Space Junk: Aging & Decomposition Rates

[bobbobwhite]

Has there been any real scientific testing to determine the ratio of aging or decomposition of space junk above our atmosphere compared to atmospheric aging? I ask this because if space junk is going to be "out there" for millions of years as is, why would we even consider adding more in the form of space stations, commercial satelites, etc. if it will be there forever and be an eternal and ever increasing obstacle to future space travel or research vehicles?

Thanks for any informed answers, and if this is not the correct forum for this question please direct me to the correct one.

 

[mgb_phys]

It's very dependent on altitude.
Low Earth Orbit (say 300-500km) where the shuttle, ISS, GPS, Earth observation satelites live is reasonablty crowded and so the chance of a colission is real (as happened recently)
But atmospheric drag is a large effect, objects that aren't periodically boosted will be slowed by the atmopshere and re-enter, the positive side of this is that space junk is removed fairly quickly. The amount of atmospheric drag is very difficult to calculate since it depends on the interaction of the sun and the outer atmosphere - this has been a very low activity sun cycle and so the atmosphere has been very low for along time.

At higher (eg geostationary) orbits) there is a lot more space (!), satelites aren't moving relative to each other and so collisions are very unlikely. However if there was a collision or a satellite exploded (accidentally or deliberately) the junk would stay there pretty much for ever.

 

[bobbobwhite]

The closer to Earth's atmosphere the space junk is, the faster the decomposition, or removal by re-entry. That seems obvious. What I want to know: would there be no effective contact friction, solar weathering, or material fatigue in outer space that would eventually decompose the materials comprising the junk in, e.g., millions of years? I would think that, of these three factors, at least solar and fatigue would still play a function in eventual decomp, even in space.

Why and how we would test millions of years of solar weathering, materials friction and fatigue in space in our limited human years is probably unanswerable, as surely at the top of the list of reasons is that so far there is no money to be made by it. The next would be, other than bobbobwhite, who cares? All I can say is that the question intrigues me as we continue to "trash up" outer space as we have our earth.

 

[mgb_phys]

In space you will have a lot of UV photons from the sun that will break down most plastics. Micrometeorites and dust will eventually wear down and break up any other structures but that will take a while

 

[bobbobwhite]

Thanks for your conversation. The whole space junk issue surely doesn't mean anything anyway, as humans will not be around long enough to be affected by increasing space junk in any future space travel attempts. We will be long gone before any potential of that will be a factor. I can only hope and wish for whatever our legacy may be that human-caused space junk will not be the last unfortunate signs of our short existence on the cosmic calendar to any other possible life "out there".