Assuming you manage to grab a hold of debris without ripping off even tiny parts, how would you dispose of it? You'd need to deorbit it and you need a working engine for that. So a reusable collector doesn't seem like a plausible concept to me.
meet up with the debris, reorient yourself and the debris such that the debris is closer to the earth (reaction wheels, magnetic torquer bar and patience is all that's required), and then just mechanically kick it down (store up energy from the sun and then trigger a solenoid). the debris itself becomes your propulsion. you get a tiny boost up, perhaps towards your next target, and it gets a (admittedly!) tiny boost down.
obviously it doesn't instantly dispose of everything, but progressively pushing material further down the gravity well is the next best thing.
not claiming this would be cost effective.
This doesn't actually work. If you push something down in orbit, you just make its orbit elliptical. After half an orbit it will be at the same altitude as you again, and after a full orbit it will hit you from the top. If you want to lower its orbit, you need to push it back.
Orbital mechanics is weird.
Came here to say this as well! The only caveat to that I can think of is if you're already low enough in orbit, the push making the satellite's orbit elliptical could put it in a drag zone, and then air would do the slowing down for you.
Also, thank you Neal Stephenson for introducing me to the wonderful would of orbital mechanics via Seveneves!
The Kerbal never got back to his ship before running out of propellant.
if you want to lower its orbit, you probably need to take a lot of complicated stuff in to account which doesn't fit into a comment. i won't charge the orbital dynamacists implementing my idea more if they replace "down" with "the optimal direction for this target, at the optimal moment".
mass of the target, cross sectional area of the target, any out gassing it might be doing, where we're trying to maneuver to next, etc, etc.
if the optimal direction ends up being exactly "down" or "back", i'll buy you a beer.
You may be to do this with atospheric drag if you add enough ellipticity but they would only be lowering the orbit indirectly.
you know, in the wildly hypothetical world where this was implemented, i don't think the folks cutting the check would mind if you deorbited things directly, or indirectly.
There are some ideas that could be repurposed from asteroid mining concepts. Many asteroids are more like pile of gravel loosely bound by gravity than solid rocks, and either way, trying to extract anything risk launching lots of tiny pebbles in a random directions. One idea I saw floating around NASA website was to wrap such an asteroid in a net or sheet of material, to keep it from shaking itself apart. I could imagine similar lightweight net being used to wrap a satellite.
Once wrapped, you can do two things with it. You can try to deorbit captured trash - for instance, with a light net and a solar sail attached (which would be used to increase atmospheric drag). Such trash would not only deorbit faster, but a sail would make it easier to track. Nets and sails would have to be light and disposable, they could be shipped to orbit in bulk, or (later) manufactured in space.
Alternatively, you can try to recycle the trash. If you have in-orbit refueling using propellant sourced from space, you probably already have - or are about to have - some facility in orbit that could reprocess parts of dead satellites. So you can move the trash to some designated recycling orbit.
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Now that I think of it, you could probably make a recycling collector work without all the infrastructure in space. In orbit, you have time, you can take things slow. I can imagine a collector chasing light trash using ion thrusters, or whatever is most promising in high-Isp department these days (how small can a VASIMR get anyway?), grabbing it and parking at the recycling orbit. Might take weeks per piece of trash, but if you launch a bunch of such collectors and feed them trajectories from the ground, they'll eventually clean the orbit out of light trash. It might require some actual developments in the beamed power department, and perhaps launching a power satellite to microwave some electricity to the collectors, but think it would work in (sufficiently modded) KSP :). Anyway, the biggest problem isn't mission design, but figuring out who will actually pay for this.
Not sure what to do about the most dangerous space trash - the tiny bits that can't be reliably tracked. Track them better and vaporize with lasers?
