typodupeerror

## The Space Garbage Scow, ala Cringely221

Posted by Soulskill
from the dream-big dept.
An anonymous reader writes "Robert X. Cringely once again educates and amuses with his take on how we could clean up the garbage that's in orbit around Earth. I cannot vouch for his math, but it makes sense to me. Quoting: 'We’d start in a high orbit, above the space junk, because we could trade that altitude for speed as needed, simply by flying lower, trading potential energy for kinetic. Dragging the net behind a little unmanned spacecraft, my idea would be to go past each piece of junk in such a way that it not only lodges permanently in the net, but that doing so adds kinetic energy (hitting at shallow angles to essentially tack like a sailboat off the debris). But wait, there’s more! You not only have to try to get energy from each encounter, it helps if — like in a game of billiards or pool — each encounter results in an effective ricochet sending the net in the proper trajectory for its next encounter. Rinse and repeat 18,000 times.'"
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## The Space Garbage Scow, ala Cringely

• #### Make sure. (Score:5, Insightful)

on Sunday November 15, 2009 @11:24AM (#30106166) Homepage

That this doesn't break up any debris into more parts - or cause the "net" to break and provide additional pieces of junk circling the earth.

• #### Re: (Score:3, Interesting)

Mod parent up. In addition, tiny specks acting as micrometeorites are probably a much bigger problem than the bigger avoidable pieces. Hitting all that big junk together in a net at orbital speeds will probably result in even more micrometeorites.
• #### Re: (Score:3, Informative)

I suppose you're catching stuff in a net travelling in the same direction as the junk so it'll be a gentle catch rather than a hard collision. That shouldn't create any more micro bits of shrapnel.

• #### Re:Make sure. (Score:4, Insightful)

on Sunday November 15, 2009 @07:54PM (#30110688) Homepage

Actually, our boy Cringely wants the net to travel in a polar orbit to catch junk that's mainly traveling in a equatorial orbit. Think of a bit of junk t-boning your net at 17,000 MPH.

• #### Re: (Score:2, Insightful)

It won't work... there are too many unknowns and no way to fix the scow when (read inevitable) things go wrong. The scow approach can really only be designed upfront and then implemented after the fact.... risky. The lasers idea that he dismissed out of hand early on in the article actually makes more sense. Except that the lasers aren't intended to vaporize the entire object, but a tiny fraction to induce a deceleration so that the orbit can decay faster. The laser approach can go through spiral devel
• #### Wouldn't that be bad when it re-enters? (Score:2)

Wouldn't it be bad catching all of the space debris in a giant net, when the net itself will eventually come back down to earth. Individual space junk coming out of orbit isn't as bad since it's not all falling in the same place and it's small enough to mostly burn up in the atmosphere, but if you've got this huge net there's a lot more junk to burn up with a much more localized crash site.

Plus this thing bouncing around like a billiard ball seems likely to catch something that isn't junk...
• #### Re: (Score:3, Interesting)

The risk of snagging one of the numerous live satellites would certainly be a problem. Re-entry, though, could be handled by picking an unloved chunk of ocean(hardly a limited resource) and just aiming for that.
• #### Re: (Score:2)

do not tell that to sea shepherd...

• #### Re:Wouldn't that be bad when it re-enters? (Score:4, Funny)

on Sunday November 15, 2009 @11:42AM (#30106338) Journal
We'll just tell them that it is our new orbital anti-whaling weapon...
• #### Re:Wouldn't that be bad when it re-enters? (Score:4, Informative)

on Sunday November 15, 2009 @11:41AM (#30106330) Journal

The problem with space junk is that there's thousands of piece of it flying around that can damage spacecraft, re-entry isn't really the problem. That's actually preferable to losing a few of your spacecraft to loose pieces of material in orbit.

• #### Re:Wouldn't that be bad when it re-enters? (Score:5, Informative)

on Sunday November 15, 2009 @05:22PM (#30109496)

Just wanted to point out that for the first time in the history of slashdot, you correctly spelled "losing" and "loose" in the same sentence. The content of your point is good too!

