Interesting! In my story I have a big ball of something very much like this orbitting the Earth to clean up space junk. Only different is I made mine out of carbon instead of silicon.
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The ball in my story is about 100 KM in diameter. As it passes overhead it casts a shadow as big as Los Angeles. After a few days, a good fusion blast would start it spiraling into Earth's atmosphere, carrying all the captured debris with it.
FYI Chad: The "Orbital Debris Collector" (ODC) was the original opening shot of the story our group is now critiquing, back when it was also a teleplay.
It started in 1966, when astronaut Michael Collins lost his camera on a Gemini flight. The camera is still up there. My story gave a narration of all the great human accomplishments that the camera saw over the next 200 years. Then the camera smashed into the ODC and was totally destroyed.
Then my story began.
In the teleplay version, I had the camera witnessing a montage, a bit like the opening of the TV show Enterprise. It lead to a visual joke, with the ODC looming over the Earth like the Death Star. A fast zoom would show that a tiny spaceship was orbiting just in front of the ODC, its bored crew broadcasting warnings that the ODC was a navigation hazard.
Then the viewer would realize that the giant sphere looming over the Earth was friendly.
In the current version of the story the ODC might not show up until book 2.
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Impressive. Most impressive. (But you're not a Jedi yet.) Ta for sharing, Doc, although I'll be suing you, of course, for the damage done to my brain as it was overloaded by a thousand ideas all at once. JK
Posts: 503 | Registered: Sep 2000
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Actually, Chad, it was in a backwards equitorial orbit, east to west. It could only be so big and only stay up so long because it was such a navigational hazard, and my future presumed a lot of spacecraft lifting off, landing, and orbitting all the time. The purpose of the ODC was to reduce orbital debris from crowded orbital paths, not eliminate it altogether.
Left on its own, inertia from imapcacts of debris would eventually cause it to drop out of orbit and burn up. The purpose of the manned ship orbiting just in front of it was to warn traffic that this huge obstacle was coming their way. In case of emergency, the crew would thrust their ship away from the ODC at maximum acceleration. This would send their ship blasting out of orbit, and drop the ODC right into the atmosphere, where it would burn up.
I eventually decided that an unmanned ship could do this better than a manned ship. A manned ship can't pull more than about 9 gees for any length of time, while an unmaned ship could pull a lot more. Thus an unmanned ship could de-orbit the ODC much more quickly than a manned ship.
Another problem is that no one who read the scene in the teleplay understood that it was a double spoof of Star Wars and 2001: a Space Odyssey. The joke used visuals and music but no dialogue. A giant looming sphere casting a shadow on the Earth, ominous music, a spinning bone, a waltz . . . no one saw the humor but me.
So that scene is no longer the opening of my story, but the ODC will still show up now and then for periodic orbital hygene. Any time there's an orbital cleaup going on, everyone on Earth will be able to see it.
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No, though they would provide the useful effect of keeping it aligned "vertically" so as to sweep out a maximum of the debris in those orbits it does traverse.
Posts: 8322 | Registered: Aug 1999
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Doc, I see you've thought this out! Sorry for going off half-cocked.
As for tidal forces, calculations like the roche limit, etc, only apply to objects without mechanical strength -- just gravitational. Reenforce your ODC with some sort of fibers (boron, kevlar, diamond-like-carbon -- or, hell, steel is still the dominatnt engineering material, and will be for thousands of years, simply because it's versital and cheap.)
Thus, it will have the strength to not get tidally... "disrupted."
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Thanks for the input, gang, though I honestly did start this thread just to point out the new "lightest solid in the world."
Chad, I made the whole thing out of carbon because the technology I presumed would synthesize the ball atom by atom, and single element molecules would be easier than multiple element molecules. It would hold itself together without gravity, though I suppose there is no reason why it couldn't be reenforced with synthetic diamond fibers. Those have the advantage of being strong enough to hold it together, but combustable enough that they will burn up before they get the chance to rain firey death on unsuspecting pedestrians.
The idea is that the ball is not very dense, and objects hitting it slow down as they pass through. Even if the objects are not stopped inside the big ball, by the time they exit their speed will be slow enough that they will soon fall out of orbit and burn up.