Another very 'interesting' idea is deploying a large amount of fine dust on an appropriate polar orbit. Everything intersecting that orbit will be sandblasted, increasing drag; this will have the greatest effect on the smallest debris, and hopefully anything operational in that orbit will be well enough armored or able to dodge the cloud. The dust deorbits quickly for the same reason as the tiny debris (greater surface area/volume). One of the more metal ideas for space debros handling I've heard.
Increasing surface area will (eventually) de-orbit due to drag.
The wire methods mentioned earlier could possibly offer the option for magnetic / induction drag.
Ion engines are an option, though they're spendy.
Geosync orbit is the tough one. It's much larger, but the sweet spots (equatorial orbits) are relatively scarce.
Mandating methods of clearing critical orbits (for GEO) or deorbiting (for LEO) implemented prior to deployment is probably the more viable option.
Still that will only prevent a dead sat in sitting in a valuable spot for ever, it migh still drift the wrong way and require active sats to do avoidance maneuvers, not to mention the chance of two inactive sats colliding.
There's also the problem of retaining propellants over long periods without experiencing some negative consequence (detonation, unintended firing, volatilisation, etc).
But in general, minimising the special-handling cases would be an improvement.
If not the sun then maybe the earth?
That would be a fun spacewalk.
In comparison, a deorbit burn is usually relatively inexpensive.
For comparison, the fastest bullets go like ~1,500m/s, and they are very very very small.
I don't think we should do either of those, but less mass is always easier to speed up.
Similarly, if a satellite is light enough in low-G to grab and manipulate from a craft that has straddled up along side it, would a single astronaut have enough strength to use his arms to put a satellite on a path that is effectively out of the way? Or could they just chuck it back at the earth so it can burn up on reentry?
edit2: actually now I'm not so sure, I might have had the right number initially. It's either 24k or 32k. Either way it's impractical.
24,000m/s is the difference in speed that the astronaut is already traveling with the speed necessary to get to the sun
Getting to the sun is really hard.
Chucking it back into the atmosphere is much easier, but GP was asking about throwing things into the sun.
But the speed of the baseball you just thrown out will be (ignoring air friction) that of the airplane +/- 40 m/s, assuming you're some super strong thrower.
> if a satellite is light enough in low-G
Microgravity doesn't mean the satellite is light now. It still has the same mass, it's just that you're both in free fall, so it doesn't pull away from you. For the purpose of throwing it, the satellite is just as hard to throw as it would be on the surface of Earth.
But even assuming it weighs as much as a fastball, when you throw it super hard, you'll change its velocity by... 40 m/s at best. Compare that with the orbital speed, which is many kilometers per second (e.g. about 7.6 km/s if you're on ISS). So e.g. instead of going 7.6 km/s, the thrown satellite now goes... 7.56 km/s. Which translates to one end of the orbit dropping by a couple hundred meters. So instead of 408km, it'll now go as low as... 407.5km, or something in that ballpark.
That's the limit of what you can achieve by just tossing things with muscle power.
Something in earth orbit is also orbiting the Sun. The Earth is traveling ~30km/second around the Sun. If you want to fall into the sun, you have to cancel out all that sideways speed.
(I've also had my fair share of high-orbit missions where in the middle of the launch I realized I'm aiming for a prograde orbit, where the contract specified retrograde. Instead of reloading game from launchpad, I just carried on, put my apoapsis at target altitude, and once reaching it, burned off couple hundred m/s of Δv to reverse the orbit's direction.)
(Ignoring smaller effects)
Unfortunately throwing things at kilometers per second by hand is not possible, 1 km/s is just under 2237 mph.
Of course with atmospheric drag for most low orbit satellites things will come down eventually, in which case throwing something the right way could add or subtract from the time it will stay in orbit, but that would be highly dependent on where you started. And LEO is already like 7.2 km/s or about 16,000 mph. Standing on a massive enough satellite using a large stick or like a sling staff would certainly help you get more speed in your throw though. A 100 mph baseball throw really wouldn't be that significant though.
I wish humans were less interested in the noisy, explosive things like engines and rockets, and more into subtlety.