• #### Re:Wouldn't that be bad when it re-enters? (Score:5, Interesting)

on Sunday November 15, 2009 @12:28PM (#30106710)

Who says it needs to re-enter? If the bits of junk are all lodged in a larger net structure which behaves in a predictable manner, it could just be left up there as a sort of orbital junkyard. The proposed designs for a space elevator require a chunk of ballast to keep the tether taught... Why not a bunch of discarded booster shells and such, tacked together? It took a lot of energy to get that stuff up there... Why waste it?

• #### Re:Wouldn't that be bad when it re-enters? (Score:5, Insightful)

on Sunday November 15, 2009 @12:54PM (#30106896)

I'd mod you up if I had points. Apparently Cringely hasn't thought about how valuable a few hundred metric tons of refined materials would be in orbit. Instead he says "Nope, we have to gather the stuff and bring it back to Earth." He fails to realize that _someone_ would certainly pay for access to all of that material. He also fails to realize that a polar orbit intersecting an equatorial orbit will result in a relative velocity of about 10 kilometers per second, which equates to 50 megajoules per kilogram. Carbon nanotubes or not, nothing is going to withstand such a large amount of energy in such a small area, repeatedly, along with whatever centripetal forces are acquired from off-center hits from debris.

A visionary he might be, but a practical engineer he is definitely not.

• #### Re: (Score:2)

50 megajoules per kilogram is only a problem if the net is not affected by the impact. Have the net take on some of the momentum of the impact and you can absorb a lot of the energy. You can also use an elyptical orbit to decreases the relative velocity.
• #### Re:Wouldn't that be bad when it re-enters? (Score:5, Interesting)

on Sunday November 15, 2009 @02:03PM (#30107590)

At speeds above Mach 8.0, you can drive a pencil through a 100mm armor steel plate - even the pencil tip stays intact and sharp.

At 36,000km/s (equal to Mach 36 at sea-level), the net or carbon fiber construction will not even have a chance to absorb anything. The net itself might be able to absorb this momentum and energy level at a whole, but I seriously believe a metal piece will just blast right through it, instantly shearing the filament at molecular level. The inertia of a single carbon nanotube will probably be all that is needed to cleanly cut it off.

• #### Re: (Score:2)

At speeds above Mach 8.0, you can drive a pencil through a 100mm armor steel plate - even the pencil tip stays intact and sharp.

At 36,000km/s (equal to Mach 36 at sea-level), the net or carbon fiber construction will not even have a chance to absorb anything. The net itself might be able to absorb this momentum and energy level at a whole, but I seriously believe a metal piece will just blast right through it, instantly shearing the filament at molecular level. The inertia of a single carbon nanotube will probably be all that is needed to cleanly cut it off.

But if it causes these small pieces of metal to fall towards the Earth, where the atmosphere will do a lot of the work for us, isn't that good enough?

I'd say "away from the Earth" too, but I think I'd rather not like to lose a large amount of metal to the interplanetary void...

• #### Re: (Score:3, Informative)

Good point. Probably should be km/h?

• #### Re:Wouldn't that be bad when it re-enters? (Score:5, Insightful)

on Sunday November 15, 2009 @03:50PM (#30108740) Homepage Journal

At speeds above Mach 8.0, you can drive a pencil through a 100mm armor steel plate - even the pencil tip stays intact and sharp.

Though I completely agree with your overall point, I'm curious if you have a citation for this sentence. The plate and pencil are in relative motion, yet apparently the impact drills a hole through the plate without even dulling the pencil? I tried googling for an experiment like this with no luck. Now I'm just trying to figure out what insane combination of high-speed photography and a hypersonic wind tunnel with a "pencil of death" feature would be required for proof...

• #### Re:Wouldn't that be bad when it re-enters? (Score:5, Funny)

on Sunday November 15, 2009 @11:45PM (#30112040)
I wonder if this means that if you hurled 100mm armor steel plate @ mach 8.0 at a pencil if the pencil would survive-- perhaps we should be investing in pencil-based armor
• #### Re: (Score:2)

The contents that would be accumulated wouldn't be compressed into a 'hard' meteor as it re-entered the atmosphere. After a few seconds it would break apart into numerous pieces with a huge surface area. With slight considerations to have it re-enter over an ocean, the risk from these items would be very very low.

• #### Cringeley Amuses (Score:4, Insightful)

<folderol@fancypants.org> on Sunday November 15, 2009 @11:30AM (#30106226) Journal

I thought they were just in the early stages of establishing a ring-world, in terrestrial orbit. Oh well...

