A few tons of very cold gas is placed in an orbit around the Earth traveling in the opposite direction to the trash. The gas would very quickly dissipate to the point where it is barely detectable. Nevertheless, for a time, I don't know how long, the gas molecules will continue in orbit and will impact with trash they encounter slowing it and causing it to drop into a lower orbit. Over time this process could help deorbit the trash. This gas would have the greatest effect on smaller and lighter trash because such objects have a relatively small amount of mass for their surface area as compared with larger objects. Something as large as a Space Shuttle would easily compensate for any slowing due to this very diffuse orbiting gas. This orbiting gas measure could be thought of as temporarily putting orbiting space trash into a very low orbit.
-- hangingchad, Nov 28 2004

Space Debris Update http://www.windows....pdate.html&edu=high
Several articles on space trash [hangingchad, Dec 04 2004]

Planetes http://animenfo.com...qkfo,planet_es.html
An anime series that uses orbital garbage collection as a premise [5th Earth, Dec 05 2004]

Launch Speeds and Earth Rotation http://www.aerospac...ecraft/q0115b.shtml
Explains acceleration needed for east-to-west orbit [hangingchad, Dec 07 2004]

Similar Orbital_20Garbage_20Snooker
but has the extra advantage of salvageability [FlyingToaster, Feb 13 2009]

Another variation on the theme Vacuum_20Cleaner
Orbital velocity, of the stuff we put in the way of space junk, is not needed. [Vernon, Feb 14 2009]

Boeing proposes using gas clouds to bring down orbital debris http://www.gizmag.c...allistic-gas/24403/
Little, temporary clouds. Follow the source links at the bottom of the article. [baconbrain, Oct 09 2012]

What happens to the delivery vehicle? Creating space trash to clean up space trash?
-- ConsulFlaminicus, Nov 28 2004


[ConsulFlaminicus] Upon reaching orbital speed the last stage could pump out the liquified gas or release granular or powdered frozen gas into orbit. The last stage would then deorbit by firing a rocket to slow down and reenter the atmosphere.
-- hangingchad, Nov 28 2004


1: Create delivery vehicle largely out of dry ice. The vehicle itself will emit the gas and disappear when it is done.

I have seen a similar idea using sand or scrap metal as an antisatellite/ antispace trash action. The problem would be that orbit would be rendered unusable forever for anyone: sort of a scorched earth procedure. But the sort of thing that might be useful for a nation like North Korea in a fight against the US. The use of gas for this would be less efficient but reversible, and so I give bread.
-- bungston, Dec 05 2004


What about the debris travelling at roughly the same velocity as the gas? Why would the gas stay in orbit when our atmosphere is incapable of doing that same at that distance?
-- wagster, Dec 05 2004


[wagster] There should be very little debris travelling at the same velocity (and direction) as the gas. The proposal is to place the gas into an East to West orbit. Most satellites (and debris) are in a West to East orbit direction (launching eastward takes advantage of the speed due to the spin of the Earth). Therefore, the gas would strike debris at roughly twice orbital speed.

The gas would be in orbit and that is why it would remain (for awhile) at low earth orbit distance from the surface of the Earth. Our atmosphere is almost entirely missing at this distance because it is not at orbital speed (and direction) and because the Earths gravity moves gas molecules not "bouncing" off other molecules toward the center of the Earth. Continual attraction and random "bouncing" results in half of our atmosphere below 5.6 km (18,500 ft) and almost nothing at 161 km (100 mi).
-- hangingchad, Dec 05 2004


[hangingchad] - Both answers seem to hold water to me. I am still a little concerned about the sheer amount of gas you would need, but this might well work. Could I suggest that given current concerns about our climate, CO2 would not be the ideal choice - N perhaps? (Or NO2 for comic effect).
-- wagster, Dec 06 2004


This "cleansing wind" would be compensatable by the space station perhaps, but not by many satellites. Most don't have the energy reserves needed to continually adjust their orbits in the face of this wind, and this would impact their accuracy.

Wouldn't this also interfere with land-based telescopes?

And, of course wayyyyy too much mass would be needed. The costs would be literally astronomical.

But you still get my croissant for being interesting :)
-- sophocles, Dec 06 2004


The cost of putting something in a west-to-east orbit is fairly high. Putting something in a polar orbit is extremely expensive. Putting something in an east-to-west orbit requires an effort similar to putting something on the moon.

