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There are a few companies interested in manufacturing (mostly additive) in space. Let's say that by some miracle some company comes up with a space station that is capable of sending out service satellites to capture defunct space debris and bring it back to the "station" where the debris can be melted down and 3D printed (ignore the complications of printing metal for now).

Does this sound even remotely possible?

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  • $\begingroup$ I wonder what kind of 3D end-products do you have in mind? Why not just compacting these debris and send them to burn in the atmosphere (or send them to a graveyard orbit)? $\endgroup$
    – Ng Ph
    Aug 13 '21 at 17:24
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    $\begingroup$ There is also the pesky notion that stuff out there has owners even though it is junk. You'll need to get permission to recycle it. $\endgroup$
    – Rodo
    Aug 13 '21 at 17:58
  • $\begingroup$ @Rodo, why "pesky"? If the rule is that states are liable for "stuff" they put "out there", it is normal that they retain ownership. In fact, they retain ownership even when the stuff falls on your backyard (and that's why you can ask them for compensation, if you suffer damages). $\endgroup$
    – Ng Ph
    Aug 13 '21 at 21:11
  • $\begingroup$ @Rodo that would depend on whether the material is classified as flotsam or jetsam. $\endgroup$
    – DrMcCleod
    Aug 16 '21 at 9:11
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No doubt this is possible, but it is not practical. The main problem being the vast array of different orbits available and the high energy cost to move between many of them. In most cases it would be far easier to launch a new item than to attempt to move something from one altitude, eccentricity, inclination and right ascension to another in many cases. https://www.narom.no/undervisningsressurser/sarepta/rocket-theory/satellite-orbits/introduction-of-the-six-basic-parameters-describing-satellite-orbits/

For example another questioner asked if Starship could be used to return Falcon 9 second stages back to Earth for reuse. They probably could but it would not be remotely practical. This is because the Falcon 9 second stage is often left stranded in a high energy Geostationary transfer orbit and in order to reach it Starship would have to be re-tanked in orbit first.

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    $\begingroup$ Moving from a geostationary-transfer orbit to a circular one is utterly impractical, yes. But moving stuff between, say, two geostationary orbits could actually be much cheaper than sending new stuff from Earth. $\endgroup$ Aug 14 '21 at 15:43
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    $\begingroup$ I would be much more practical if you didn't have to lift propellants from Earth. Say you use a solar-powered ion engine that scavenges its reaction mass from the stuff to be recycled. $\endgroup$
    – jamesqf
    Aug 14 '21 at 18:27
  • $\begingroup$ Or bring fuel from the moon or asteroids. This could make large plane changes more economical $\endgroup$
    – Innovine
    Aug 16 '21 at 15:21
  • $\begingroup$ trouble with the Moon is the extra cost of landing and launching really eats into the economics and asteroids are likely to present time issues. Neither are happening any time soon. $\endgroup$
    – Slarty
    Aug 17 '21 at 8:56
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The previous answers are wrong. Moving stuff between two reasonably similar orbits is actually much less energy-intensive than launching up the same mass right to the intended orbit. And indeed any LEO has lots of kinetic energy that can be used to get to a higher orbit.

The real question is whether the difficulties in detail will outweigh this advantage. In most cases they probably will:

  • Before you can move the debris, you need to rendezvous with it. Capturing an object that's not explicitly designed for it, and that may be damaged too, is difficult and risky.
  • The individual pieces you can capture mostly won't be so big that it would really be worthwhile. Especially at the development stage where you could get use out of this stuff, you'll likely anyway be launching at an exponential rate, so the amount of potentially recycleable material is tiny compared to what you need to get up from Earth anyway.
  • The material itself you could obtain would be much harder to use than fresh stuff. You won't get raw material but near-inseparable composites. For the time being, processing anything in space will be orders of magnitude more difficult than it would be on Earth. So I don't think it's feasible to build anything nontrivial from the old parts.

The only thing they could perhaps be useful for is radiation shielding.

The most realistic way the gathering could be implemented is probably to send out small robotic tugs with ion drives.

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  • $\begingroup$ The previous answers did not deal with two reasonably similar orbits. Your very special case is not the whole truth. If two LEOs of different height should be used, they should have the same inclination for a low energy transfer. Changing only the inclination and not the height needs a lot of energy. $\endgroup$
    – Uwe
    Aug 14 '21 at 16:18
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    $\begingroup$ But there are plenty of objects on orbits with reasonably similar inclination. To stay with your analogy: yes, it's nonsense to use junk cars from the other side of the Earth – because there's a perfectly adequate junk yard in the next town! $\endgroup$ Aug 14 '21 at 16:29
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    $\begingroup$ The energy and delta-V requirements would be substantially influenced by how long one was willing to wait for orbits to line up. Non-geosynchronous satellites continuously receive delta-V from tidal forces, and the rate at which delta-V is received depends on altitude. $\endgroup$
    – supercat
    Aug 15 '21 at 20:02
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If somebody wants to build new cars from junk cars as raw material, would he use junk cars from the other side of the Earth at maximum distance? Would he transport every junk car one by one using a trailer coupled to his SUV? Would he take all the gasoline needed for the whole trip with him loaded on another trailer?

If you think this method to get the raw material for a new car does not make sense, recycling space debris as raw material for new satellites makes much less sense.

Transport from one orbit to another orbit at different height and inclination and back is extremely expensive and would need a huge amount of fuel.

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    $\begingroup$ You demonstrated that the collecting part of the process is costly. But may be in the future people will be asked to collect the wastes that they have put there (or pay somebody to do it). Hence the follow-on questions: what do we do with the "junk", once collected? Should we start right now, looking for engineering processes so that the rockets and satellites are re-cycable in-orbit? Food for thoughts ... $\endgroup$
    – Ng Ph
    Aug 14 '21 at 8:22
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I would sell the idea of space junk as a service performed to remove a hazard to orbital navigation more than as a source of material for large scale manufacturing. The presence of junk in orbit is a big constraint of placing more objects in orbit. Removal might be sold as a service. Although, both spare parts and materials would be a secondary source of income from your business.

Another potential source of income from your space junk retrieval business might be the recovery of "space antiquities". Imagine what some billionaire might pay for a satellite from the early years of space exploration or some piece of a space shuttle or a defunct Soviet era satellite with "provenance".

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