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ToSeek
2006-Jul-31, 03:30 PM
Orbital Debris a Growing Problem with No End in Sight (http://www.space.com/spacenews/060731_businessmonday.html)


The proliferation of garbage in low Earth orbit has reached a point where it will increase in the coming decades even if all rocket launches were canceled starting now, according to research by NASA’s Johnson Space Center.

The satellites and rocket stages designed and launched before the seriousness of the problem was recognized are like time bombs, waiting to break apart in the coming years on combustion of their remaining fuel thereby multiplying the pieces of space garbage.

At some point, the growing population of orbiting debris increases the likelihood that pieces will collide into each other, spawning still more space junk.

The problem is especially acute at altitudes of between 900 and 1,000 kilometers.

NEOWatcher
2006-Jul-31, 04:20 PM
Orbital Debris a Growing Problem with No End in Sight (http://www.space.com/spacenews/060731_businessmonday.html)

I guess, in short, that the rate of break-ups have just now met or exceeded the rate of re-entries.

Now realistic solutions (http://www.bautforum.com/showthread.php?t=44512)?

loglo
2006-Jul-31, 05:17 PM
I made a fairly flippant post a while back (shortly after the Stardust mission returned) about using panels of aerogel to capture the smaller particles of junk in orbit. I've been thinking about it on and off expecting to be able to shoot the idea down fairly easily but haven't been able to do so yet.

So what is to stop us sending a few dozen panels of aerogel up into low orbit. You attach them to electromagnetic tethers which can re-boost them periodically and de-boost them when they have collected enough junk. Sure they aren't going to stop the big bits but those can be tracked and compensated for. Its the increasing amounts of smaller, non-trackable particles, especially from a cascading break up event, that could cause the biggest problems over time.

It seems too simple to work, so probably won't. But why?

gwiz
2006-Jul-31, 05:27 PM
Are the particles that are small enough to be caught in aerogel big enough to worry about?

NEOWatcher
2006-Jul-31, 05:40 PM
Let's say we can make an Aerogel 10mx10m
At 900-1000 km alt. we have a volume of around 30bil km2
That orbit is about 7km/sec or around 220bil m/year
So the array sweeps a volume of around 22,000 bil m/yr or about 22 Mkm2 per year.
Or about 1400 years to sweep a volume equal to the size of the area.
And this doesn't consider fuel, longevity, orbit changes due to the collisions, items that can be captured, risk of the collector contributing to the problem, and I'm sure there's much more.

loglo
2006-Jul-31, 05:52 PM
Are the particles that are small enough to be caught in aerogel big enough to worry about?


They will be if they become numerous. They may not take out a satellite but they could make spacewalking dangerous. The stuff I'm talking about is still a few mm across but is still capable of packing a punch when travelling at orbital speed. I took this from a BBC article at http://www.bbc.co.uk/science/space/solarsystem/earth/spacejunk.shtml:-
"What are the dangers from debris?

Although most of the debris in space is small, it's travelling extremely fast. Below altitudes of 2,000 km, the average relative impact speed is 36,000kmph (or 21,600 mph). At this speed, collision can be dramatic:
* A 1mm metal chip could do as much damage as a .22-caliber long rifle bullet
Bits this size don't generally pose a large threat to spacecraft, but can erode more sensitive surfaces and disrupt missions.

* A pea-sized ball moving this fast is as dangerous as a 400-lb safe travelling at 60 mph
Debris this large may penetrate a spacecraft. If this happens through a critical component, such as the flight computer or propellant tank, this could be fatal.

* A metal sphere the size of a tennis ball is as lethal as 25 sticks of dynamite
This debris will penetrate and seriously damage a spacecraft. "

It also says that "NASA frequently replace windows on the space shuttle that have been damaged by objects as small as a flake of paint."

The problem is definitely real, there are estimated to be a million pieces smaller than a tennis ball. If a runaway cascade occurs, where particles from an impact creates more impacts and more particles, then LEO could become unusable.

Doodler
2006-Jul-31, 06:03 PM
The problem is definitely real, there are estimated to be a million pieces smaller than a tennis ball. If a runaway cascade occurs, where particles from an impact creates more impacts and more particles, then LEO could become unusable.

From the tone of the article, it sounds like we're to the point where junk is creating more and more smaller junk of its own accord, without needing new launches to replenish the debris field.


I am curious. The volume of junk to the volume of space in LEO is still pretty tilted in favor of empty space. Add to that launches which tend to follow a set series of orbital inclinations. Is the debris field a full volume problem, or is it certain orbital tracks which are becoming a problem? And if it is just a string of particular tracks, is it possible, as we start getting a clue and adjusting our hardware to become less a problem with this, that we could adjust our launch tracks into orbital planes where the difference between the littered tracks and the new tracks is such that collision threats are lowered? It'll be inconvenient, sure, but is that a reality, or is the problem more evenly distributed that such precautions are pointless?

jseefcoot
2006-Jul-31, 08:54 PM
The problem, I think, is less the amount of debris than the particular danger it poses: any debris up there can be deadly. A Low Earth Orbit makes it that much more hazardous because then things are 'raining down' on you.