With what it takes to put something in an orbit like that, you'll create more orbital debris than you could possibly bring down. You said it yourself, the gas would quickly dissipate. It wouldn't be there long enough to stop an orbiting grain of sand, much less a significant chunk of debris.
-- Freefall, Dec 06 2004


[Freefall] see new link The extra acceleration needed to put something in east-to-west orbit is nowhere like that needed for a Moon mission. From Cape Kennedy an extra acceleration of 2,945 km/hr (1,830 mph) would be required above the 28,886 km/hr (16,085 mph) acceleration for an eastward orbit -- not so significant. In contrast, to go to the Moon an extra acceleration of 11,256 km/hr (7,000 mph) was required.

With care I don't see why we couln't manage to put this gas into orbit without adding more junk. We would want to do this with care because any sizeable trash in a east-to-west orbit would be very dangerous to anything in a normal (eastward) orbit.

The gas would dissipate. I don't know how fast it would dissipate. I don't know how long it would stay in orbit. If the gas were very cold its expansion in a virtual vacuum would be rather slow. Where the gas goes once placed in orbit should be calculatable. A fairly simple experiment performed from the shuttle in a normal orbit should answer these questions. I just don't know. It's halfbaked.
-- hangingchad, Dec 07 2004


Well put - you done good. I'm with [sophocles] here - you'll just need too much gas, but it's still a good halfbaked solution. Have a bun.
-- wagster, Dec 07 2004


I was about to submit a similar idea when I saw yours, which is probably better. Mine was to orbit small dirty snowballs, either mostly of water or carbon dioxide, which would then collide with space debris, the resulting collision bringing both to sub-orbital velocity. Eventually the snowballs would dissipate under solar radiation if they didn't collide with anything. But you're probably right, it's better to start directly with gas, which could still provide enough gradual friction than snowballs and actually spread around a lot more. With this week's satellite collision we need ideas like this more than ever.
-- scottinmn, Feb 13 2009


//Eventually the snowballs would dissipate under solar radiation //
But presumably, the off-gassing (sublimation...whatever) would introduce unpredictable thrust and hence meandering of the snowballs?
-- coprocephalous, Feb 13 2009


//...unpredictable thrust and meandering//

True. Of course gas would also spread around; and if you're trying to collect a bunch of stuff in various orbits, that may be ok, although not essential. The only advantage I can see with the snowballs is perhaps that they could be tracked individually and avoided by other spacecraft (with a very complex computer)--until they start dissipating, which actually would be very soon. So I think it's better to just start with gas.

OK, so now I'm going to get all geeky and try to work this out using physics. Suppose we're trying to clear a range of orbits across a height range of 100km. All orbits are either equatorial or cross the equator, so we can simplify things by having the gas in an equatorial orbit; obviously this will provide more braking for an equatorial satellite than one that only crosses it occasionally, but we'll deal w/ that complication later.

Assume the gas spreads out across a 100km x 100km cross section(up/down, north/south). The earth's circumference is 40,000km (here as elsewhere I'm simplifying considerably for convenience). The volume of this space is 4 x 10E20 m3.

Suppose we put a million tons of gas in east-west orbit, which we could do with 10 Saturn V's. Dividing this by the volume in question, we get a density of 2.5 x 10E-9 g/m3.

Now consider a piece of space debris roughly 1cm3, with a cross section of 1cm2; if it has the density of water (which even a metal piece might have if not completely solid), it weighs 1g. It has a relative velocity with respect to the gas of approximately 15km/s. It then passes through the space of the gas at a rate of 1.5m3/s.

Multiplying the rate at which it intersects the space occupied by the gas by the density thereof, we get almost 4 x 10E-9 g/s. There are about a million seconds in a year, so in a single year passing through that equatorial gas, that 1g debris will have hit .004 g of gas going the other way, with 1/250 its momentum. I think that a delta-V of even -50m/s may be enough to cause an LEO object to intersect the upper air, which is about 1/150 the debris' orbital speed. So maybe it would take two years? Perhaps more, as it wouldn't absorb 100% of the momentum difference.

