Is Space Junk Still A Problem? 17
critic666 asks: "I've been doing some research on space junk (trash orbiting the Earth), but most of the discussion about it seems to come from 1996 - 98. The only recent thing I've seen about space junk is from an Aug 20, 2000 article on NASA creating a laser "broom" to cleanup this trash. Does anyone know if anything's really being done about space junk now, is it just kind of a static issue, or have we solved the problem?" Most of Earth's "artificial satellites", as I like to call them, have orbits that will eventually destabilize, so that they'll eventually burn up on re-entry, however, this doesn't mean that there isn't still quite a lot of junk up there. NASA maintains a database of most of the larger pieces and does track them via radar and the Johnson Space Center maintains their own page on the subject. You might want to check out the FAQ. Thoughts?
Re:Very much so! (Score:1)
Aside from the fact that "Iridium" has only one "r", another flaw in your argument is that the cost of this hypothetical chain reaction at the orbit the iridium satillites operate at is relatively low. It's not going to end space exploration or anything nearly so exciting. The satillites come down by themselves because they are being constantly dragged by the thin upper reaches of the atmosphere at that level, and the broken up pieces would come down faster, because they have a better mass to surface area ratio. And no, the collisions won't permanently kick junk up into the higher orbits -- something shot up to that height from the low earth height would be on a highly eliptical orbit that would dig even deeper into the atmosphere on the low end.
So save your alarmism for your NASA grant proposal. We don't have money give away so it's wasted here, pal. Feeling a little bored after the Y2k washout, eh ?
Interesting...Not (Score:1)
The only stuff that will stay in orbit for tens of thousands of years are the asteroids that we move nearby.
Re:Caveats. (Score:1)
good idea... maybe.... (Score:1)
Interesting... (Score:1)
Essentially, it will form a ring system around the Earth first, somewhat similar to Saturns ring system, but not as big, of course. This will take several tens of thousands of years, and will occurs as a result of collisions between the objects tending to give them all the same vectors, eventually.
After another few tens of thousands of years, the ring will congeal into a spherical object - essentially another moon.
So, I suppose if we are *very* patient, the problem will solve itself.
--
Clarity does not require the absence of impurities,
A Few Days Late (Score:2)
Re:Very much so! (Score:2)
Makes me wonder about the validity of the rest of the stuff you're spouting off about...
Re:Very much so! (Score:2)
Preview before submit is a good thing.
I meant to say taking out two well chosen satellites might leave us with less than an hour a day without decent coverage.
Is space junk still a problem? (Score:2)
Are y'all talking about that new Star Trek series?
Sorry, couldn't resist. Actually Voyager is probably pretty good now since nobody in my market carries it anymore so I haven't seen any of this final season, and I hope the on coming up is as good as the later DS9 episodes.
Meanwhile back in orbit, what about salvaging and recycling all that stuff *in space* since we've already expended energy putting it up there. Collect it and hold it until the technology is available to turn it into parts of a space station or something.
Space defense. (Score:2)
An interesting idea, but it probably wouldn't work.
Firstly, if you have enough debris in orbit to harm anything that simply passes through briefly, then you have enough debris that it will collide with itself quite often. These perturbations will cause a lot of it to fall back to Earth, and the rest of it to clump together into large masses, ending when collisions become infrequent again (making the shield useless).
Secondly, aliens would probably just drop rocks on us if they didn't like us
It would be very effective at killing our own satellites, though.
Re:Very much so! (Score:2)
If the bird isn't near Earth-Moon Lagrange points 1-5, it is not a stable orbit. Try a search for "Lagrange L5" or "Lagrange trojan points".
Deorbiting Tether (Score:2)
Re:Not so interesting. (Score:3)
It's years for the satellites, months for the junk. The drag on a satellite is essentially proportional to it's area, so the deceleration is basically proportional to it's area/mass ratio. In other words, the orbit of a 10 gram bolt can decay as much as 100 times faster than the orbit of a 10 ton satellite. Of course, the satellite isn't as dense as the bolt, is likely to have big drag-creating solar panels, etc... but there's still an order of magnitude difference there.
Go up a few hundred miles and the situation gets nastier; orbital velocities aren't that much lower, but the influence of air drag is greatly reduced.
There's the problem. Around LEO, every hundred miles you go up, the air density drops by a factor of ten. By the time you put it in GEO, that bolt is going to be in an orbit that will hang around for millenia, being perturbed by the tide, by sunlight, etc. On the other hand, it's only in LEO that you have to worry about junk from a polar orbit hitting an equatorial satellite at several kilometers/second relative velocity. Stuff around GEO is lower speed to begin with, and is pretty much restricted to the same plane and same velocity so relative impact speeds are reduced too.
Current material, useful FAQ for /. posters (Score:3)
Caveats. (Score:3)
Then, there's the danger of a chain reaction. One satellite or rocket fragmenting from a collision, generating enough debris that those fragments will, in turn, hit other objects, and so on.