Our launch paths are somewhat limited by the weather, the Earth's rotation, the location of the launch platform, and the expense of launching, making it difficult to avoid areas where debris can be found. Some trajectories cost more than others if they require longer burn times to reach escape velocity. Our biggest obstacle to solving/avoiding this problem is cost.

There was another post on this forum, just a week or two ago, discussing this very topic. Many people discussed ideas regarding capturing this stuff, usually with the intent of recycling it, sometimes to cart it off somewhere to eject it into deep space or whatever. I maintain (then and now) that the easiest and cheapest way to rid ourselves of this stuff is to somehow cause it to burn up sooner, maybe by using a sturdily built, fuel-laden and fuel-efficient craft to 'bump' things into orbital decay sooner than they would have done on their own. There is no way that recycling this stuff would be worthwhile -- our launch technology would have to improve dramatically to make that many trips back and forth (or to build and maintain some kind of permanent orbital recycling station -- or for that matter to build a maneuverable, sturdy and fuel efficient orbital craft to push this junk around). There's not much up there that can physically damage the Earth in the event of a collision; I doubt that most things up there will even make it to the surface anyway.

Humankind now has more of a presence in space than ever before. It's an important issue that really should be addressed now, but I fear that it too will fall by the politically budgeted wayside.

gwiz
2006-Aug-01, 10:50 AM
It's not just a matter of a certain track being contaminated by debris from a satellite break-up, the stuff spreads. In the first place, some of the debris is travelling faster than other bits, so the debris spreads out along the orbit, each piece in a slightly different trajectory, changing from a spherical cloud to a torus. Secondly, the rate at which the plane of the orbit precesses depends on the orbit, so different debris bits precess at different rates. The torus thus grows in the east-west direction until it becomes a shell right around the earth. At this stage, even a satellite in a similar orbit to the original break-up can meet a piece of debris that is in a widely different orbital plane, with a relative velocity of several km/s.

loglo
2006-Aug-01, 12:57 PM
Let's say we can make an Aerogel 10mx10m
At 900-1000 km alt. we have a volume of around 30bil km2
That orbit is about 7km/sec or around 220bil m/year
So the array sweeps a volume of around 22,000 bil m/yr or about 22 Mkm2 per year.
Or about 1400 years to sweep a volume equal to the size of the area.
And this doesn't consider fuel, longevity, orbit changes due to the collisions, items that can be captured, risk of the collector contributing to the problem, and I'm sure there's much more.


Cheers NEOwatcher, came to pretty much the same conclusion myself. I think if we narrow down the volume to the most common orbital planes and stick more than one up there at a time then this becomes a more reasonable prospect.

If you could use an electro-magnetic tether, especially in LEO, this would mitigate the cost and increase the lifetime. I don't see any showstoppers here except for the risk of contributing to the problem itself by disintegrating on impact with something large.

NEOWatcher
2006-Aug-01, 03:02 PM
Cheers NEOwatcher, came to pretty much the same conclusion myself. I think if we narrow down the volume to the most common orbital planes and stick more than one up there at a time then this becomes a more reasonable prospect.
Still a major undertaking, and more collectors mean more risk.

If you could use an electro-magnetic tether...
Are you proposing the EM to be the collection mechanism? If so, that doesn't work to well on aluminum.

...especially in LEO, this would mitigate the cost and increase the lifetime.
Unfortunately, LEO is not the problem.

In the end though, I do think the issue needs to be resolved.

loglo
2006-Aug-01, 07:36 PM
Are you proposing the EM to be the collection mechanism? If so, that doesn't work to well on aluminum.

No, just for orbital maneouvering including reboosting and deorbiting.
See here (http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=252) for an example.



Unfortunately, LEO is not the problem.

Quoting from the Wolfram site
"However, if serious attempts to clean up low-orbit space are not made sometime soon, an artificial asteroid ring could form around earth that would endanger any object having to pass through it."

From Wikipedia:-
"Space debris is most concentrated in low Earth orbit, though some extends out past geosynchronous orbit."

Low orbit is definitely a problem. GEO may be where most of the hardware is, but you have to go through LEO to get there. And LEO is where the most expensive single piece of hardware is, the ISS.