There will of course, be no such mission, headed by NASA, or any other fraction of the Federal United States. That banana republic operates on such a scale, only when there is substantial room for contractor and supplier rip-off. If Cringeley can figure a way for DynaCor to pocket a billion on the side, instead of increasing fuel efficiency in spaceflight? It'd happen next year.

• #### "net"? (Score:5, Insightful)

on Sunday November 15, 2009 @11:31AM (#30106230) Journal
Perhaps Cringely doesn't have a clear idea what sort of debris we are dealing with here

There are, certainly, some big chunks out there; but unpleasant enough(and far more numerous) are the little flecks of paint, bolts, and general fragments of this and that zipping around at bulletesque velocities.

Either this "net" will be made of very close-woven unobtanium, of the sort that we don't yet have, despite decades of interest in the personnel armor industry, or it will have to be a vast spongy particle trap, of the sort whose volume would be completely prohibitive for any available launch mechanism.
• #### Re:"net"? (Score:5, Insightful)

on Sunday November 15, 2009 @11:51AM (#30106410)
Not only that, but does he realize how LARGE that space is? Can you imagine saying to somebody, take your yacht, and sail around the oceans picking up 18000 pieces that go around with vastly different speeds (and orbits)? Now do this in 3D instead.

Moreover, the delta v's involved are probably quite a lot larger than one would expect.

And as you say, the big pieces are tracked and show up on radar, it is the little pieces that hit unexpectedly.

• #### Re: (Score:2)

And don't forget the \$200,000.00 ( USD ) bag of tools floating about, NASA ( one employee in particular ) would like to have it back!.

• #### Re:"net"? (Score:5, Interesting)

on Sunday November 15, 2009 @11:52AM (#30106418) Homepage

As long as you're traveling at the same speed and direction as the bulletlike flecks, you don't have to worry about damage. Given that space is a frictionless environment, it's actually fairly easy to accomplish this. We do it every time we dock with the ISS.

Cringley seems to be suggesting traveling slightly slower, as to absorb some kinetic energy in the impact, while preserving the integrity of the net. This sounds pretty cool in theory, although there are a few problems in practice, such as tracking all the tiny bits of debris, having enough fuel to maneuver, and ensuring that you don't get caught between two pieces of junk traveling in opposite directions.

It's a difficult problem to be sure, but I wouldn't write it off entirely.

As an alternate proposal, would it make sense to put huge blocks of aerogel (or a similar substance) into orbit? Junk that strikes the blocks would either get caught inside, or pass straight through (but lose some kinetic energy in the process, leading to its gradual orbital decay or capture). Aerogel itself has a low enough density that loose chunks of it would be relatively harmless to passing spacecraft.

• #### EXACTLY (Score:2)

Slowing or absorbing into something that itself is not that harmful is a much better idea! Aerogel is a brilliant idea!

I was thinking more along the lines of some sort of gun shooting bullets of something harmless... aerogel would be perfect. similar complex issue of proper aiming and avoiding using up all the fuel.

Another idea would be to use some sort of ION drive or something to try to stay in orbit; power source would be a problem and I'm not sure there are enough ions out there to do enough to count

• #### Re: (Score:2)

"As long as you're traveling at the same speed and direction as the bulletlike flecks, you don't have to worry about damage"

That's not true. Consider two objects in the same circular orbit traveling in opposite directions exactly 180 degrees apart. They are traveling in the same speed and direction (in physics that's called velocity) and will surely collide.

• #### Re: (Score:2)

Nate, read the text you quoted again. How does one travel in the opposite direction and the same direction at the same time?

• #### Re: (Score:2)

By same orbit I meant that their angular momenta would have opposite signs.

Think of the two objects, satellites, having telescopes that point straight ahead, that is, the line of sight is tangent to the orbit, and they both are focused on some distant star and are moving toward that star at that instant. At that instant they have the same velocity.

