?
When opinion and reality conflict - guess which one is going to win in the long run.

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