NEOWatcher
2006-Aug-01, 07:59 PM
Low orbit is definitely a problem. GEO may be where most of the hardware is, but you have to go through LEO to get there. And LEO is where the most expensive single piece of hardware is, the ISS.
Although the artical does say that the upper portion of LEO is the biggest problem (only because I'm splitting hairs). :think:
I was trying to look for it, but couldn't find it...but... it was a chart that showed orbital decay rates for various altitudes. It made me think that the lower LEO is not an issue because the decay rate is in the low decades, and its the somewhat higher orbits that take a long time to decay that is the problem. But without the chart, I can't remember where those points were.
And where the ISS is, it seems almost self cleaning (although still a problem). I believe that's one of the reasons it is where it is, and I infer that from this chart. (http://www.heavens-above.com/issheight.asp)

Doodler
2006-Aug-01, 08:03 PM
The bulk of the problem looks to be above the LEO realm of the ISS and Space shuttle. Not that this won't become a problem as their orbits decay...

Ronald Brak
2006-Aug-02, 04:47 AM
Here's a silly question. How much insolation is this space junk likely to be blocking? My rough estimate is about 0.000 000 000 1%.

BigDon
2006-Aug-02, 05:08 AM
I just had a thought.

Would any of you guys be mad at me if I went to one of the conspiracy web sites and tried to start a rumor that all the orbital debris is really a "secret goverment defense shield" to protect us all from alien abduction and such, or would that be counter to the spirit of this forum? At least then we would have the advantage of knowing where it came from. We could then time it to see how long it took to get back to us. Aww, I guess I won't. No sense making Mr. Plait's job any harder than it is already.

:)
BD

ToSeek
2006-Aug-03, 06:20 PM
One of our residents makes a hobby of doing that, but, yes, the BA tends to frown on it. There's enough misinformation out there already without adding to it.

loglo
2006-Aug-04, 01:03 AM
The bulk of the problem looks to be above the LEO realm of the ISS and Space shuttle. Not that this won't become a problem as their orbits decay...

And if it is being generated continuously this amounts to a steady rain of junk through LEO. I just like the idea of a big blob of jelly floating around sucking up junk. You could make them in shapes of your choice, imagine a big Spongebob floating past the ISS. Gotta be worth it for the comic relief alone! :dance:

jt-3d
2006-Aug-04, 03:20 AM
I saw some debris sail over last night. While looking for that comet with binoculars, I saw what I guess was Cosmos 1603 Rocket4 sail over, so sometimes trash is cool. Never saw the comet though.

NEOWatcher
2006-Aug-04, 04:05 PM
... I just like the idea of a big blob of jelly floating around sucking up junk...
NO, no, no. No more remakes of the blob. :hand:

Ronald Brak
2006-Aug-05, 11:25 AM
There are people who want to mine asteroids. I say why go so far? It will be a while however before we have the technology to make capturing and using space junk cheaper than just shooting more stuff into space from earth. But anyone who thinks mining asteroids is economical and salvaging space junk isn't needs to sit down with a pencil and paper for a while.

Wolf-S
2006-Aug-05, 11:46 AM
And if it is being generated continuously this amounts to a steady rain of junk through LEO. I just like the idea of a big blob of jelly floating around sucking up junk. You could make them in shapes of your choice, imagine a big Spongebob floating past the ISS. Gotta be worth it for the comic relief alone! :dance:And then there would be some kind of SpaceTrash@Home. "Find 40 rocket stages in the blob" ;)

Dave J
2006-Aug-05, 02:55 PM
When I took my space systems engineering course, we designed a satellite system. Now, we were told that modern satellites are designed with the space debris problem in mind, and that at the end of the useful life, they are boosted to a orbit of less conflict, or deorbited. Is this really the case?
Also, if you think about the 21600mph average relative impact speed, this would assume that the objects are orbiting opposite each other to some significant degree, as orbital velocity is only around 17000mph. Is there that much retrograde orbit stuff out there?

publiusr
2006-Aug-17, 09:18 PM
I think we need smaller numbers of larger, shielded craft:
http://www.astronautix.com/craft/globis.htm

http://www.astronautix.com/craft/intaltug.htm

"...the interorbital tug Gerkules with 550 kWt maximum output and continuous operation in the 50-150 kWt range for 3 to 5 years. In 1986 a civilian interorbital tug was studied to solve the specific application of transporting heavy satellites of 100 tonnes to geostationary orbit, launched by Energia. All of these designs seem to have been essentailly similar; the figures given here are for the last study. The tug would have a propellant supply adequate for 16,000 hours of operation and three years of reactor life. "


http://www.astronautix.com/stages/erta.htm

http://www.astronautix.com/engines/11b97.htm

Launched by this of course:
http://www.nasa.gov/pdf/151420main_aresV_factsheet.pdf
http://www.astronautix.com/lvs/magnum.htm

Captain Kidd
2006-Aug-17, 09:50 PM
There's even an anime out about this called Planetes (Anime News Network (www.animenewsnetwork.com/encyclopedia/anime.php?id=2654) | Wikipedia (http://en.wikipedia.org/wiki/Planetes)). The DVDs contain interviews with NASA's Orbital Debris Section Scientists about... well, orbital debris.