# How do we remove existing space junk from orbit?

There is a metric buttload of junk in orbit, and we seem to be getting closer to the more dangerous part of the Kessler Effect curve. I know that modern satellites, like Starlink, have mechanisms to de-orbit themselves at end of life. But we still have a very large number of objects orbiting. So my question is, how do we deal with removing existing space junk?

Maybe it’s my lack of imagination, but I can’t think of a reasonable way of removing it.

For defunct satellites, I can imagine a vehicle that would attach some form of de-orbiting device, but how many satellites could be de-orbited per vehicle? I suspect one or two per vehicle due to launch weight, orbital mechanics, etc.

More importantly, how do you capture the small debris moving at 17,500 mph? A bolt, nut, or screw moving at this velocity could punch through almost anything you could put in its way trying to catch it (creating more debris). Is there any material that is capable of catching these high velocity debris particles without creating more debris particles? Are there any proposed materials or methods that have a chance of reducing these particles?

J.

What you want is a giant sponge.

Well, the stuff trying to catch space debris is also orbiting at those speeds (or near enough). Like driving down the highway, the other cars are doing 60 mph but so so are you. Your relative motion is low.

Those speeds, but not that velocity. For things at a Cape Canaveral inclination, relative speeds can be as much as 95% of the orbital velocity. For Baikur inclination, it can be 155%.

I was thinking a giant catcher’s mitt.

Is there any sort of material or device that can catch that debris without creating more debris?

J.

If the goal is to collect miscellaneous debris (and not whole satellites) then I think the best you can do is a net made from kevlar and/or carbon fiber. Like a bulletproof vest. Expand the net in orbit and move a little more slowly than stuff in that orbit so it flies into the net. Then de-orbit the net. Not sure how you manage to not catch bigger things you don’t want to catch (like a working satellite).

I am guessing that is easier said than done though.

I recall reading something somewhere once upon a time that suggested using lasers somehow. I googled it and it’s a real concept.

“Those speeds, but not that velocity. For things at a Cape Canaveral inclination, relative speeds can be as much as 95% of the orbital velocity. For Baikur inclination, it can be 155%.”

Can you explain this a little bit more?

J.

It’s easiest to launch things into an orbit with an inclination equal to the latitude of the launch site. So most things launched from Cape Canaveral will be at an inclination of about 28º, meaning that over the course of an orbit, they’ll move from a latitude of 28º north to 28º south. When such a satellite crosses the equator, it’ll have a north-south component of velocity equal to its total velocity times sin(28º). So if an object is at the equator moving from north to south, and collides with another object at the same inclination but moving south to north, their relative speed will be twice that.

The Russian launch site is even further north, so anything launched from there (or launched to be compatible with things launched from there, like the ISS) will have an even greater inclination, and so cross the equator at an even greater angle, and so potentially have higher relative speeds.

There’s been a lot of professional thinking on this topic. And the small stuff is acknowledged to be a real problem. It’s too numerous to spend much money or energy or cleanup equipment lifetime on. Nobody kills ants individually with a BB gun; you have to deal with them en masse somehow. The space broom is about the only idea I’ve read which has much of a chance.

Some fairly efficient ideas for deorbit systems include tethers which induce drag versus the Earth’s magnetic field. It might take years to pull something down, but once the tether is attached or deployed, it’s an increasingly rapid one-way trip into the atmosphere.

A political trap with cleanup systems is that an orbiting garbage collector is exactly the tech needed to capture & perhaps retrieve intact enemy satellites for reverse engineering. Or simply to take them out of service without triggering even more debris as a simple explosive, projectile-based, or laser attack might do.

The fact that various constellations reside in uniform orbits means that e.g. blowing up several GPS satellites will concentrate debris at the altitude and inclination of the GPS constellation. Doing the same to Russia’s GLONASS would likewise concentrate debris where further GLONASS fratricide becomes more likely.

As always, humans are why we can’t have nice things.

Regardless of where the launch occurs I thought it is possible to put whatever it is into any orbit you want.

It’d be crazy to think that only one orbital trajectory was possible based on the launch site.

Granted it may take more fuel and fuss to get the orbit you want but they can do it (can’t they?).

Up to a point yes. The most efficient launch is along the natural trajectory of your launch site. Anything else costs payload, and the more different the trajectory, the more it costs.

In a business where \$10,000 per pound to orbit has been routine, that’s not a parameter to waste unless you’ve got a darn good reason.

“Cost”, in this case, is fundamentally the increased acceleration budget required to support the extra energy that has to be expended to alter the inclination of the orbit at launch (or later, which is also a possibility if the spacecraft is designed with that capability).

More acceleration budget means, at a minimum, more fuel or less payload or tradeoffs in other attributes of the orbit.

Those all factor into the dollars-and-cents cost of a launch, of course, which is where it pinches in the real world.

Of course this has to be on the soundtrack to the documentary:

The precis of Planetes, a manga and anime series is after a exo-atmospheric passenger craft is destroyed by a collision with debris the world government has decreed that commercial enterprises in space must help with cleaning it up. Points are awarded for how difficult or dangerous the item is to salvage or remove and a minimum number of points is needed per year.

Companies are loathe to spend money on this effort so the Space Debris Section of Technora Corporation, where the main characters work, is known as the ‘half section’ because it has half the budget, half the equipment, and half the personnel it needs to be truly effective.

Yeah, while a kevlar or carbon fiber net is a nice idea, is it really feasible? Bulletproof vests can stop handgun and some rifle rounds (which are moving from 1000 FPS to a little over 3000 FPS). Objects in LEO are moving at about 17,500 MPH or 25,666 FPS. Can kevlar or carbon fiber survive a hit with objects moving this fast with so much energy?

I don’t understand orbital mechanics very much, but I just know that it is REALLY WEIRD and counter intuitive. I THINK that if your net is moving slower than the debris, your net will be in a different orbit than the debris, and won’t capture the debris.

Can someone more familiar with orbital mechanics weigh in on this? How would a net or bubble moving slightly slower than debris actually capture that debris? Or in general, how would you maneuver a net or bubble capture debris?

J.

p.s. to Whack-a-Mole: All due respect, and I’m not trying to pick on you. Your suggestions came to my mind, too, and they raised questions that I’d like answers to.

It’s only a little more expensive to launch into a higher inclination (though that’s in relative terms; everything about space is expensive, so usually you just take the inclination you got). But it’s extremely expensive to launch into a lower inclination. Like, the easiest way to do it is to launch out past the Moon. That’s why the US accommodated Russia, rather than the other way around, with the ISS.

And most space junk is at an altitude where it just barely stays up. Orbit slower than that, and your net is coming back down very quickly. But you don’t need to do that, because nearly everything up there has some relative velocity anyway.