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Author Topic: Why is small space debris not a bigger problem?  (Read 3263 times)

Herman Melville

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Why is small space debris not a bigger problem?
« on: 02/07/2009 11:28:09 »
There are supposedly more than 600,000 objects larger than 1cm orbiting the Earth. Most of these are inactive satellites, bits of broken spacecraft or lost equipment (spanners, etc).





A few questions:
1. Why aren't these items causing more problems for rockets/satellites/the Space Shuttle etc? They must be moving at quite a speed and impact with a moving craft would be huge.

2. Can anything be done to 'clean up' the space junkyard?

3. Can all the debris be mapped/charted?

4. Will there eventually be no safe orbit routes due to the amount of debris?

5. Is there a danger of this stuff raining down on us at a future date?




 

lyner

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Why is small space debris not a bigger problem?
« Reply #1 on: 02/07/2009 11:52:17 »
I believe that there have been collisions.
The OLYMPUS satellite, which was a relatively early vehicle for Direct Broadcasting by Satellite was though to have been hit on one of its photocell panels and was sent spinning. It took some time to get it under control again. I happen to know about that one because I was involved in early DBS of HDMac HDTV signals. A collision would only be newsworthy if the collision involved a human.

Despite the huge number of bits of junk, there is an awful lot of space in between them. On similar lines, early Sci Fi books used to suggest that "flying through the Asteroid Belt" would be hazardous. In fact, I believe that you'd be hard pressed to spot one, let alone collide with one on the way through.
 

Offline LeeE

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Why is small space debris not a bigger problem?
« Reply #2 on: 02/07/2009 15:42:56 »
Yes, I'm sure I've heard of a few collisions too.

It's difficult to clean them up because you'd have to match orbits with each individual item, with the item playing a purely passive role, and relying solely upon the retrieving craft's sensors to make a safe rendezvous - tricky for something as small as a single threaded nut, for example.

Most of the items have been mapped.

Congestion is already a problem for some locations/orbits.

There's no danger from any of this stuff raining down on us because it's all mostly small bits and pieces that will burn up on re-entry.
 

lyner

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Why is small space debris not a bigger problem?
« Reply #3 on: 04/07/2009 01:55:38 »
The only viable solution may be to zap them with a high power laser, rendering them into harmless dust, most of which will either be pushed into re entry or kicked out into deep space at more than escape velocity.
 

Offline Ophiolite

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Why is small space debris not a bigger problem?
« Reply #4 on: 04/07/2009 02:15:32 »
While the speed of the items is high relative to the Earth, the speed of most objects relative to each other is quite low.
 

lyner

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Why is small space debris not a bigger problem?
« Reply #5 on: 04/07/2009 09:08:05 »
Is that true for objects in polar orbits when they meet objects in equatorial orbit?
 

Offline Ophiolite

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Why is small space debris not a bigger problem?
« Reply #6 on: 04/07/2009 10:51:33 »
Is that true for objects in polar orbits when they meet objects in equatorial orbit?
Clearly not. That is why I used the qualifier 'most'.
 

lyner

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Why is small space debris not a bigger problem?
« Reply #7 on: 04/07/2009 13:13:50 »
OK.
My logic is not at its best that early in the morning.
I wonder how the probability of 'crossing orbit' collision compares with the probability of  'shared orbit' collision.
« Last Edit: 04/07/2009 13:16:53 by sophiecentaur »
 

Offline Ophiolite

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Why is small space debris not a bigger problem?
« Reply #8 on: 04/07/2009 22:08:04 »
Overall there clearly is a significant risk. As long ago as 1990 the Office of Technology Assessment of the US Congress observed " Unless nations reduce the amount of orbital debris they produce each year, future space activities could suffer loss of capability, loss of income, and even loss of life as a result of collisions between spacecraft and debris."

This was borne out by the collision in February this year between Kosmos-2251 and an operational Iridium 33 over northern Siberia with an impact speed of approxiamtely 11.7 kilometres per second. In this instance the Kosmos was on an approximately equatorial orbit, while the Iridium was on a polar orbit, the very situation you are interested in.

Numerous models have been developed to assess collision risk and while these give order-of-magnitude comparable results, they clearly require further development.

The main collision risks, quite logically, exist for objects in low Earth orbit (LEO) rather than MEO or GEO. There are more of them and there is a smaller volume into twhich they are packed. (Space (incidental pun) is at a premium in geosynchronous orbit, but these orbits are carefully monitored and controlled. Also deactivated satellites are moved into other positions away from collision risk.)

So far I haven't found any specific risk figures for polar, versus equatorial collisions. I'll keep looking.
 

Offline Bored chemist

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Why is small space debris not a bigger problem?
« Reply #9 on: 05/07/2009 14:01:07 »
In order to colide the two objects must be at the same altitude. For circular orbits if they are at the same altitude they have the same orbital period. If they didn't hit each other on their first trip round the earth they won't hit eachother now. Collisions should be rare except where the orbits are far from circular for some reason.
 

lyner

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Why is small space debris not a bigger problem?
« Reply #10 on: 05/07/2009 16:36:27 »
The point is that the orbits may have started off circular but they are in an unstable situation because of the Moon, Sun and other stuff. They will end up in elliptical orbits. Not highly so but significant. If one on it's perigee meets one ok it's apogee, the speeds can be different.

There is always the possibility of small stuff being pulled onto a wildly eccentric orbit as the result of a near collision with a big object and a slingshot effect. These maverics could cause serious incidents - rare tho'.
 

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Why is small space debris not a bigger problem?
« Reply #10 on: 05/07/2009 16:36:27 »

 

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