• #### Re: (Score:2)

while your statement is true, its also mildly retarded. yes, 2 objects on the opposite sides of a circle, traveling in opposite directions around the circle, for a short moment are traveling the same direction relative to one another, *but thats not what we're talking about here* we're talking about 2 objects traveling the same direction around the orbit.

your argument, while a marvelous display of spatial relationships, is pointless in relation to the actual proposal at hand.
• #### Re:"net"? (Score:4, Informative)

on Sunday November 15, 2009 @03:38PM (#30108612)
4/3 * PI * R^3

Re = 6,378 km

Low earth orbit starts at ~200km:
Rleo1 = Re + 200km = 6,578km

Low earth orbit extends up to about 2000km ( it's debated. Using nice round numbers )
Rleo2 = Re + 2000km = 8,378km

4/3* PI * ( Rleo2^3 - Rleo1^3 ) = 1.271E12km^3

1.3 trillion cubic kilometers of space to sweep.

Assume a block of aerogel 10 meters on a side - so a frontal area of 100 m^2. That's pretty big, and it won't get any bigger unless we figure out how to manufacture the gel in space:
Agel = 100m^2
= 0.0001km^2

Velocity in leo is around 7.5km/second, relative to the ground.
Vgel = 7.5km/s

Let's assume that we are just trying to sweep the entire volume of space once, ignoring that things are moving etc. Even one sweep of the volume would certainly clean up a lot, if the orbit of the gel is tangent to the orbit of most of the junk. So we just pretend that the block of gel is flying down a tunnel, basically - frontal area times velocity * time equals volume cleaned:

Vclean = Agel * Vgel
1.27E12km^3 = .0001km^2 * 7.5km/s * t(s)

t = 1.695E15 seconds
= 5.37018E7 years

= 53 million years.
• #### Every velocity is super-bulletesque (Score:2)

Every velocity in space in orbit is super-bulletesque. It's the relative velocities that matter. I could catch the paint fleks with any old material, if, the relative velocities were reasonably close. Indeed, if you launched me out of a cannon next to a bullet fired out of a rifle, I'd almost be able to catch the bullet with no harm to myself. It's just the launching and the landing that would suck.

• #### Re: (Score:2)

Perhaps Cringely doesn't have a clear idea what sort of debris we are dealing with here

He probably doesn't, but that's never stopped him opening his mouth before.
• #### Can you Catch a Cannonball in a Fishing Net? (Score:3)

Perhaps Cringely doesn't have a clear idea what sort of debris we are dealing with here.

No, he doesn't seem to have a clear idea of what debris is, or what orbital energy is, or how orbits work, or how BIG space is.

It is reasonable to clear debris up from Earth orbit... but not the way he proposes.

I'm afraid I have to agree with the people saying that this is not a workable idea. He needs to put some numbers to it. He's going to catch basketball sized objects in a net? Have he thought about what happens when a massive object hits something at several miles per second? I'd say, picture tr

• #### Re:"net"? (Score:4, Funny)

on Sunday November 15, 2009 @03:04PM (#30108270)
I would think that if we went 'spongy', it would make sense to send up a few cubic meters of a densely packed raw material and then extrude it in space; after all, the whole point of those materials is how low density they are. One jar of popcorn kernels is easier to transport before they're popped.

Do popcorn kernels pop when exposed to vacuum? I may have solved the issue, right there.
• #### Quark! (Score:2, Interesting)

by Anonymous Coward

Anyone remember Quark, a space garbage scow show from the 70's? :D
It's nice to see it's time...

• #### Re: (Score:2)

Anyone remember Quark, a space garbage scow show from the 70's? :D It's nice to see it's time...

That was exactly what I thought of when I saw this .. ah the memories of seeing it on TV and the crushing blow when it was discontinued.

• #### Re: (Score:2)

QUARK! GARBAGE! Having Betty I and Betty II around made up for it...
• #### you are the clone. no, you are the clone. (Score:2)

Anyone remember Quark, a space garbage scow show from the 70's? :D It's nice to see it's time...

Quark [imdb.com] was the first thing I thought of when I saw the heading. Life imitating art.

• #### Re: (Score:2)

Anyone remember Quark, a space garbage scow show from the 70's? :D

We should re-task the Enterprise... it's nothing but a garbage scow anyway.

