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Bi-Directional Plasma Thrusters for Space Debris Removal (nature.com)
30 points by ArtWomb 73 days ago | hide | past | web | favorite | 22 comments

Is it realistic to presume that space debris orbiting around the earth will only ever get worse, or will it effectively remain the same to some degree of consistency?

Or is it more of a thing that it only becomes more of a noticeable problem for us as humans when we are affected. Meaning that the only reason we have a problem with it now as opposed to some previous timespan is that we are sending more and more objects/satellites/etc into orbit and they are being damaged/destroyed/affected, so we therefore write about it and try and come up with ways to stop it?

Most of the debris in orbit is a result of 2 events, one of which was a purposeful action of the Chinese government. So if humanity can refrain from blowing up satellites, or at least keep from blowing them up in the stupid way the Chinese did, it should remain manageable.

Of course, some of the most difficult to track debris was put up there in the name of science- the Telford needles, pieces of tether, and shreds of solar sails. If the big net experiment from a couple of weeks ago had gone awry, we'd have another difficult to track fabric-like bit of junk shredding itself into smaller yet still dangerous pieces up there.

Was a bit sceptical at first but this seems fairly correct. There's been numerous collision events, only one stands out as intentional and of greater magnitude than all the rest. I do wonder how future generations will judge such actions given the difficulty of clean up and general world consensus to not militarise space.


Yes, it's a combination of the fact we are living with increased dependence upon space based systems for weather, navigation, communication, defense, etc. And the enormous cost in production and deployment. Tracking space junk and issuing course corrections to orbiting satellites won't scale. As demand for low earth orbit real estate surely will increase with the coming New Space era of zero-g factories, space tourism and myriad other ventures. Clearing space debris is vital to continued exploration and represents an enormous opportunity, not to mention an engaging engineering challenge ;)

The linked bi-directional plasma solution seems really elegant to me. And is feasible even for objects several meters in size. With fewer possible mishaps than say laser ablation.

More detail here:

The quest To Conquer Earth's Space Junk Problem


> Is it realistic to presume that space debris orbiting around the earth will only ever get worse, or will it effectively remain the same to some degree of consistency?

Debris in high orbits isn't a big issue; there's too much space. Debris in low orbits falls out of the sky on a timescale of ~decades, thanks to aerobraking. So it should be constant, given a constant inflow of debris...

However, that is only true so long as collisions remain rare. Once there's too much debris, Kessler syndrome will cause it to 'breed' and close the orbitals for decades.

The above also doesn't account for super-popular high orbits, i.e. geosynchronous. A sufficient amount of debris in that orbit could close off that one for millennia (or until cleaned), but at least there are alternatives.

Geosync orbits have a de-orbit requirement (at least US operations do). So they have to keep enough fuel to go into a higher orbit after their lifetime. This wasn't always the case but it is now.

Also Geo orbit (while popular) is only useful if you get a fairly large degree of it all to yourself. My current understanding (correct me if I'm wrong) is that most satellites operate at fairly large distances from each other in Geo about 0.5 degrees apart is normal. Mostly because the antennas sending signals from have a wide beam at the point they hit the satellite and affect adjacent satellites. So they have to distance the Adjacent satellites far enough apart so as to be effective in communications. This isn't a problem for different frequencies, so you might stack a K and C band satellite on top of each other. But most of the Geo beasts have full capacity for the spectrum they are legally allowed to use.

Also, I'm speaking strictly about COMM satellites. I haven't done any practical application on anything else.

The space debris around Earth is bad due to several reasons. One is a legacy of disinterest for the problem fueled by a greater concern for the fundamental difficulties of space travel. Consider a stereotypical pseudo case study for a space mission in the '60s or '70s or thereabouts. First you have the launch, each stage is festooned with pyrotechnic actuators, cords, blankets, yo-yo despin bits and bobs, and so forth. Every launch deposits a shower of debris into orbit, which orbit depending on the orbit of the payload, some of them potentially long lived. Bolt heads, wires, paint flecks, etc.

The final stage boosts the payload into its orbit then separates. Of necessity the final stage tends to be in a very similar orbit to the final payload, except weighing much more. For example, most sightings of the Sputnik spacecraft were actually sightings of the much brighter upper stage tagging along in orbit behind it. Ah but the stage is not necessarily done doing stuff yet, just not stuff it was intentionally designed to do. The stage will often have leftover propellant in it, and it was common to simply abandon the stage in place (on orbit) after its work was done. As a consequences, a lot of upper stages blew up on orbit after delivering payloads, creating yet another shower of debris into Earth orbit.

And finally you have the payload itself, which was very commonly simply abandoned in place once it became derelict.

Multiply all of that by the low operational lifespan of early satellites coupled with a high replacement cadence and you have a reason why Earth orbit got crudded up with debris in a short window of time.

Today we are considerably more sensible about the problems of space debris so our launches are much cleaner. Instead of every launch creating a new mess in orbit every launch generally just inserts 1 or 2 pieces of large, easily trackable components (the payload and the upper stage, if it wasn't deorbited). For LEO launches the upper stage is typically deorbited immediately, for GTO launches the upper stage typically takes a handful of years to orbitally decay and re-enter.

For this reason orbital debris has typically been on a flat or decreasing track over time during any given year. However, there are a few notable events in the past which have generated exceptional amounts of debris. One example is Project West Ford, which put thousands of tiny needles into orbit, which should have re-entered promptly except that some of the needles clumped up, leading them to have long-term stable orbits (which will last hundreds of years most likely), polluting some significant chunks of Earth orbit. Then you have the Iridium/Kosmos-2251 collision and the Chinese ASAT test, both of which injected huge quantities of debris into orbit.

