From almost the first moment that man started traveling beyond Earth's atmosphere, we've been leaving behind all sorts of debris in space. Not only is it wasteful, but space junk can be dangerous as well - to satellites, to space stations, and when some of it plummets back to Earth, to human life on the ground. But there is no shortage of concepts for cleaning up the junk we've left behind in orbit, even if some of them seem far-fetched. Here's an overview of some of the ideas being proposed for cleaning up space debris.
1. Giant LasersUsing high-powered pulsed lasers based on Earth to create plasma jets on space debris could cause them to slow down slightly and to then re-enter and either burn up in the atmosphere or fall into the oceans. "The method is called Laser Orbital Debris Removal (LODR) and it wouldn't require new technology to be developed - it would use laser technology that has been around for 15 years. It would be relatively cheap, and readily available." The biggest hitch, other than adding more litter to the oceans, is the estimated $1 million per object price tag.
2. Space Balloons
The Gossamer Orbit Lowering Device, or GOLD system, uses an ultra-thin balloon (thinner than a plastic sandwich bag), which is inflated with gas to the size of a football field and then attached to large pieces of space debris. The GOLD balloon will increase the drag of objects enough so that the space junk will enter the earth's atmosphere and burn up. If the system works, it could speed up the re-entry of some objects from a couple hundred years to just a few months.
3. Self-Destructing Janitor Satellites
Swiss researchers at the Federal Institute of Technology have devised a small satellite, called CleanSpace One, which could find and then grab onto space junk with jellyfish-like tentacles. The device would then plummet back towards Earth, where both the satellite and the space debris would be destroyed during the heat and friction of re-entry.
4. Wall of Water
Another idea for cleaning up space junk, from James Hollopeter of GIT Satellite, is to launch rockets full of water into space. The rockets would release their payload to create a wall of water that orbiting junk would bump into, slow down, and fall out of orbit. The Ballistic Orbital Removal System is said to be able to be put into action inexpensively, by launching water on decommissioned missiles.
5. Space Pods
Russia's space corporation, Energia, is planning to build a space pod to knock junk out of orbit and back down to earth. The pod is said to use a nuclear power core to keep it fueled for about 15 years as it orbits the earth, knocking defunct satellites out of orbit. The debris would either burn up in the atmosphere or drop into the ocean. A company representative claims that they could clean up the space around Earth in just ten years, by collecting around 600 dead satellites (all on the same geosynchronous orbit) and them sinking them into the ocean.
6. Tungsten Microdust
In theory, tons of tungsten microdust put into low earth orbit, on a trajectory opposite that of the targeted space junk, would be enough to slow smaller space debris (with dimensions under 10 cm). The slowed debris would then decay into a lower orbit, where it could be expected to fall into earth's atmosphere within a couple of decades, not the hundreds of years which the debris could remain in orbit at their current altitudes. The biggest problem with this idea is the possible health issue of tungsten entering the atmosphere - tungsten compounds have been associated with stillbirths and abnormal musculoskeletal development in some studies.
7. Space Garbage Trucks
The US Defense Advanced Research Project Agency (DARPA) is investing in the Electrodynamic Debris Eliminator, or EDDE, a space "garbage truck" equipped with 200 giant nets which could be extended out to scoop up space garbage. The EDDE could then either fling the garbage back to Earth to land in the oceans, or push the objects into a closer orbit, which would keep them out of the way of current satellites until they decay and fall back to Earth.
8. Recycling Satellites
Instead of just trashing space debris, some dead satellites could be "mined" by other satellites for useable components. DARPA's Phoenix program could create new technology to enable harvesting of some valuable components from satellites in so-called "graveyard" orbits. The program would work to devise nanosatellites that would be cheaper to launch, and that could essentially complete their own construction by latching onto an existing satellite in the graveyard orbit and using the parts it needs.
9. Sticky Booms
Altius Space Machines is currently developing a robotic arm system it calls a "sticky boom", which can extend up to 100 meters, and uses electroadhesion to induce electrostatic charges onto any material (metal, plastics, glass, even asteroids) it comes into contact with, and then clamp onto the object because of the difference in charges. The sticky boom can attach to any space object, even if it was not designed to be grappled by a robotic arm. The sticky boom could be used to latch onto space debris for disposal.
These space junk cleanup concepts could potentially help to clear some of the debris which is currently littering the area around Earth, but many of them still have one major drawback - they tend to focus on getting the junk to come back to Earth to land in our oceans, which have enough problems without the added debris. We're still waiting for a decent solution to space junk that not only cleans up the debris, but which also disposes of it in a mindful and environmentally friendly way.