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mopc
2004-Jul-03, 04:54 PM
They say space littering has already become a major risk for space travel. But given that any object in an orbit is travelling at the same speed than the others (Gallileo!), space debris would only be an issue if it were traveling in the opposite direction, right?

Even then, how likely do they estimate today that a spacecraft is hit by debris???

Glom
2004-Jul-03, 07:08 PM
In a given orbit things are simple. For example, in geostationary orbit, there are hundreds of satellites but because they are all moving in the same way, it's not a problem.

However, what about shapes of orbit? Orbits of different eccentricity etc? Different shapes of orbit will cross each other and because they may have different periods, their movement will not be in synch. Things can get a bit randomised after a while.

The major problem are flecks of paint and spent boosters and coverings that may be on a variety of orbits such as elliptical transfer orbits used to get satellites up to a certain altitude.

Arf
2004-Jul-03, 07:19 PM
This is my first post here (though I've lurked for quite a while), so I hope I don't get anything drastically wrong...

Anyway, though it is correct that objects with orbits of equal radii will have the same speeds (assuming circular orbits), their directions can easily be completely different. I'm sure I've seen a diagram somewhere showing the positions of the largest chunks of known space "litter", and they're pretty much spaced out across every possible orbit around the earth. Even if they're not travelling in exactly opposite directions a collision could still be very dangerous, given a large enough chunk of debris.

I don't know current estimates, but I think there has only been one notable incident involving space debris, where something struck the space shuttle (though no serious damage was inflicted), but I'm not completely sure of that. Obviously the general view is that the likelyhood of a dangerous collision isn't sufficient to prevent travel in space.