This would only happen if a very large chunk struck a satellite, which is extremely unlikely (size distribution is going to be a 1/x type of deal). A fleck striking a satellite might kick up ejecta from the hole it leaves, but these secondary flecks will (for the most part) be smaller than the original impacting object. Yes, you'll get more dust, but you won't get many more shuttle-window-puncturing pieces.
Some pathological substances (like paint) may flake off more readily when disturbed, but this is a small fraction of the total mass out there (and paint is vulnerable to abrasion from dust, and so will eventually disintegrate into more dust instead of staying in big flecks).
With many satellites with their own fuel systems, etc, to keep them correctly positioned, you'd better hope that there are fail-safes installed. With space becoming ever-more crowded, we don't need rogue satellites playing astro-pinball.
Space - even the relatively small volume called low earth orbit - is big. Really, *really* big. Even with a few tens of thousands of satellites up there, you'd have to *actively* *try* to hit something to have a reasonable chance of colliding with another satellite any time soon. Debris is a problem because instead of one big chunk of metal flying through space you have a thousand little flecks of paint. *This* does have a chance of striking something (eventually - and that's the key word).
Essentially, Earth would become isolated by an impenetrable barrier of it's own making.
Not a chance. If you're only in low orbit for a short time (like, say, less than a decade), you can go through just about any debris field imaginable without worry. Again, even LEO is *really* *big*, and we haven't really put that much matter up there.
Debris is only a problem if you're planning to stay in the debris zone for years or decades. This makes it a threat to satellites, and to the ISS, and to the shuttle. It's not a threat to space probes, Moon or Mars missions, satellites in higher orbits, or anything else that isn't sticking around in the debris zone. While still significant, and definitely worth doing something about, this hardly qualifies as an "impenetrable barrier".
Not so interesting. (Score:3)
- The decay time of a satellite in a 200 mile orbit is a few months or years. They are pulled into lower orbits by atmospheric drag, and eventually they re-enter. They are not going to stay up long enough to do much of anything.
- If you are proposing that the junk form a ring by loss of energy in collisions, think again. A large amount of the total satellite mass is in polar-orbiting satellites, and some of them are in retrograde orbits. If you equalize their momentum vectors by inelastic collisions, they will lose much of their net velocity and angular momentum. Again, this is a one-way ticket to re-entry.
- The self-gravitation of space junk is minuscule. Even with the addition of the ISS, there are only a few thousand tons of stuff in low earth orbit. This is not enough to accrete by gravitational forces. Tidal forces are much stronger, which would keep any loose aggregation of junk from compacting into a solid body.
The long and short of it is, if we stop launching stuff the problem will solve itself in a few years or tens of years, at least for LEO orbits. Go up a few hundred miles and the situation gets nastier; orbital velocities aren't that much lower, but the influence of air drag is greatly reduced. Space junk can build up there for a time scale of thousands of years. If we keep adding junk to those orbits we will eventually have to go to armored satellites or use something like the "laser broom" to knock stuff into lower orbits which will decay in a reasonable amount of time (hours to years). Another possibility is to get fancy with something to puff up Earth's atmosphere and really increase the drag on the high-level junk, helping to clear out everything that is not able to re-boost itself; something which increases the amount of solar UV or X-rays hitting the upper atmosphere by a large extent is one possibility. Space-junk protection systems are probably going to be an issue for most large space projects in the future.--
Knowledge is power
Power corrupts
Study hard
Very much so! (Score:4)
Then, there's the danger of a chain reaction. One satellite or rocket fragmenting from a collision, generating enough debris that those fragments will, in turn, hit other objects, and so on.
With systems such as Irridium, the probability of a chain reaction became ludicrously high. And, once something like that happens, you don't have anywhere to -put- a "space broom". Essentially, Earth would become isolated by an impenetrable barrier of it's own making.
Then, there is the hazard of the tinier fragments of debris. A fleck of paint can leave a sizable crater in the Space Shuttle's windows. You don't need to be a mathematician to work out the implications of even slightly larger debris striking something like the ISS.
(A ball-bearing could probably punch straight through it, at the speeds we're talking about. And don't believe for a moment that NASA is capable of tracking -every- object that small in orbit.)
With many satellites with their own fuel systems, etc, to keep them correctly positioned, you'd better hope that there are fail-safes installed. With space becoming ever-more crowded, we don't need rogue satellites playing astro-pinball.
Last, but not least, we're in a period of violent solar activity. One -really- good flare could do some really interesting things to the less sturdy sattelites up there.
Not that it really matters, of course. NASA's a lame duck, the ESA has always been into commercial stuff, and nobody else is even remotely close to putting men into space. So the hazards to people are minimal.
The hazards to technology-addicts, though, is extreme. Take out even two GPS satellites, a pager satellite and a TV satellite, and you'd turn most of North America into gibbering idiots.
(The next Ask Slashdot will be debating how you'd tell the difference.)