I've been following with interest a couple of articles recently about cleaning up space debris, often (I think, inappropriately) called "space junk".
One proposal was for so-called "janitor robots
" and the other, announced recently, was to deploy gas clouds
to cause space debris to fall out of orbit.
While these clearly address the immediate problem, I think it's a suboptimal solution, principally because it took a lot of energy to get those objects into space, it will take a lot more energy to deploy gas canisters and janitor robots, and there may simply be a better way.
Space scientist Robert Zubrin speaks of a future where automated robots could, far in the future, help colonize the solar system by harvesting raw materials from asteroids and comets. But to me, the potential for the beginning stages of that could begin with unwanted space debris here in Earth orbit.
And, well over a century ago (!) Konstantin Tsiolkovsky proposed the concept of a "space elevator", wherein a counterweight in far Earth orbit would be connected to a tether, upon which robotic climbers could gradually lift things into low earth orbit from the surface.
What if instead, we begin creating an equatorial ring, like on Saturn, except composed of space debris? Doing so would require two sets of robots. "Pitchers" and "catchers" as I call them. Pitchers would grapple onto a hunk of space debris wherever it is, and realign its orbit towards the catcher robots and let go. The catcher would gather the pitched material and set it into the common orbit of all of the objects it's caught. Once enough mass was collected at a given location, you could have the catcher robots assemble them with nets to form a counterweight.
Another benefit to collecting this material in a single location or at least in a single orbit is to enable harvesting by robots that would be produced in the future that have the capability to harvest the raw materials from this orbital ring of spent and disused space junk.
And finally, the space elevator could also benefit from having a counterbalance that would reduce the amount of energy that the climber would have to expend to reach low earth orbit, much like the counterbalance on an elevator means that you can use smaller motors to motivate a terrestrial elevator.
As many physics students learn in high school, there is a lot of potential energy stored up in that junk in space, and energy is one of the most significant costs and burdens to cheaper and more efficient space travel. Which ultimately means that thinking of it as "junk to be disposed of" may be somewhat shortsighted.