Could we clean up space junk like this?

For a while now I’ve been concerned about orbital debris, AKA space debris, AKA space junk. I’ve read about proposals to use lasers and water cannons to try to force this junk out of orbit, but I’ve had an idea, and I’m wondering how realistic my idea is.

My idea is to create a “cloud” of air in orbit, and any debris passing through it would be slowed down, so as to fall out of orbit faster. The cloud would be created by a rocket that had tanks filled with compressed air, or more likely tanks of liquid nitrogen and liquid oxygen in a roughly 3:1 ratio.

Could such a scheme actually work? Would it make a difference? I’m guessing that my “air cloud” would dissapate fairly quickly, which is probably what you’d want, so that satellites or the ISS aren’t jeopardized. Could there be any effects on the weather by adding a pocket of extra gas up there?

I suspect you’d need a lot more gas than you can provide – it’ll disperse pretty rapidly, and as it does so its ability to slow things down will rapidly decline. The gas will then either pick up energy and move out of the orbit or, more likely, lose energy via collisions and fall back into the atmosphere. After all, if it were energetically possible for a lot of gas to be there, it would probably already be there.
The idea of retarding the motion of such orbital debris has, I know, been advanced, but in a much more targeted way. I know that people have suggested using laser propulsion to do it. I’ve actually worked on laser propulsion, and I do think this would work – you can get an impressive jolt from a short intense laser beam, and it will send light objects moving (or, alternatively, really decelerate them). We blew dime-sized pieces of plastic across the room. And laser work really well in space, whgere there’s nothing to absorb the light, scatter it, or change refractive index and cause “thermal blooming”. The problem would be building the complex, self-controlling system to maneuver close enough to targets, to aim at them, fire, and adjust as necessary.

How large of a cloud are you thinking? How dense will it be, and how long will it last? How will you place it in the path of the debris you wish to slow down, and how long will that debris remain in the cloud?

What kind of cloud will it be? Water? Nitrogen? How will you get it there? How much will that cost? Who will pay for it?

Distances in space, even in orbit, are vast. Speeds are pretty damn fast (17,500 mph). Also note that there are already clouds at some altitudes that we think of as space. The International Space Station, at about 250-300 miles up, is slowly dragging on atomic oxygen (that’s single oxygen atoms, not O2 molecules).

Why bother?
It will all come down eventually, on its own, without us having to do anything. And it hardly ever hurts anyone when it comes down – usually burns up before reaching the ground (or sea, most often).

After we’ve dealt with the 1,000+ children starving to death every hour, and deal with some of the epidemic diseases, etc., we can invest some money in your scheme for solving this problem that worries you so.

[Moderator note]

Remarks like this really aren’t appropriate for GQ. No warning issued, but let’s refrain from such comments in the future.

General Questions Moderator

As you probably know, the earth’s atmosphere expands and contracts with the sunspot cycle, and theexpansion does increase the rate at which satellite orbits decay

I expect it’d take more atmosphere than anyone would feel comfortable giving up to get an effect larger than that caused by the sun itself. Still, I suppose we could rig something with giant space mirrors converting sunlight to nitrogen heating microwave frequencies (if there is such a thing) and bake the exosphere up even higher than usual.
That sounds pretty expensive.

It seems as if the effect would be the same on junk as on operational satellites: either not much (in which case why bother) or significant (in which case some useful space systems are jeopardized).

Beside all of the problems already mentioned, space debris is intermingled with operational satellites. Even if it were possible to slow down everything within a certain region, you’d end up slowing down things that we don’t want to deorbit.

Also space is very, very big. You’d need a cloud miles long/wide/high if you want any significant chance of it actually impacting anything. If you want it to do any good, the cloud would have to have some density to it. Launching the amount of matter to create an enormous, relatively dense cloud would be prohibitively expensive. Plus it would dissipate/reenter quickly.

It will take decades for the debris to re-enter on its own, and in the meantime it poses a non-trivial threat to both unmanned and manned craft in Earth orbit.

It’s not a MASSIVE problem, but it is a REAL problem, not some silly made-up sci-fi threat.

Water cannons? In space?! :dubious:

** ** said:

The concern is not what it does when it comes down, it is the hazard it represents to spacecraft. A tiny bolt could puncture a hole in the International Space Station, or put a hole in a communication satellite’s fuel tank, or make a spy satellite blind just when you need to snap pics of some potential terrorist training camp. Space debris is a real threat, and can hang around for years if not decades.

Xema said:

I read the OP as intending some sort of localized cloud effect, such that you disperse it in the vicinity of the space junk, it slows said junk, then dissipates so it does not affect anything else. That would require not only tracking the junk (which we do for things larger than 2 in), but timing a “cloud delivery satellite” to a rendezvous to deliver the cloud. Seems overly grand in scale to accomplish very little in results. A separate satellite for each piece of debris? How many iterations does it take to significantly alter the course of the debris?