Elon got his rocket up ...

[DeltaV]

Space junk becomes a problem. If you have people putting up lots of cheap stuff that breaks down the whole time, you get to the point where you'll lose track of it, and where it interferes with most launch trajectories. There's also the danger of two large satellites colliding and turning into a cloud of thousands of bits of shrapnel, some of which can then cause other spacecraft to disintegrate, magnifying the problem. Some people I've talked to who've had jobs involving tracking objects in orbit etc. think that there's already a dangerous amount of junk up there.

Some fear an orbital debris chain reaction (sort of like fission).
http://www.denverpost.com/headlines/ci_5165772

[Skipjack]

Space junk becomes a problem. If you have people putting up lots of cheap stuff that breaks down the whole time, you get to the point where you'll lose track of it, and where it interferes with most launch trajectories.

I agree that space junk is a serious problem already.
Most of that junk is from spacecraft that were built in times when nobody cared about the possibility of space junk. I think there should be a law though (if there isnt already) that all new sat need to have the ability to deorbit themselves.
For all the others, there is a business oportunity for someone and this will again mean more launches.

[GIThruster]

Here's an interesting idea some folks are working on:

http://www.engadget.com/2010/03/29/cube ... eep-atmos/

though, IIRC, it takes less energy to lift from the various GEO orbits and dump into the Sun than to crash something back to Earth. If that's true, one wonders how well researched this idea is. In any case, 22k miles is a high orbit so if one wants to do something other than park them in the graveyard, it may well be better to loose them at the Sun than to crash them, especially when there's still hydrazine aboard (which I believe is the rationale for shooting them down.)

[zapkitty]

Some fear an orbital debris chain reaction (sort of like fission).
http://www.denverpost.com/headlines/ci_5165772

Actually, a Kessler cascade is happening even as we type at each other.

Kessler Syndrome does not necessarily posit a single collision that initiates a chain reaction that renders LEO uninhabitable...

... although that technothriller macguffin was and is a real possibility and a steadily growing one at that...

... Kessler was describing a syndrome where collisions among debris would generate sufficient additional debris to exceed the risk from natural micrometeorite strikes.

As I said in another thread we're long past that point. By the time sufficient data could be gathered to test Kessler's hypothesis OD had already outstripped MM as the leading cause of spacecraft strikes.

And it's making itself worse every day.

Kessler Syndrome? You're soaking in it!

[kunkmiester]

I was thinking a non-profit would eventually be organized to provide general cleaning and deorbiting of stuff no one's responsible for/can't afford to do. This would include deorbiting big things, and large diameter aerogel disks to "plow" large clouds to absorb small stuff and then remove it from orbit.

On the other hand, with launches cheap enough, a company looking to launch might actually pay for a few extra to lift the sweepers and tugs to clean out their intended orbit.

[93143]

how cheap would it have to be to get people signing up?

I do not really think that there is some kind of sweet spot. With every dollar that the pound gets cheaper a couple of more potential clients have space within the reach of their budgets.

http://www.spacefuture.com/archive/desi ... kets.shtml

The first graph under "RLV Requirements Summary for Future Markets" is rather dramatic...

[pfrit]

I was thinking a non-profit would eventually be organized to provide general cleaning and deorbiting of stuff no one's responsible for/can't afford to do. This would include deorbiting big things, and large diameter aerogel disks to "plow" large clouds to absorb small stuff and then remove it from orbit.

On the other hand, with launches cheap enough, a company looking to launch might actually pay for a few extra to lift the sweepers and tugs to clean out their intended orbit.

Actually, most LEO space junk is small. That doesn't make it safe, but it would allow for a very cheap way to deorbit space junk easily. Put a laser satellite in LEO and use a phase conjugate targeting system to identify all particles that are moving towards it at any time. Fire on them to decelerate them. Most LEO space junk is things like nuts and washers. You wouldn't need to put much energy into them to knock them out of orbit. Cheap and easy and wouldn't weigh much.

[zapkitty]

Rearranged the order of your statements a bit...

Actually, most LEO space junk is small.

Quite true... but this part...

Most LEO space junk is things like nuts and washers.

... not quite. Most OD is smaller than 1mm in diameter and consists of solidified metal droplets from explosions and solid rocket motor exhaust, paint flakes, corrosion flakes, the remaining non-metal solid rocket motor propellant particles... that's the scale of the most common objects in LEO.

And yet they still punch holes in spacecraft.

... and so your solution...

That doesn't make it safe, but it would allow for a very cheap way to deorbit space junk easily. Put a laser satellite in LEO and use a phase conjugate targeting system to identify all particles that are moving towards it at any time. Fire on them to decelerate them.

... and...

You wouldn't need to put much energy into them to knock them out of orbit. Cheap and easy and wouldn't weigh much.