My greatest concern was keeping big chunks of the ODC ball from breaking off and forming hazards of their own. The obvious solution is to start the ODC in a high orbit that is decaying. After a few days it will burn up on its own. Great idea, but it still leaves no role for the four man crew I wanted to employ. So the role of the ODC will be smaller.
If you want to use carbon, take a look at something like nano-tubes built from Buckminster-Fullerences. It's not all that far off - though whether you'd want to constantly destroy such an engineering feat...
Using aerogels to collect tiny particles in space seems a little pointless for cleaning purposes - it's objects of 10cms or more that post a serious threat to spacecraft - and the aerogel isn't dense enough to capture those, especially considering the massive velocities involved.
Recommend you consider the notion of a structure based on superconducting nano-tubes - magnetically charged it would be able to use the earth to act like a dynamo to generate its own power. If it's able to reach a field strength of a couple of Tesla, it should be able to magnetise and attract any form of debris, and keep it fixed to the overall structure.
Just a thought, anyway!
[This message has been edited by Chronicles_of_Empire (edited June 26, 2002).]
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Seems like only ferromagnetic or ferrimagnetic materials would be attracted to a magnetic doohickey.
Most space debris would be either paramagnetic or diamegnetic (ceramics, stainless steel, aluminum, etc), and thus not affected or only minimally, methinks.
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No - that's why I specifically mentioned that a high field strength is required. If you apply a field of a few tesla you directly affect the constituent electron spins of any material, and manipulate accordingly.
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That's how a MRI works, I think -- it effects the nclear spins of the H atoms or something. But, magnetic field, IIRC, decays at an inverse-square law, so it would only get the materials that come very close to it.
Hmmm... my specialty is mechanical properties, not magnetic properties. Maybe I should go brush up; this is bothering me now...
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Yes, it is an inverse-square law - but I figured the device was supposed to travel over a large distance over a long period.
Personally, though, I'm sure there would be better ways to clean up space debris than anything suggested here - I just wasn't impressed by the aerogel method and wanted to modify the design concept!
Another alternative would be to attach a VERY long cable to a vacuum cleaner, and then fire it into orbit...
First, there is already a lot of traffic in low Earth orbit. In a couple of centuries I expect it to be pretty darn crowded. So you'd only be able to do debris cleanup for a few hours every year. You'd need a device that could sweep a very large path yet be disposable.
Second, the ODC does not need to capture any debris. It only needs to slow it down a little bit. That's why I had the ODC orbitting east to west, since man-made objects generally orbit west to east. Even if a collision breaks off pieces of the ODC, those pieces will not remain in orbit. I can't imagine any exchange of inertia that would leave the debris, the ODC, or the broken pieces in a stable orbit.
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Doc is right, the areogel would work just fine at a low cost, whereas an ultra strong magnetic field would be much more expensive, dangerous, and maintenance intensive.
Posts: 8322 | Registered: Aug 1999
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Actually, current technology might be better suited to the magnetic solution. It won't work very well, but the areogel would be awfully expensive. Getting it to orbit would be the hard part.
Now, when we've got the technology to manufacture it in orbit, then the aerogel might be a good idea for orbital debris cleanup. But to make the device I described, it would require a way to get 1.6 quadrillion kilograms of silicon dioxide into orbit!
Actually, I didn't post the link just to talk about my idea for orbital debris cleanup. I posted it so that the creative minds around here might think of additional uses for the world's lightest solid. Keeping in mind that it can endure temperatures up to 2,600 degrees F, what could you do with this "frozen smoke?"
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Aye, that's what I was thinking (firefighters). I would think it could also be used to replace those heavy tiles on the space shuttle that comprise its heat shield. A few layers of that stuff interwoven (or, I suppose, stacked) so that there are NO gaps would make a pretty light shield...cut the cost of lifting it into space considerably....umm...Fire retardant netting? Drop a big net of that over a flame and I suppose it could smother the fire. Really though, until they can solidify the material it has very few uses. Sponges don't work well for anything but sponging.
