The Space Garbage Scow, ala Cringely 221
An anonymous reader writes "Robert X. Cringely once again educates and amuses with his take on how we could clean up the garbage that's in orbit around Earth. I cannot vouch for his math, but it makes sense to me. Quoting: 'We’d start in a high orbit, above the space junk, because we could trade that altitude for speed as needed, simply by flying lower, trading potential energy for kinetic. Dragging the net behind a little unmanned spacecraft, my idea would be to go past each piece of junk in such a way that it not only lodges permanently in the net, but that doing so adds kinetic energy (hitting at shallow angles to essentially tack like a sailboat off the debris). But wait, there’s more! You not only have to try to get energy from each encounter, it helps if — like in a game of billiards or pool — each encounter results in an effective ricochet sending the net in the proper trajectory for its next encounter. Rinse and repeat 18,000 times.'"
Re:Cringely is an idiot. (Score:5, Informative)
You could try reading the summary next time. His proposal was for one flight, not 18000. I imagine his plan is still impractical for lots of reasons (you probably can't get enough impulse from each piece to approach the next one at a low enough speed, etc.), but it's still not as bad as your suggestion of 18000 manned space flights.
Re:Wouldn't that be bad when it re-enters? (Score:4, Informative)
The problem with space junk is that there's thousands of piece of it flying around that can damage spacecraft, re-entry isn't really the problem. That's actually preferable to losing a few of your spacecraft to loose pieces of material in orbit.
Re:Make sure. (Score:3, Informative)
I suppose you're catching stuff in a net travelling in the same direction as the junk so it'll be a gentle catch rather than a hard collision. That shouldn't create any more micro bits of shrapnel.
Re:Conservation of energy/momentum (Score:4, Informative)
Something like this will be needed after.... (Score:1, Informative)
The Chinese pre-emptively launch a billion piezo electric pebbles into all the military sattelite paths just before they invade Taiwan and the petroleum rich areas of the Philippines, thus sweeping all comm links and observation platforms from the sky in a matter of an hour. As well as every other satellite. to re-build the world after the[a href="http://www.missilethreat.com/missiledefensesystems/id.13/system_detail.asp">Brilliant pebbles attack, we'll need a scow.
So it won't really matter if a few things break up. Space won't be habitable at all till some clean up is done.
Re:Wouldn't that be bad when it re-enters? (Score:3, Informative)
Re:"net"? (Score:4, Informative)
Radius of the earth:
Re = 6,378 km
Low earth orbit starts at ~200km:
Rleo1 = Re + 200km = 6,578km
Low earth orbit extends up to about 2000km ( it's debated. Using nice round numbers )
Rleo2 = Re + 2000km = 8,378km
4/3* PI * ( Rleo2^3 - Rleo1^3 ) = 1.271E12km^3
1.3 trillion cubic kilometers of space to sweep.
Assume a block of aerogel 10 meters on a side - so a frontal area of 100 m^2. That's pretty big, and it won't get any bigger unless we figure out how to manufacture the gel in space:
Agel = 100m^2
= 0.0001km^2
Velocity in leo is around 7.5km/second, relative to the ground.
Vgel = 7.5km/s
Let's assume that we are just trying to sweep the entire volume of space once, ignoring that things are moving etc. Even one sweep of the volume would certainly clean up a lot, if the orbit of the gel is tangent to the orbit of most of the junk. So we just pretend that the block of gel is flying down a tunnel, basically - frontal area times velocity * time equals volume cleaned:
Vclean = Agel * Vgel
1.27E12km^3 =
t = 1.695E15 seconds
= 5.37018E7 years
= 53 million years.
Re:Cringely is an idiot. (Score:1, Informative)
correction: the proper link would be this one [nasa.gov].
Re:Wouldn't that be bad when it re-enters? (Score:5, Informative)
Just wanted to point out that for the first time in the history of slashdot, you correctly spelled "losing" and "loose" in the same sentence. The content of your point is good too!
Re:Wouldn't that be bad when it re-enters? (Score:3, Informative)
Good point. Probably should be km/h?
Re:Wouldn't that be bad when it re-enters? (Score:2, Informative)
At speeds above Mach 8.0, you can drive a pencil through a 100mm armor steel plate - even the pencil tip stays intact and sharp.
Speed is relative. If the net is moving in the same direction in the same orbit at a lower speed, impact speed is far less than travel speed and force can be distributed over time.