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JAT Observatory
Space Freak
Reged: 02/20/05
Posts: 5603
Loc: Eastern PA
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the shuttle regularly takes hits from space debris (see image below), and over 80 windows had to be replaced over the years. The ISS occasionally has to take evasive maneuvers to avoid collisions with space junk. And of course, this debris is not just sitting stationary: in orbit, relative velocities can be quite large, ranging in the tens of thousands of kilometers per hour.
Here is a depiction of debris in Leo & Geo orbits.
Another of debris in polar orbit.
The most probable relative velocity between the satellite and a debris object is 52,000 kilometers per hour. If a debris objects hits a satellite, the ISS or the Shuttle, at those speeds it could cause severe damage or catastrophe.
Even after the end of the mission, batteries and pressurised systems as well as fuel tanks explode. This generates debris objects, which contribute to the growing population of materials in orbit, ranging from less than a micrometer to 10 centimeters or more in size.
About 40% of ground-trackable space debris come from explosions, now running at four to five per year. In 1961, the first explosion tripled the amount of trackable space debris. In the past decade, most operators have started employing on-board passive measures to eliminate latent sources of energy related to batteries, fuel tanks, propulsion systems and pyrotechnics. But this alone is insufficient. At present rates, in 20 or 30 years, collisions would exceed explosions as a source of new debris.
Between the launch of Sputnik on 4 October 1957 and 1 January 2008, approximately 4600 launches have placed some 6000 satellites into orbit; about 400 are now travelling beyond Earth on interplanetary trajectories, but of the remaining 5600 only about 800 satellites are operational - roughly 45 percent of these are both in LEO and GEO.
Space debris comprise the ever-increasing amount of inactive space hardware in orbit around the Earth as well as fragments of spacecraft that have broken up, exploded or otherwise become abandoned. About 50 percent of all trackable objects are due to in-orbit explosion events (about 200) or collision events (less than 10).
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-Marcus
The problem with free speech is even the stupid have a voice.
http://jatobservatory.org
12" LX200R on a Paramount ME
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Matthew Ota
super member
Reged: 04/30/05
Posts: 195
Loc: New Hampshire
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From what I have read, there is still no known method to dispose of this space debris. It will be a continuing problem that will only get worse.
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Matthew Ota
10 inch Meade LX250GPS SCT (LX50/LX200GPS clone) f6.3-Orion 80ED, ETX-90 OTA, Coronado Helios 1 H-alpha Solar Telescope
Cassini Huygens Saturn Observation Campaign
New Hampshire Astronomical Society
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Rick Woods
Post Laureate
Reged: 01/27/05
Posts: 4251
Loc: Inner Solar System
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Good grief!
Shields up, Mr. Chekov!
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- Rick
14" LX200GPS
8" Meade 826C
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Treehopper
sage
Reged: 07/29/08
Posts: 215
Loc: Upstate NY
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Eventually, they're going to have to send up a giant vacuum cleaner and suck some of that stuff up. 
Where would you get replacement dust bags for that puppy? 
Maybe we should get that Orrick guy working on this now...
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Tim
Third oak on the right, and straight on 'til morning.
Meade ETX-125PE (NGC7000 Edition)
When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained;
What is man, that thou art mindful of him? and the son of man, that thou visitest him?
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JAT Observatory
Space Freak
Reged: 02/20/05
Posts: 5603
Loc: Eastern PA
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Quote:
From what I have read, there is still no known method to dispose of this space debris. It will be a continuing problem that will only get worse.
But at least NASA and NOAA are writing their specs so the spacecraft manufacturers must have no pressurized vessels remaining after the mission is completed. Explosions from fuel tanks and batteries are the biggest contributor to the growing debris field.
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-Marcus
The problem with free speech is even the stupid have a voice.
http://jatobservatory.org
12" LX200R on a Paramount ME
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Mike K
sage
Reged: 04/01/07
Posts: 460
Loc: Central Texas
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Would it be feasible to deploy a net, possibly something like a thick aerogel sheet with a kevlar backing, to sweep up some of the existing debris, eventually burning it up in the atmosphere?
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Clear skies,
Mike K.
30°31" N 97°44" W, LP: Red
Observe: Once or twice a week back yard, once a month under dark skies
Favorites: Globulars, planets, face-on spirals
Equipment: CPC925/XT10i/TMB-92SS/Lunt LS60THaDS
Eyepieces: Naglers, Ethoi, UO HDs, Hyperion Zoom
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JAT Observatory
Space Freak
Reged: 02/20/05
Posts: 5603
Loc: Eastern PA
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I like the way you think but would have to be a pretty big net. The other issue is some of the items would survive re-entry.
