How could the space debris in Earth orbit be cleaned up?

I read a few answers that says we don't need to. If you say that to a NASA scientist, he might disagree with you. Yes, space debris are destined to come back on earth and burn in the atmosphere.

But before doing so, they will orbit Earth for quite a while. And they might find on their path something scientists consider useful, like a satellite. And given the speed of space debris, even a tiny tiny debris, such as a screw, will cause some damage to the satellite. Of course, the satellite will damage the screw, but scientists don't care about that.

The amount of space debris is incredibly huge, and it is a big concern for space agencies. They are constantly scanning space in order to detect them. The biggest ones are known, and satellites constantly modify their trajectories to avoid space debris. It is important to try and remove them. And they are trying to find ways.

Several projects are under study. Some suggest to use a tether that would generate an electrical field. Because of Earth's magnetic field, it would slow down the debris, and bring it back on Earth sooner than if only gravity pulled it back.

Another solution is to modify the course of space debris with thrust. A small satellite could come close to bigger space debris and bring them back on Earth so that they can burn in the atmosphere. A solar sail can also be used in the same way.

Alternatively, bombarding debris with ion canon could alter the course of a debris. For smaller debris, other solution exists, such as capturing them in foam.

Many options exists, and the space agencies are currently starting to test them. The best one is not known yet, but cleaning space is starting and soon, we might realise that one way is better than the others. At that time, we will hopefully be able to drastically reduce the amount of junk orbiting Earth.

But yes, it is important. Yes, we need to. Or we might loose several satellites in the future.

In more than half a century of space activities, about 4800 launches have placed some 6000 satellites into orbit. Today, less than a thousand of them are still operational. Imagine the amount of debris orbiting the earth today.

The space debirs cannot be "removed" or "gotten rid of" per se. They can only be "mitigated". The word "mitigation" refers to "the action of reducing the severity, seriousness, or painfulness of something."

Mitigation measures ranges from reducing the current growth of space debris by implementing operation procedures such as choosing orbits with less risk of collision with debris and, in case of a predicted collision risk, maneuvering spacecraft away from the debris path, to prevent the creation of new debris by smart satellite design, considering end-of-life passivation measures and adding end-of-life technologies.

In 1995, NASA was the first space agency in the world to issue a comprehensive set of orbital debris mitigation guidelines. Other countries and organizations have then followed issuing their own orbital debris mitigation guidelines. In 2002, after a multi-year effort, the Inter-Agency Space Debris Coordination Committee (IADC), published the "IADC Space Debris Mitigation Guidelines," a reference document for technical guidelines, designed to mitigate the growth of the orbital debris population. The IADC presented these guidelines to the UNCOPUOS Scientific & Technical Subcommittee (STSC), where they served as a baseline for the "UN Space Debris Mitigation Guidelines," which are a set of high-level principles accepted in June 2007 by the COPUOS and endorsed by the United Nations in January 2008.

Space debris is becoming a significant concern among space agencies.

In the early days when there was practically nothing in orbit, launching your rockets often meant the use of pyrotechnic bolts that separated your rocket stages from each other, opened the shrouds that protected your payloads, and bolts detonated to release your payloads into orbit.

Space is big. So in the early days, the idea of getting hit by something was usually left to worrying about meteors and other natural stuff in space.

After over 60 years and thousands of launch vehicles that have left for space, there's a lot of spent bits and pieces of rockets up there.

How much? To get an idea, visit Stuff in Space and see for yourself.

Go ahead. I'll wait.

There are initiatives, in the planning stages, to remove space junk from low Earth orbit – but nothing concrete.  The subject of space debris is very complicated.  There are more than 22,000 pieces that are 10 cm across or larger and maybe half a million more that are smaller.  Removing debris is complicated both technically and legally.  The technical complications range from the vast amounts of energy needed to maneuver in space and the hazards of grappling an object that might fracture into many smaller objects.  The legal complications are:
  1. Under international law, space debris belongs to the original owner of the object that was launched into space, so it can't be removed without permission.
  2. In order to safely and effectively grapple large objects, their specifications need to be known, and that introduces all kinds of ITAR issues with sharing advanced technologies.
  3. Technology designed to remove debris from orbit could also be used to remove active satellites from orbit, and thus may be seen as a space weapon.
There is an international group called the Inter-Agency Space Debris Coordination Committee that has representatives from eleven different space agencies.  They are tasked with looking into it, but don't have authority to resolve the mentioned legal issues.