• #### Re: (Score:2)

Actually, Korax clarified his statement to say that he didn't mean to say that the Enterprise should be hauling garbage, but that it should be hauled away as garbage.
• #### Space junk's like any other problem (Score:2)

Until something tragic happens because of a piece of space junk, no one will do anything.
• #### Re: (Score:2)

While there have been no 'tragic' accidents, there certainly have been dozens of satellites knocked offline due to collision with debris.
• #### Metal (Score:3, Interesting)

on Sunday November 15, 2009 @11:47AM (#30106376)
Wouldn't something like a big ass electromagnet be useful? I mean, compared to a net... or something along the lines of giant flashlight (to push crap into earth)
• #### Re: (Score:2)

The real trick is a)space saving [magnets are/can be very heavy] and b)What about non-magnetic things? There are plenty of those up in space, so dealing with them is important as well.
• #### Interesting idea (Score:2)

But I think that I would prefer a set of these, and dispense of them after a shorter time (burn it up or capture it for material studies). For starters, imagine accumulating a bunch of that junk together and then losing the ship. It could actually make things worst.

Also, this would be a good use for the tug concept. At some point, a tug will be useful for space. This could help push the concept.
• #### Use Aerogels to slow objects w/o fragmentation (Score:5, Interesting)

on Sunday November 15, 2009 @11:50AM (#30106402) Journal

IF (and I know it is a big IF) it were possible to "manufacture" aerogels in space, this material could be ideal for capturing/de-orbiting small pieces of debris that would be too difficult/expensive to chase and capture the traditional way (via space tug or whatnot) but still poses a threat. Aerogels have already proven themselves as capable of capturing extremely fast (although tiny) particles moving at literally astronomical speeds without itself disintegrating. It was used precisely for this reason in both the "Stardust" and "Genesis" probes.

Now imagine instead of the small plates that were on these probes a very large slab tens or hundreds (thousands?) of meters on a side that would, over time, slowly intercept the smaller particles. Larger fragments would still go right through but might lose enough kinetic energy (without fragmenting and making the problem worse) so as to de-orbit themselves. The only thing that might make this remotely possible is the thought that the aerogel is so light (lighter than air) that a really huge piece could be put into orbit without spending billions in launch something heavy. Of course the only way to keep the launch volume reasonable is to MAKE it in space. Once in space, an ion engine would be required to counteract the atmospheric drag (and loss of kinetic energy from the impacts of the space debris).

By "manufacture" I mean the raw material (I guess it some sort of silicate compound) would have to be brought up from earth but since the resulting aerogel is 99.9% empty space, a little could go a long way. I understand that one way to produce it requires a super-critical liquid carbon-dioxide solution; obviously the CO2 would have to be recycled or better yet would be if a means of producing it directly in vacuum. Chemists, any ideas?

• #### Re: (Score:2)

Aerogel is pretty brittle, though. One can imagine flaking as a result of impact and no real net benefit debris-wise. I think something ductile would be a better choice. Like, say, steel foil, perhaps.

You want every impact to slow down the object enough that de-orbit occurs within months instead of years, and any detached pieces of the cloak should also have a similar profile. Only the intact cloak itself should be able to orbit for a time, until it is decided to de-orbit it, as well.

• #### Re: (Score:2)

Didn't know that about Aerogels. How about wrapping the whole thing in a (very) thin layer of "saran" wrap? (to non-Americans that's transparent plastic wrap). It'll keep the whole thing from fragmenting without (hopefully) adding too much to the weight.

Also, I'm hoping that little pieces of the Aerogel will be relatively "harmless" upon impact (is anything harmless at 25,000 mph)? Perhaps the "wrap" could be made non-transparent to something like UV while the Aerogel could be tailored to disintegrate up

• #### Re: (Score:2)

I don't believe an ion engine would be enough to keep anything stable that close to any planet. Their thrust is so low it would be like peeing in the ocean.

• #### Re: (Score:2)

I think the idea would be to put this Aerogel barge in a pretty high orbit. Anything in low orbit would naturally come down in a reasonably short time because of atmospheric drag.

• #### Net? Use massive slabs of Aerogel instead (Score:2)

And by massive I mean square kilometres and tens of meters thick.

Aerogel [wikipedia.org] has been shown to be able to pick up even the smallest flecks of material for the Stardust [wikipedia.org] project.

Since it's the smallest things that are the trickiest (huge bits are easily tracked), we need something that will not only absorb the energy of the impact, but also keep the debris in place. Thus, Aerogel is a good fit.

• #### Gel or Foam? (Score:2)

What about some gel block, or even better some kind of foam?