In general, all of these things can be cleaned up given application of modest resources, and the fact that we are no longer polluting Earth orbit with debris as rapidly as we once were means that we should be able to sustain far higher levels of space activity with far lower risks due to orbital debris than today.

Something I proposed and sent to the experts many years ago; back then I was thinking of opposing ion rather than plasma engines of course. Plasma wasn't a thing, then.

A point they've dropped from my proposal is that used on a spinning target you can de-spin it. (Even if it's spinning along more than one axis in fact, with intermittent thrust.) This is especially useful to capture, move, and then utilize asteriods, say. Or as a way to stabilize the target (such as an asteroid), so that both engines can be joined to the target to move it. See "jacknife" below.

Very useful for cleaning debris from orbit.

A few years ago, I realized that what you want is a "jackknife" implementation with a hinge between the two engines that allows you to use both thrusters to move to and from the objects you want to move. Since no-one had picked up the original idea (except as modified to use gravity vs one engine), I made no attempt to publicize that refinement to the idea.

Just out of curiosity, why didn't you apply for a patent?

Ill and therefore poor. Not the only famous idea I could have patented. I could take out a couple of hundred patents now, still, if I had the money.

Given the rate at which our patent offices hand them out, there's no doubt any one of us could take out a couple of hundred patents if we had the disposable money to apply for them.

True! But I did mean wholly legitimate patents of useful novel ideas.

Ooh, what about a laser on the space side of the debris that heats it, causing the release of gases that propel it towards earth? You would have to be able dynamically re-target the debris for uniform acceleration while also pulsing the laser if the debris is spinning, but it would probably work.

soure: I can't even do basic math, but maybe someone smart will think this is an interesting idea

It might be better to just shine a bright laser on it for an extended period of time and let light pressure do the job.

Side not, you would do this to the 'front' of the satellite as it orbits - the bit facing in the direction of travel. This would slow it down and make it fall into progressively lower orbits until atmospheric braking took over.

Somewhat inspired by the Japanese robots bouncing around on the Hayabusa2 mission ... I think it'd be nice to be able to 'push off' against the debris satellite, to both decelerate it whilst also gaining orbital velocity for the clean-up satellite to go hunt down another target.

If you push off against it to gain velocity, you'll fly away from it very quickly and not spend long enough pushing it to meaningfully change it's orbit.

It might be concievable to bounce lased light back and forth for a while and transfer momentum that way.

Much of the debris is not even that large.

Is anyone else thinking of "the Kzinti lesson" from the Known Space books?

The idea of waste or debris in space is simply wrong.

It's a bit of flatlander nonsense that should not be brought off the surface. I was shocked as hell when I found out astronauts vent trash and waste.

"Come, let us reason together."

There are not a lot of atoms in space, by definition, compared to terrestrial conditions. (Okay, technically all atoms are in space. You know what I mean. ;-P ) So, if you have some atoms together in space already it's just stupid to disperse them into small bundles and then lose track of their orbit. (You can't throw things away in space, you can only lose track of them. They'll be back.)

It takes a lot of energy to get a bunch of atoms to orbit from the surface. It's wasteful to discard "waste"! (Say it with me, "No waste in space!") Literally, in space, matter is only "waste" because you let go of it and stopped paying attention to it. It's still useful, just not to you right now. Even if you're sure you'll never have a use for it, it's criminally irresponsible to "throw away" matter in space. It's like firing a gun into the air: that bullet is coming down somewhere... At the very least bundle it up and tag it with a radar reflector or something.

In conclusion, space is big and empty and curved, atoms are rare, important, useful, and expensive to bring with you. Keep them nearby and on stable orbits. That way you don't have to waste energy collecting them again and they aren't rattling around forming a collision lottery in LEO.

No waste in space.

- - - -

Now then, as a bit of a tangent, are you familiar with the "spittlebug", Cercopoidea? Their nymphs form nests of bubbles that look like little blobs of spittle. I say this is the correct design for space vehicles and stations. Spittlebug nest. Not metal can. Cheap, simple, ridiculously easy construction methods, durable, self-repairing, reusable, flexible, etc... I'm sure we could make materials that permitted different kinds of bubble, for e.g. storage, blocking radiation, absorbing collision energy, etc...

So, build your space stations out of bubbles. If you do it right you can collect debris for free. (Hint: you have to intersperse threads with your bubbles and have the right kinds of glue and stick'um. It's all down to materials science at this point, the spittlebug design doesn't really have any other constraints. You could make a space vehicle that "landed" by simply crashing. Density of the atmosphere and the vehicle would determine velocity at touch down. Or, you just make the bubble nest really big. Like 10K diameter. Then when you "crash" your core ship (which actually might be a metal can) settles to the ground through ~5k of bubblewrap.

The space stations we've built have all been in LEO. The ISS would deorbit in less than two years without periodic boosts. As such, no nearby orbit can be considered stable. The fuel required for boost is proportional to its mass. So it's quite reasonable for space programs to cast of 'dead weight' that doesn't contribute to the mission of the space station.

The number one use of atoms in space is to generate delta-v. Sure the ISS could ionize it's waste and use the thrust to maintain it's orbit, but collecting other waste would require delta-v or impart unwanted delta-v (as with the atmosphere)

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