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Giant Balloons Could Solve Space Junk Problem
An anonymous reader writes "More than 100,000 objects bigger than a centimeter wide hover around our planet, accounting for 4 million pounds of junk that befouls our atmosphere and threatens the expensive satellites we actually want in orbit. Dr. Kristen Gates, of Global Aerospace Corporation, proposes that we can clear the skies by attaching a football field-sized balloon to dead satellites, which would increase the orbital drag, eventually bringing a satellite down into the atmosphere where it would burn up. The GOLD — or Gossamer Orbit Lowering Device — unit is easily inflated in space, and best of all, if the deployed GOLD balloon collides with space junk, it won't deflate or break the junk into smaller, less manageable bits."
Ok, you've grappled the object. Where do you want to send it?
Sending it down requires a drag chute of some kind. Or it requires just enough delta-v to drop its perigee just a little lower into the atmosphere.
Suppose we had the mother of all factories sitting in equatorial orbit. Suppose your space junk is in a 35 degree orbit. Both objects are traveling at around 27Kkm/h if they're in a relatively low orbit. However, one object is moving 27Kkm/h due east, and one is moving 27Kkm/h 35 degrees north of east. Relative to each other they are moving at thousands of kilometers per hour when they pass each other. To collect the object you need to apply that much of a velocity change to it, which is a huge amount of energy (not quite what it took to launch, but we're getting into that kind of magnitude).
Think of it this way - you're on a racetrack going 200mph. Another car is going 200mph the other way. You want to collect it. How do you do this without massively changing its velocity?
One of the first rules of orbital mechanics is that plane changes are expensive. That's why the shuttle can't visit the ISS and the hubble on the same mission. They're both in similar altitude orbits, but in different planes. The shuttle doesn't have enough fuel to change planes (at least, not that far - and without looking up the numbers that is probably only 10 degrees or so).