• #### One other thing (Score:2)

It makes sense to capture and lose the small pieces. BUT, the large ones are lots of material in space that took a lot of fuel to get there. That would be a shame to lose those if they are together. Seems like we can push those into a higher orbit out of the way and then use them in the future.
• #### Conservation of energy/momentum (Score:2)

...means the net will lose speed every time it captures some junk. The author needs to take high school physics again.

Tacking on a sailboat works because the wind is blowing on the sail, adding energy to the whole craft.

Scooping stuff in a net is just an inelastic collision. The momentum gain of the junk will equal the momentum loss of the net. The net's orbit will decay as it captures more and more junk.

• #### Re:Conservation of energy/momentum (Score:4, Informative)

on Sunday November 15, 2009 @12:22PM (#30106664) Journal
It's not quite that simple. If the orbit is elliptical then two orbits can intercept even though they have different energy level (average heights). If the two objects in the two orbits join then the one in the higher orbit will lose energy and the one in the lower orbit will gain energy (which corresponds to average height). The resulting object will have the same momentum as the vector sum of the momentum of the two objects, which will give it a new orbit. If you start in a low and highly eccentric orbit, after a number of such collisions you may end up in high and relatively circular orbit (or not, depending on the collisions). Cringely is broadly right that it is probably possible to design an orbit such that the net eventually collects everything. Unfortunately, 'eventually' in this case can mean several million years, possibly longer.
• #### Re: (Score:2)

...means the net will lose speed every time it captures some junk. The author needs to take high school physics again.

You might want to consider a good orbital mechanics course yourself. If, as an example, I am travelling in an elliptical orbit with apogee at, say, 500 km and perigee at 300km altitude, and I hit a bolt in a circular orbit at 500 km, then I have just run into something that is going FASTER than me.

Which means that I'll speed up slightly, raising the perigee of my orbit.

The assumption that

• #### Speed of debris is 25,000 ft per second. (Score:2)

Particles the size of a grain of sand - assume 1 gram. Speed: 8333 metres per second. Kinetic Energy Formula: 0.5 * mass * velocity * velocity.

Kinetic Energy of grain of sand: 34,719 joules.

Small car travelling at 30mph, mass 1000kg. Speed: 13 metres per second.

Kinetic Energy of car: 84,500 joules.

Area to which impact of grain of sand occurs: assume 1mm square.

Kinetic Energy per square metre when grain impacts: 34 billion Joules/Sqm.

Area to which impact of car occurs at 30mph: assume 1 sq m.

Kinetic Energ

• #### Re: (Score:2)

You don't need to hit it head-on, and you don't need to bleed all of the orbital energy to put the debris chunk into a rapidly decaying orbit.

Presuming that there is only a countable number of objects (a few thousand, tens of thousand, even a million), it's much more reasonable to approach "just enough" to knock them into a month-long freefall instead of a decades long, one at a time. A computational nightmare, perhaps, and definitely extremely tricky to line up the right piece of debris without putting yo

• #### Gain kinetic energy? (Score:3, Interesting)

on Sunday November 15, 2009 @12:12PM (#30106580)

To drop from a higher altitude to a lower altitude you have to lose kinetic energy, not gain it. Furthermore, everything is not traveling in the same direction. There are many different orbits and junk is in all sorts of them. So some junk you'll never "net" since it's traveling in the same direction as the dejunker, and other junk is traveling exactly opposite and will slam into the net with twice the velocity of the denetter's current orbital velocity. Furthermore if the junk's orbit is 90 degrees to the dejunker, it will never be caught either. Even if the orbital paths crossed, it would probably just destroy or damage the dejunker satellite (paint fleck or rachet wrench).

So it wouldn't seem that his idea stands the common sense test (or physics for that matter). But this is just slashdot and I am not an orbital-mechanics expert. I failed that class at the starfleet academy (or was that temporal mechanics).

• #### Re: (Score:2)

Orbits are a combination of potential and kinetic energy. Depending on what orbit you are in, and what phase of the orbit you are in at the time those numbers will flip around being the predominant one.

So, depending on what you are doing, where you are now, and where you want to go you may have to do some counter-intuitive moves.

• #### Danger! Danger! (Score:2)

Unfortunately, the operation of a space garbage scow is fraught with danger [youtube.com].

• #### Quark (Score:2)

Need i say more?