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-Marcus
The problem with free speech is even the stupid have a voice.
http://jatobservatory.org
12" LX200R on a Paramount ME
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Achernar
Post Laureate
Reged: 02/25/06
Posts: 3676
Loc: Alabama, USA
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Many of these rocket stages and satellites were fueled with highly corrosive, explosive, toxic and hypergolic propellants that only have to contact each other to ignite. Over time, these violently reactive fuels can burn through tank walls, valves or fuel lines, then mix and blow apart the satellite or spent rocket stage. Satellites and many upper rocket stages are also pressure fed, meaning only gas pressure forces the fuels into the engine. There are no moving parts except the valves needed to control the flow of propellant to the engine. The pressure to push the fuels to the engines comes from one or more bottles charged with helium or some other gas to pressures of 4,000 psi or higher. That gas is fed from the bottle through pressure regulators into the tanks. Even after the end of the mission, there is still pressurized gas left in these bottles and in the fuel tanks themselves. Rocket stages have blown apart from fuel tank failures and so have satellites, before or after their missions have been completed. That is why rocket stages are commanded to vent all of their excess propellants to space after releasing their payloads.
Taras
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10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
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Mike K
sage
Reged: 04/01/07
Posts: 460
Loc: Central Texas
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Quote:
I like the way you think but would have to be a pretty big net. The other issue is some of the items would survive re-entry.
I can color an entire sheet of paper with the tiny point of a pen... the net need not be so huge, it just needs to trace out a path covering a large area. Of course, you would have to avoid satellites and things that you want to leave in orbit.
As for surviving reentry, would it be better to bring them down even if they survive reentry, or to leave them up there as threats?
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Clear skies,
Mike K.
30°31" N 97°44" W, LP: Red
Observe: Once or twice a week back yard, once a month under dark skies
Favorites: Globulars, planets, face-on spirals
Equipment: CPC925/XT10i/TMB-92SS/Lunt LS60THaDS
Eyepieces: Naglers, Ethoi, UO HDs, Hyperion Zoom
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JAT Observatory
Space Freak
Reged: 02/20/05
Posts: 5603
Loc: Eastern PA
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Quote:
I can color an entire sheet of paper with the tiny point of a pen... the net need not be so huge, it just needs to trace out a path covering a large area. Of course, you would have to avoid satellites and things that you want to leave in orbit.
I hope you have a lot of ink cause there is a lot of space.
Never mind avoiding things you want to keep, what about matching your velocity and direction to the stuff you want to catch? Its not all moving at the same speed and direction.
You also have to remember some of the stuff has a lot of mass. Assuming you don't become another piece of debris in process it takes energy (which = fuel which = money) to change direction while towing a large mass. The more fuel you need the higher your launch cost.
Quote:
As for surviving reentry, would it be better to bring them down even if they survive reentry, or to leave them up there as threats?
Depends how do you plan on controlling the reentry of this mass of junk. There would have to be a lot of it in order to make the process cost effective. So you will need to control where it comes down. Unless we just left it up there like a giant space hairball. Eventually there might be enough of them and they would coaless and create a new moon.
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-Marcus
The problem with free speech is even the stupid have a voice.
http://jatobservatory.org
12" LX200R on a Paramount ME
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Mike K
sage
Reged: 04/01/07
Posts: 460
Loc: Central Texas
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Excellent points.
My thinking was geared mostly towards the small debris, I think you mentioned a lot of it was between a micron and 10cm in size. Seems like you should be able to calculate an orbit that would sweep across a reasonably large area over say 10 - 15 years, even if the physical size of your net is modest. You would need enough fuel to maintain a proper orientation relative to your direction of travel. The orbit could be designed to eventually decay and burn up in the atmosphere, along with any debris you have "swept up".
Larger objects present a somewhat more difficult problem, but I would assume that they make up a smaller percentage of the overall debris population.
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Clear skies,
Mike K.
30°31" N 97°44" W, LP: Red
Observe: Once or twice a week back yard, once a month under dark skies
Favorites: Globulars, planets, face-on spirals
Equipment: CPC925/XT10i/TMB-92SS/Lunt LS60THaDS
Eyepieces: Naglers, Ethoi, UO HDs, Hyperion Zoom
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Matthew Ota
super member
Reged: 04/30/05
Posts: 195
Loc: New Hampshire
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Besides, how could you get a vacuum cleaner to work in a vacuum?
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Matthew Ota
10 inch Meade LX250GPS SCT (LX50/LX200GPS clone) f6.3-Orion 80ED, ETX-90 OTA, Coronado Helios 1 H-alpha Solar Telescope
Cassini Huygens Saturn Observation Campaign
New Hampshire Astronomical Society
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molniyabeer
Carpal Tunnel
Reged: 01/08/05
Posts: 2029
Loc: Central Coast, California
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One of the nice things is that low earth orbit, at least, is somewhat self-cleansing due to atmospheric drag. As we move into solar maximum in a few years, the extra solar activity will heat up the atmosphere and puff it out a bit. The extra drag quickly adds up on satellites in LEO, their orbits decay, and they burn in.
Now, if you could figure out a way to go retrieve all that junk up at the geosynchronous belt, I suspect there are some satellite operators who would love to get their slots cleaned up...
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Steve
16" Meade LightBridge (Beowulf)
10" Hardin DSH, StarMax 127mm Mak, PST H-a
Oberwerk 11 x 70 binocs, Tasco 10 x 50 binocs
Santa Maria Clear Sky Clock
Figueroa Mt Clear Sky Clock
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