Posts: 18 | Registered: Jul 2002
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Wouldn't work for a reentry shield...the stuff is too soft (you can poke your finger right through it). And if you compact it, all you get is a sort of finely powdered glass.
If you try to use it to insulate clothing, it would break down under the physical stress and crumble into powder pretty quickly. It could put out wildfires, but how would you deliver it? The stuff is so light that the updraft from a good blaze (or even a campfire) would keep it from landing anywhere near the fire.
It would be better to use it as fireproofing and insulation in buildings. I should also mention that it has a really high dielectric, so it could be useful in some high voltage applications...I suppose.
As for manufacturing it in space...the stuff would actually be cheaper and easier to manufacture in space, and there's plenty of silicon dioxide in space already...though not in near Earth orbit. You would have to ship packets from the moon (quite cheap if you build a "rail launcher") or from the asteriod belt (quite exensive, really). A magnetic array would need to be huge, with thousands of individual magnetic coils, to accomplish anything, and because a magnetic field is a naturally "conservative" phenomenon, if you just left the magnets on (or in an ossillating state so that they would repel any conductive material) then objects coming in would tend to either "bounce" or "refract" through the array, changing their direction but not their energy (unless they actually hit and damage the array). So you would need some sort of active sensor and targeting array, to tell the individual magnets when to turn on and off to deflect objects into deorbiting trajectories. And for a certian set of tricky inbound trajectories the array would actually tend to boost objects into higher and more eccentric orbits rather than deorbiting them. Not to mention that the thing would have virtually no effect whatsoever on non-conductive junk, like heat shielding tiles and crud like that.
A better solution would be to use a series of "Star Wars" type satillites, using particle beams to "shoot" down individual objects by heating the object on its leading side, thus vaporizing a small amount of the object and giving it a decelleratory "nudge" that would deorbit it. This does share the "tricky inbound" problem, though.
Make the stuff on the moon. Use a mass driver to launch a continuous stream of it into a low, East-to-West Earth orbit. This is not a stable orbit, but a spiral toward the Earth's atmosphere.
This trail of moondust spiraling toward Earth would collide with a LOT of stuff! It might be great for clearing orbital debris. But two questions remain:
Could the human race tolerate such a thing? This type of cleanup might require all spaceships and satellites to avoid a huge portion of low Earth orbit for days at a time.
What about environmental impact? What would happen to the Earth's environment if you burned many quadrillions of kilograms worth of SiO2 in the atmosphere? Surely something bad would happen!
quote: What about environmental impact? What would happen to the Earth's environment if you burned many quadrillions of kilograms worth of SiO2 in the atmosphere? Surely something bad would happen!
I don't know... but I once read MINING THE SKY, by Lewis, and he discusses ideas along these lines... perhaps we should refer to it.
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It would be a bad idea to inject dust into orbit like that, eventually you would need to use a large solid going the other way just to clean up all the dust. Besides, if you just injected the dust cloud, you wouldn't slow down low orbiting junk enough to deorbit it. Making a large solid object is a necessity.
As for environmental hazards, SiO2 is pretty harmless, 'tis just fine sand, after all. You could dump any amount of it on the Earth, as dust, and never have the slightest impact on the environment. Meteors and other infalling celestial junk already inject a lot of metals and such into the upper atmosphere naturally. This stuff would be a lot less harmful than that.
quote:What about environmental impact? What would happen to the Earth's environment if you burned many quadrillions of kilograms worth of SiO2 in the atmosphere? Surely something bad would happen!
Wouldn't quadrillions of kilograms of SiO2 in the atmosphere cause something like a nuclear winter?
Ever hear of The Year without a Summer? It happened around 1813 after a volcano in the East Indies erupted and put tons of particles into the atmosphere. (I think the volcano was named something like Tamboro--it was much worse than the more famous eruption of nearby Krakatoa.)
One of the reasons the impact of a large asteroid (or comet, or whatever) would be so disastrous to life (human or otherwise) on out planet is not so much that it would destroy whatever it hit, but because the impact would throw huge amounts of SiO2 into the atmosphere, and that stuff would cut off the light and heat from the sun all over the earth. Not nuclear winter exactly, but just as bad in its way.
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