• #### Good way to use Bigelow (Score:2)

Bigelow has a small line to build Kevlar material for their space stations. It is suppose to handle 17000 mph pieces. Seems to me that BA might want to get in on this if funds were to be done. At the very least, it helps gets their line started with building items.
• #### science fair-y tale (Score:2)

cringely sounds more and more like a clever junior high school student. nothing wrong with that, if you're in 8th grade. but i mean seriously, the volume of 3-d orbital space determines among other things the energy and time required to sweep it "clean." be almost faster just to wait for the junk to re-enter. cheaper and cleaner certainly.
• #### Why a net? There's no resistance in space! (Score:2)

Why a net? There's no resistance in space and no medium that needs to pass through the net! Make it a big metal cup like the back of a dump truck. Drawback would be increased payload for launch, but it helps remove a lot of the risks others are describing such as the net breaking or contents of the net breaking up into smaller pieces.
• #### Re: (Score:2)

because a net can fold up and fit inside a rocket capsule.

• #### Garbage scow? Nay, space sharks! (Score:2)

I say we launch sharks with frikkin' frakkin' lasers to vaporize the stuff. Who cares if they'd conserve energy and momentum, they're sharks and they fry things!

• #### Go back, start over. Way back. (Score:2)

He does need to apply a little math there. Dragging a net behind might happen due to (weak) atmospheric friction, but you're not going to sneak up behind debris and gently catch it in the net. Something in a lower orbit is moving faster relative to you, so the debris will come from 'behind'.

Also, you're going to be waving a huge net around and hope to only get close enough to things that are traveling at speeds which are only slightly different. Somehow you have to not catch working equipment, and not

• #### its the travelling salesman problem (Score:2)

with 18,000 destinations, all of them moving, and each with a different angle, trajectory, spin mass, etc...

http://en.wikipedia.org/wiki/Travelling_salesman_problem [wikipedia.org]

so while the idea as a real world solution is obviously impractical, its a great way to exercise computer scientist minds to dizzying distraction

• #### He doesn't understand orbital mechanics (Score:2)

"It won't always be possible, of course, to gain energy from each encounter, but that's why we start in a higher orbit, so as energy is inevitably lost it can be replenished by moving to a lower orbit."

Changing to a lower orbit will increase velocity, yes, so in a sense you're trading off potential and kinetic energy... but in the sense that matters... maintaining the ability to change your orbit... it doesn't matter if you go up or down, it matters only that you are changing your orbit. Any change in orbit

• #### A problem of scale... (Score:2)

Consider for a moment that the sphere of a high orbit is larger than the size of the earth. Then consider all the orbital altitudes (like layers of an onion) which need to be "scoured", and you're talking about an amount of space that is many times the total surface area of Earth.

That's a whole lot of territory to cover, even for a large army of scour-ers.

• #### My plan is better than Crigley's (Score:2)

I say we just send Superman up there with a big net and let him make a bunch of trips around the planet to clean everything up. Then we don't have to worry about conserving the energy in the pieces or any of that crap, because Superman has energy to spare.

Not only is this faster and safer, but much more entertaining. I think they could actually make a profit on this, when they figure in the comic book sales.

• #### Re: (Score:2)

he'd probably end up flying around the planet backwards to many times, and set us back to the stone age. there's a lot of debris up there.
• #### Tacking may not work in Space (Score:3, Insightful)

on Sunday November 15, 2009 @11:23PM (#30111928) Homepage

The notion of capturing energy from objects already in orbit is intriguing - but I doubt that "tacking" is sufficient to explain how this works. Tacking occurs when two fluids are connected by airfoils; moreover, the essence of tacking requires the deflection, or bouncing, of the fluids - not the collection of same.

So, in what way could you approach an object and steal its energy. But before that question, what does it mean to steal energy from these captured items? If the trash ends up a part of the garbage scow's orbital dynamics, then "stealing" energy is moot - unless the trash is ejected into a less energetic orbit, the scow cannot end up with a more energetic orbit - which of course defined the solution. The desired "net" may be an electromagnet on a long wire. The intercept is made with a near miss, such that trash and the scow end up like a double-star, tumbling around a common axis - then the electromagnet is released in a moment when the trash is tumbling counter-orbital, leaving the trash in an inferior (and hopefully terminal) orbit - and the scow in a new trajectory of choice - based largely on the intercept angle (to establish the tumble plane) and the release timing to select the angular acceleration.

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