Complicating factors: for non-equatorial debris, only a small fraction of the orbit will pass through the gas. The worst is a polar orbit, which passes through the gas during .5% of its orbit; this will take 200 times longer to de-orbit. Obviously 400 years is too long, so I think we need more gas to get it; but very few items are polar, so maybe that's OK.

Also, if a satellite is larger than supposed, its mass grows as the cube of its diameter, cross section only according to the square, so it hits more gas but is not slowed down as much. De-orbit time will increase proportionately to its diameter, so debris 1m across would take 100 times longer than something 1cm across. This may not be a problem though, because we could track objects that large individually by radar, and send up individual interception missiles for those, leaving the gas for the smaller stuff.

So unless I've made a calculation mistake somewhere (order of magnitude errors can mess you up fast in space, so please double check my work!), this looks feasible. Obviously one downside is that it clears a whole range of orbits at once, so if you have any satellites you want to save you need to move or replace them. But if that's feasible, then it looks like the gas can solve our problem in a reasonable time. Of course if we ever want to use those orbits again, we either need a way of cleaning up the gas, or a steady power source to keep the satellites in orbit against the friction, and shielding for vulnerable parts against the high-velocity molecules up there.
-- scottinmn, Feb 13 2009


//Suppose we put a million tons of gas in east-west orbit, which we could do with 10 Saturn V's//
And the payload of a Saturn V was...? (are we confusing "pounds" and "tons" here, perhaps?)
-- AbsintheWithoutLeave, Feb 13 2009


How about orbiting a really big magnet?
-- MaxwellBuchanan, Feb 13 2009


somewhere to toss all the CO2... hmm
-- FlyingToaster, Feb 14 2009


How about a (really) big LASER, or fleet of such, in LEO?

Not only could particles be pushed around with the beam (photon pressure / surface vapourization), but it would make a nice spotlight for actually finding clouds of fine orbital debris - otherwise invisisble to radar.

Of course, it would not be used to take out any friendlies...
-- TIB, Feb 15 2009


//...are we confusing "pounds" and "tons" here, perhaps?)//

Um, yeah; tons and kg, at least. I realized this over the weekend myself. So I'm off by three orders of magnitude, and this won't work unless we have a radically cheaper launch system.
-- scottinmn, Feb 16 2009


Did [scottinmn] just suggest manmade comets?
-- shapu, Feb 16 2009


//manmade comets?//

Hm, I guess that could be another benefit of my initial idea, they might look pretty up there as they radiate away.
-- scottinmn, Feb 26 2009


Somebody at Boeing has filed a patent for temporary gas clouds. I linked to the Gizmag article I saw it in first. Source links are at bottom.

I think that individual molecules of gas, which is what you'll have after a while, will get driven away from Earth entirely by the solar wind. Or maybe it's just that an individual molecule, bouncing around in the gas the way they do that makes pressure, exceeds escape velocity sometimes, and if it doesn't hit another molecule, it's gone. Or maybe both. I need to look it up. Either way, a gas cloud will go away after a while.
-- baconbrain, Oct 09 2012


Cool idea and even cooler to see someone in the real world considering it. My suggestion would be to launch satellites in the normal West to East containing pressurized gas which is vented East to West to provide some of the orbital thrust. [+]
-- AusCan531, Oct 09 2012


Instead of launching this stuff, how about catching a comet and steering it down to orbit? They are full of gas and water and stuff.
-- bungston, Oct 10 2012


LEO debris apparently range from the macro to the micro, having non-uniform orbits making for turning any proximate object into more junk. with estimates that there are thousands of tons of such LEO debris, a low-tech, bulk approach is indicated. a mass-driver could kick a CO2 snowball up to altitude with just sufficient hang time to intersect some predictable nuisance. smaller "snow" flakes could be dispersed with a reusable shell. hundreds of such could be kicked upstairs daily.
-- manwhojaped, Jun 14 2020


It occurs to me that this would lead to the requirement that most new spacecraft be streamlined. That would diminish the effect once it's time to de-orbit that generation. Obviously most satelites would be designed to self-align into the wind or to be as dense and aerodynamic as possible: spheres, teardrops, and footballs. The addition of a deployable sail for when it's time to de-orbit would eliminate the problem. Put it on a timer so even if the craft doesn't respond to commands from home the sail will deploy.
-- Voice, Jun 14 2020



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