How to Effectively Collect and Recycle Space Junk?
The Question
What would be an efficient and relatively low-cost solution for collecting and recycling of space junk?
The most important criterion of effectiveness is the ability to remove even small pieces of junk from the orbit and then put them to good use. Small is on the scale of millimetres.
Deorbiting should be avoided since it is 1) potentially dangerous for surface installations especially without the protection of an atmosphere, 2) wasteful (unnecessary damage on impact and burning in the atmosphere once terraforming progresses to advanced stages).
Context
A small group of colonists arrives at a moon of a gas giant with a plan to terraform it and build a new life for the generations to come. They aspire to build a sustainable and environment-friendly civilisation that in the future will span over the star system and perhaps even extend its reach to nearby stars.
They start a big-scale mining operation in the nearby asteroid belt and other gas giant moons. Other on-going projects are development and building artificial magnetic shields and a satellite network to monitor the moon and coordinate operations. The colony ship was never meant to land, so it stays in the orbit. Smaller vessels are used to transport people and materials to a tiny domed (and partially underground) installation on the surface. The space traffic is not overwhelming, yet. Accidents are very rare but still happen.
The moon originally does not have any debris or other junk nearby. The colonists intend to keep things neat and clean forever. Therefore, they want to put in place a system of collection and recycling for the space junk. They believe that it would effectively lower the risks of accidents in the future when the traffic is projected to increase substantially. They also do not want to repeat the mistakes of their own Earth and take a route of 'irresponsible mismanagement of resources' that almost killed the planet.
Deorbiting and burning in atmosphere bigger pieces of debris is not a valid option since there is no atmosphere yet. Moreover, the colonists want to reuse the materials and technology. The Chief Engineer is a neat freak, so he insists on collecting and processing even the tiniest pieces of debris. His team is not sure it is possible to achieve his standards of sparkling-clean space, but promise to do their best.
Technological level
The colonists have access to the following technologies:
- fully automated and robotised asteroid mining;
- space travel at 1/10 of the speed of light;
- terraforming technologies (however, only one project has been completed successfully by the time of their departure);
- genetic engineering;
- suspended animation.
Technologies that are envisioned by scientists of today but cannot be built because of technical difficulties (materials, money, political will) are fine. However, something like magic space vacuum cleaner is not possible unless it can be explained by existing science.
Real-life Proposals
There are some real proposals for my problem. However, I am not satisfied with them because they mainly suggest cleaning the orbit by burning the debris.
An approach and capture system "“ a so-called "Pac-Man" solution.
Credit: 2015 EPFL/Jamani Caillet.
Originally published on Space.com
This system uses a net cone to capture debris as small as 10x10 cm (4x4 in). It can be launched from orbit and relies on optical scanners to find and capture junk.
The downside is that it is meant to deorbit junk and burn with it in the atmosphere. It is very wasteful. Also, I am not sure if all debris can be easily seen. Moreover, the net design does not allow capturing of smaller pieces.
This programme is developed by the US Department of Defense to scavenge parts of satellites (such as dishes) and reuse them. Again, this does not help with small pieces and 'useless' junk that cannot be used as parts for new equipment. It is still a much better idea than burning things.
Other approaches include towing junk to other planets (like Mars) to some kind of a recycling facility, using nets and harpoons to capture debris, or just vapourising it with lasers.
This question is not a duplicate of previous questions related to Kessler Syndrome or space debris. My focus is on recycling rather than clearing the orbit. It is also important for me to avoid deorbiting.
This post was sourced from https://worldbuilding.stackexchange.com/q/96930. It is licensed under CC BY-SA 3.0.
1 answer
I propose a double light web, and a (quite distant) robotic 'catcher' grid.
Things in orbit move in nice predictable orbits, at least in the short term, and are only slightly affected by the gravitation of other objects in orbit.
One Light web:
What we want is a pair of bright lasers (not powerful, we don't want them to damage anything) with some hi-res video cameras. They sweep a plane of a large area. If they hit anything, the reflection is picked up as a flash by the video camera. With a few cameras, we can triangulate where exactly in the plane the object appeared.
Another Light web.
This does exactly the same thing, in another plane a few yards from the first, and parallel to it. The line from Plane 1 to Plane 2 gives you the trajectory of the space junk passing through the planes. The time between penetration of Plane 1 and Plane 2 gives you the speed of the object on that trajectory. At the speed of light, this can be communicated 1000 miles away to a grid of garbage cans, spaced perhaps dozens of yards apart. Exactly when and where the space junk will reach the grid of garbage cans can be computed, and the garbage can closest to where the space junk will be uses retro rockets to put itself in the path, catch it, and return to its original position.
All of that can be roboticized.
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