... would require detection gear with a resolution at range that far outstrips anything ever placed in orbit.

Is it possible?
Of course.

Is it the most efficient method?
Unknown

[Skipjack]

I know that a large part of the space junk in orbit is very small. This space junk will be very hard to remove.
I have thought about that a lot. My take on it is that any improvement is an improvement though. So deorbiting the large stuff will at least help a bit. It will also help avoid getting more small debries from collisions caused by the larger junk.
So in any case, it is worth doing, if we can get the launch costs down enough for this to be feasible.
I am not sure what the ideal technique looks like to do all that either.
I suppose that it would be enough to just slow the stuff (be it small or large) down enough for the orbit to degenerate so that it will burn up in the atmosphere. You have to be more careful with larger junk that wont burn up completely, so it wont come down over inhabitated areas.
I think that zapping smaller junk with a laser to slow it down is a good idea.
In any case, anything helps!

[KitemanSA]

There seems to be a confusion about two different topics, LEO space junk and GEO orbital slot exhaustion.

Certainly a solar sail might be the best way to clear GEO slots, and using one to boost satellites out of EO at all may be the bestest cheapest way... and reusable too. But a solar sail in LEO is just plain nuts. Ok, I'll admit that there MAY be a chain of logic that uses them to remove the larger junk to prevent generation of smaller junk, but there are easier ways.

One HIGH tech way was stated earlier, the LASER shooter-downer. A lower tech cheaper way is to tie a conductive string to one and let the interaction with the earth's magnetic field drag it down. Indeed, EVERY item sent up should be required to have a de-orbit function built in. Two, spring-loaded electro-dynamic tethers (conductive strings) that pop out at the end-of-life; and bang-zip, the item is out of the LEO skies! Check out Tethers Unlimited for these items . http://www.tethers.com/

For the micro-junk, the paint flakes etc., I kind of favor the aero-gel route myself.

[Skipjack]

For the micro-junk, the paint flakes etc., I kind of favor the aero-gel route myself.

Would aerogel really work? I know it worked for the stardust mission, but there it was not really meant to slow fast moving particles down, was it?
I was thinking more along the lines of a large blanket of carbon nanotube fabric (not available yet) to make some sort of giant cosmic snow plow.
Now there are two issues that I see with this technique:
1. Even with a huge blanket, it would take forever to clear even a fraction of LEO. I mean there is "a lot of space in space", even in LEO.
One could maybe clear some defined orbits, like streets. You would probably still have debris coming in from other orbits though.
2. The blanket would probably work like a solar sail and even worse, it would probably interact with the atmosphere, so it would need a lot of boosting, or it will be very temporary.
I do fully agree that anything placed in orbit should be required to have some way of deorbiting it again...

[GIThruster]

IIRC, everything in LEO picks up charge. Could be you might make an electrostatic sweeper for small particles and at least avoid having to "brush" every square inch you want cleaned.

[Tom Ligon]

GIT, reviewing the posts above I was thinking just that.

An aerogel pillow would pick up the good with the bad.

I expect most objects in space develop a surface charge. The smaller they are, the higher the charge to mass ratio is likely to be. (This should scale with surface area to volume). Thus, little stuff should be easier to handle with electrostatic or magnetic sweepers of some sort.

I wonder if the first Bussard Ramjets will actually be trash sweepers?

[KitemanSA]

An aerogel pillow would pick up the good with the bad.

IMHO, anything big enough to be "good" will be avoidable by the chip-swatter.

My "chip swatter" design. Two aerogel (or other material with such intent) targets at the ends of a pair of fairly long tethers such that they can be lifted and lowered as needed to avoid "good" stuff and allow the captured material to be dropped at <orbital velocity into the atmosphere.

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Maybe the upper one needs to be aerogel to capture the items while the lower just need to present a momentum absorber sufficient to de-orbit the particle. After all, in this design, the lower target is going MUCH slower than orbital velocity.

[zapkitty]

One could maybe clear some defined orbits, like streets. You would probably still have debris coming in from other orbits though.

In fact that's the primary collision geometry.

But even a "glancing" blow takes place at orbital velocities... so imagining them as if they were like cars in merging lanes colliding must take into account the fact that these "cars" are not attempting to match speeds and directions and are each going in excess of 17000 miles per hour in their own particular lane... with a velocity difference most often measured in km/s

Now imagine that in 3D

But debris from a satellite or launch need not stay in the same orbital track as the parent body. Depending on the mechanism of separation from the parent body it drifts outward or flies outward or sprays outward on a path of its own.

And so debris from from low inclination orbits, debris from mid inclination orbits, debris from high inclination orbits, debris from polar orbits, and debris from actual retrograde orbits* all make an inescapable net.

And now imagine that in 3D

*Retrograde is most often sun-synchronous sats which are a bit retrograde or Israeli spysats which just plain orbit the wrong way.