h a l f b a k e r yWe have a low common denominator: 2
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Start with a reusable suborbital rocket. It just goes straight up for a few hundred kilometers, and then falls straight down, deploying parachutes at an appropriate altitude. (Rotation of Earth can be expected to cause the landing site to differ from the launch site.)
The payload of this rocket
is plain water. We select some item in orbit to clean up, and launch the rocket on an intercept course. About a minute before collision, valves are opened that let all the water spray into space, which will promptly turn into an expanding cloud of water vapor and ice crystals. Action and Reaction causes the rocket to no longer be on a collision course. The space debris plows into the cloud at something like 27,000kph, because it is moving at orbital velocity, and the cloud is merely rising some, with no significant orbital velocity. (It will also fall back to Earth in short order, but since it's just water, no problem.)
As you might imagine, the collison will be quite destructive to the orbiting debris. MORE, that collision will also sap a significant chunk of orbital energy from the debris. It can be expected to de-orbit and burn up in the atmosphere, within a few days or weeks (depending on original altitude).
NOTE: This Idea is best suited for Low Earth Orbit. Farther away, the velocity of orbiting objects is much less -- at the geosynchronous altitude, orbital velocity is less than 5000kph. Not to mention that that orbit is a lot harder for our spray-cleaner rocket to reach. Fortunately, most space debris is in LEO.
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As an alternative to the rocket, consider an electromagnetic catapult. Since we merely want to shoot a container of water upwards some hundreds (or maybe a few thousand at most) kilometers, and NOT put it into orbit, this catapult launching system can be rather shorter than the more-usually-discussed variety. And it is much more efficient than using rocket fuel. PERHAPS building such a catapult could qualify as a prototype, and would encourage the construction of a full-fledged orbital-launch system.
Orbiting debris
http://www.aoe.vt.e...gnSPs/ORDEM2000.pdf
Man is the animal that messes up everything he touches (including Nothing)! [Vernon, Oct 04 2004, last modified Nov 29 2004]
When water encounters a vacuum
http://www.madsci.o...984359705.Ph.r.html
Details of liquid becoming gas mixed with solids [Vernon, Oct 04 2004, last modified Oct 21 2004]
A proposed suborbital electromagnetic catapult
http://www.halfbake..._20Peaple_20Shooter
If a Vacuum Cleaner catapult is the prototype, and cheap orbital access is the goal, then this must be the pilot plant. [Vernon, Oct 04 2004]
New Chart of Debris
http://www.knowledg...cles/meteoroids.pdf
"The cumulative mass of these objects is approximately 2,000,000 kilograms ..." [Vernon, Nov 29 2004]
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How much water would be sufficient
enough to slow this debris to a proper
slower speed? |
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Would it be better to have a orbiting
laser vaporize one side of said debris
particle thus forcing it into a lower obit
with great force? |
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.......picturing homeless persons in spacesuits, drifting in orbit with all their belongings in a balloon with a door on it [see low cost space craft], collecting aluminum cans, dropped gloves and hardware, and redeeming said items for alcohol and food at the recycling center........... |
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[sartep], that will actually depend on the mass of the item of debris. But I can assure you that the collision will be explosive enough that at least some of the effect you would achieve with a laser will happen this way. |
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That's all I needed to know. + |
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As a non-expert, I assume that one unit of water will rob half the velocity of one unit of space junk. The question is, how wide is the scatter pattern in comparison to the mass and volume of a field of space junk? |
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[Laughs_Last], there are very few moving-together "fields" of space junk. The thing that makes this Idea half-baked is that so much junk out there is maybe 1/10 meter in diameter -- or even centimeter-sized, and each item we want to clean will require its own cloud of ice/vapor. {Thousands of spray-rocket-launches} equal {a ridiculously expensive proposition}, and so some sort of efficient launching system is going to be needed. |
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Next, planning and executing a collision course with space junk is something currently at the extreme limit of our capabilities. I thus suggested a cloud because it can expand to be big enough to ensure the junk runs into it. The more accurately we can plot a collision, the closer to time-of-impact we can spray the water -- and the less water will be needed, to do its job -- which of course lowers the cost of launching it. |
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An unpleasant idea just occurred to me.....aren't we risking filling near-earth orbit with clouds of ice cubes ? |
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"....oops.....Houston.......we have a problem......" |
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No, normzone, the water's going to slow and in the wrong direction. |
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Incidentaly, to reach 500km you need ~5 mega-jeules/kilogram. At 100% efishensency. |
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[going too slow and in the wrong direction] |
