[tw04]

I would imagine he means trying to navigate the debris when sending other stuff into orbit, or bringing spacecraft home. I've often wondered this myself... at some point do we have so much stuff up there it's near-impossible to get spacecraft out without serious danger to their crews? And what about when it's time to retire them?

Legitimate question.

[eckzow]

You may find this Wikipedia page enlightening: http://en.wikipedia.org/wiki/Kessler_syndrome

[pietro42]

If my napkin-calculations are correct, 4025 stats @ 1100 km LEO orbit would occupy 0.0000000573% of the sky - so not a real problem, I believe ;) (if they are in the same plane, that is and each have 10mx10mx10m bounding area...)

  ((10/1000)**2*4025)/(4*pi*(6371+1100)**2)*100 %