As many debris objects as there are, they are still pretty spaced out.  So collecting the debris is difficult.  We can't just send up a spacecraft with a catcher's mitt to scoop up debris, because it would only affect the small amount of volume carved out by the cross sectional area of the catcher's mitt.  It costs a tremendous amount of fuel to change a spacecraft's inclination.  And filling the sky with these garbage scoops would be counterproductive because if just one of them were to hit an object and break apart, it could let loose more debris than it ever could have caught.

Some of the ideas under investigation to remove space debris are:

EDDE - Electro–Dynamic Debris Eliminator:  This is a space vehicle that would be propelled by the Earth's magnetic fields and would use large expendable nets to capture and decelerate large debris objects.

SpaDE – Space Debris Elimination: This would fire bursts of gas from the Earth's surface at objects in space to decelerate them.  For many LEO objects, it is calculated that a 3% deceleration would be sufficient.  Estimates are that it would take about 500 gallons of gasoline per object to power the "air cannon".

Sling-Sat – TAMU Sweeper: This is a project of Texas A&M.  Their idea is to create a small spacecraft that would instead of capturing debris, catch it and immediately propel it away in a plastic collision.  This would be carefully calculated so that the energy of collision would decelerate the debris into a deteriorating orbit and would propel the Sling-Sat on a trajectory to the next piece of debris.

Another option is to use ground based lasers to use light pressure to decelerate objects.  Most estimates say the energy needed to deorbit the debris isn't practical, but it could potentially be used to prevent a predicted collision with an active asset.

One option involves giant aerogel nets.

One of the big concerns is that even if we weren't adding more, over time large pieces hit each other and produce a greater number of small pieces, so the cloud would keep growing.  An analysis from NASA's Orbital Debris Program Office here at JSC predicts that if we could remove just 5 of the largest pieces, each year, we could actually keep the debris threat in check.  62% of the debris is believed to be made up of large Russian rocket upper stages.

Good question, and much more important than most of us realize. My brother was an officer in charge of the "space command" section at Cheyenne Mt. for quite a few years, and tracking objects in orbit was part of what they do. There are literally thousands of debris objects in various orbits and, whenever they collide with anything and become fragmented, it only adds to the mess.
However, "cleaning it up", though it sounds easy enough, is a monumental task. These are very small objects... anything from small specks of metal, plastic and paint, all the way up to hammers and other tools, and spent rocket boosters, etc. They orbit in a HUGE volume of space, and are travelling at the speed that corresponds to their orbital height... typically 17,000 to 20,000 mph. Just locating some of these objects, and keeping track of them, is an enormous task. Actually retrieving them would be titanically expensive. Like trying to find and net every plastic cup, candy wrapper, empty food container, or other piece of trash dropped from every ship that travels on the oceans of the world. The oceans are not as big as the orbital volume of Earth's space, and the objects are certainly not travelling as fast. But the trash in space is in relatively stable orbits that can (for the most part) be calculated with great precision. Trash dropped into the ocean can wind up anywhere, depending on currents, storms, winds, etc.
Not an easy task at all! A lot of time, effort and money required. The best thing we can start with would be to begin by not adding to the problem. We should make every effort to insure that whatever "goes up" does indeed "come down" (unless it was our purpose to leave it up there specifically). And we can certainly start by eliminating some of the bigger debris... dead satellites and larger objects drifting in heavily-used corridors of orbital space. That would probably be a good place to start. But to retrieve every screw, nut, bolt, widget... everything lost over the past fifty years? That is a daunting task, to put it mildly!

So, so so many. Here: Google Patents

People thought of so many ways to deorbit things since that has been a problem (there are patents since the 80s and earlier) and they have been patenting them left and right. Check them out and click on the links to see images (try the pdf):

There are so many, many, many more, including blasting them with lasers, launch them into interplanetary space, launch them to the sun, and so on. Not all of them are realistic or feasible, but that didn't stop people from patenting those ideas.

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