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Yeah, I understand that part, and I'm sure it's been said about a lot of objects. Some specific airliners come to mind, and I'm sure it's been applied to cars on freeways before. Not to mention more than one set of Halfbakery annotations. |
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I'm just envisioning one software glitch, and we've compounded our problem. |
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I think the Homeless Harvesting Heroes would employ more people, and make for more human interest stories in the news. It's easier to get funding from the public if there's people involved. |
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But I donated a water-soaked, ice-crystalized, burning upon reentry croissant anyway. |
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Edit: Vernon, your link to the Peaple Shooter made me want to ride it. But your link there to the story of the origin of Murphy's law led me to read the whole story. |
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And now we've come full circle. If we apply Murphy's Law here, we WILL sooner or later get a load of cubes in orbit. |
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So, I must reluctantly withdraw my croissant. While I'm spacejunk picking, I can nibble on it's burned fragments. |
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[normzone], the ice crystals formed by dumping water into vacuum will be too small to qualify as ordinary "ice cubes". They will fall back to Earth quite quickly, once gravity has sucked away their tendency to keep coasting upward on the launch trajectory. |
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[my-nep], it just so happens that 1 kilowatt-hour of ordinary electric power is 3.6 mega-joules, and a US dollar can buy several kilowatt-hours. The current hideous expense of putting kilograms into Space is simply proof of the hideous inefficiency of rockets. |
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[normzone], not even Murphy's Law can violate the Law of Conservation of Energy. It takes a LOT more energy to put something into orbit than to merely loft it high. |
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Of course, you could use anything, since it’s all going to fall back to earth in a few minutes. Explosively distributed sand would be better since it doesn’t evaporate or sublimate. |
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[ldischler], I would not want to be wherever that sand hits the ground, after falling back to Earth. I'm sure water will work just fine; even if it all evaporated into vapor (which it won't!) before being struck by the space debris, the cloud would still be a formidable obstacle. --AND, of course, we could just launch crushed ice...very little of which will sublimate before the collision happens. (But then "spraying" it becomes problematic...we don't want to "explosively distribute" it because that spreads/reduces the total amount of mass that the targeted space debris can encounter.) |
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If you sprayed powdered explosive, then a small drop may have a bigger effect.
Any unused powder would also be quite pretty at night, when it fell back to Earth. |
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//I would not want to be wherever that sand hits the ground//
...and I thought you knew what you were talking about! |
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[ldischler], I do know what I am talking about, but perhaps I don't know what you are talking about. I thought you wanted to loft sand instead of water. We both know that what goes up generally comes back down -- especially since that is part of this Idea. And so it remains true that //I would not want to be wherever that sand hits the ground//. Even one grain falling at terminal velocity will sting, uncomfortably. |
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No more than a raindrop, probably less. It's not a problem. The real problem is spalling particles from the debris, which just compounds the original problem. This will happen with either water or sand. |
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[ldischler], having a cloud in the way of the debris is a kind of insurance that even if the first collision causes spalling, all the spalled pieces will very likely still interact with other things in the cloud (gas or solid) and lose significant orbital velocity. Very little will then survive the plunge into the atmosphere, because of the remaining magnitude of orbital velocity. |
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Good grief. The concern is not what plunges into the atmosphere--it's what stays in orbit. Even something like a fleck of paint can kill an astronaut doing a spacewalk. Anyway, the idea is anticipated by RR's Star Wars program. |
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[ldischler], yes, I know that paint flakes are dangerous when moving at orbital velocity. I'd say some experimentation is in order, to see just how much (if anything) of a piece of space debris fails to de-orbit after encountering a suitably-placed cloud. We have no data yet, and I have a certain confidence that even the paint flakes will slow somewhat, due to secondary interactions (after the primary one loosed a bunch of paint flakes). |
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[zen_tom] no, sand particles that merely fall, with zero initial velocity, from say 500km up, will not be moving fast enough to burn up when they hit the atmosphere. Ordinary space dust that burns up starts out with multi-thousands kph velocity. |
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How'd I miss this one? Great idea, [V]. |
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Good idea ... if it would work. I'm
doubtful towards the theory behind it
though. |
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