Author Topic: Orbital Debris Cleanup - how to?  (Read 13167 times)

Offline sevenperforce

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Re: Orbital Debris Cleanup - how to?
« Reply #20 on: 04/02/2016 02:50 PM »
Laser ablation would work well enough if the debris had a suitable surface. But using a cold gas thruster and an extremely close pass to drag and deorbit debris is a pretty good idea. I like it.

Offline ChrisWilson68

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Re: Orbital Debris Cleanup - how to?
« Reply #21 on: 04/02/2016 04:16 PM »
* You might start by saying "the mass of satelites and counterrotating material is equal, so if it hits a 1 ton satellite it has probably already encountered 1 ton of counterrotating material (..which would have slowed a nut or bolt out of orbit LONG ago)

There are lots of flawed assumptions here, but I'll just point out this one for now.  Even if the gas stayed in the same orbit (it won't), this claim is false.  If a small piece of space debris hits a 1 ton satellite, you can't expect it to have already enountered 1 ton of counterrotating material.  You can expect it to have enountered whatever portion of the 1 ton satellite is in the cross-section of the debris that hits it.  For example, suppose it hits a spherical piece of debris with a 1 inch diameter.  Then the amount of counterrotating material you should expect it to have hit is the amount of the satellite in a 1-inch diameter hole through the satellite at the point of impact.  That is far less than 1 ton.

Any untargeted use of gas is a complete non-starter.  As others have pointed out, gas disperses far too quickly to do anything useful.

The only thing mentioned in this thread at all that has even the slightest hope of working is targeting an individual piece of debris and expending gas directly into its path immediately before the debris arrives.

And all talk of other debris-removal techniques is off-topic for this thread.  There are other threads for those other techniques.  Please take those discussions there.  This thread is only for discussing using gas to remove debris.

Offline ChrisWilson68

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Re: Orbital Debris Cleanup - how to?
« Reply #22 on: 04/02/2016 04:29 PM »
While targeting an individual piece of debris and expelling gas in its path immediately before it arrives would slow the piece down, it's a terribly inefficient way to do it.  Consider a 1-inch diameter piece of junk.  How much gas are you going to expel in its path?  If you expel only enough that it stays in a 1-inch diameter ball, then all of the gas's momentum will be used to affect the path of the junk.  But the gas will be far less dense than the debris and of equal size, so it will have barely any effect -- certainly not enough to deorbit it.  If you want to have any significant effect on the orbit, you need a cloud of gas that is both huge and dense, so that the mass the piece of junk hits is a significant fraction of its own mass.  But that necessarily means the junk misses most of the mass expelled.  For example, if you want the debris to hit a volume of gas 10 times its own volume, you need a sphere of gas 10 times the diameter of the object.  That means the sphere of gas will have 1,000 times the total volume of the object, so only 1% of the mass of the gas will be encountered by the object.

This is a very, very, mass-inefficient way to do it, and also requires absurdly tight tolerances -- the gas has to be released at extremely high density a tiny fraction of a second before the object arrives and must be within inches of the right position.

Could it be done?  It would be very, very difficult and inefficient, but it could probably be done.  Is it a good idea?  Definitely not.  There are far better solutions.

Offline mikelepage

Re: Orbital Debris Cleanup - how to?
« Reply #23 on: 04/03/2016 05:10 AM »
While targeting an individual piece of debris and expelling gas in its path immediately before it arrives would slow the piece down, it's a terribly inefficient way to do it.  Consider a 1-inch diameter piece of junk.  How much gas are you going to expel in its path?  If you expel only enough that it stays in a 1-inch diameter ball, then all of the gas's momentum will be used to affect the path of the junk.  But the gas will be far less dense than the debris and of equal size, so it will have barely any effect -- certainly not enough to deorbit it.  If you want to have any significant effect on the orbit, you need a cloud of gas that is both huge and dense, so that the mass the piece of junk hits is a significant fraction of its own mass.  But that necessarily means the junk misses most of the mass expelled.  For example, if you want the debris to hit a volume of gas 10 times its own volume, you need a sphere of gas 10 times the diameter of the object.  That means the sphere of gas will have 1,000 times the total volume of the object, so only 1% of the mass of the gas will be encountered by the object.

This is a very, very, mass-inefficient way to do it, and also requires absurdly tight tolerances -- the gas has to be released at extremely high density a tiny fraction of a second before the object arrives and must be within inches of the right position.

Could it be done?  It would be very, very difficult and inefficient, but it could probably be done.  Is it a good idea?  Definitely not.  There are far better solutions.

Well firstly, I'm curious what you think the "better" solutions are? I've not yet seen any I consider "good".

Secondly, all your points are fair, but you are missing the main advantage of the idea as a solution to two conflicting needs:

1) Each piece of debris needs to be targeted individually, probably from relatively close range.
2) It is absurdly inefficient to have any effector craft match velocity with each piece of debris.

If the effector craft isn't matching velocity (the core of my idea above), that means contact velocities remain in the km/s range - and so we need a way to impart velocity on junk at that velocity, without generating more space debris... anything bigger than gas molecules at that velocity is going to generate debris.

Unless... (I could edit this down but I figure I'll let you see how my train of thought went)...

Unless you use something that will sublimate into gas in a vacuum.  That will be massive when the contact occurs, but which won't generate debris because it evaporates following the impact. 

What if you had a craft going along in a standard low inclination orbit as above, setting up rendezvous with junk where it arrives at the point moments before the space junk, but instead of just nitrogen gas, your cold-gas thruster powers an air-cannon which lobs chunks of dry ice (frozen CO2) at the debris?  Maybe you could even craft the "snowball" into a specific "cup" shape to cut down on any shrapnel that breaks away from the junk.

Sure, the accuracy of the snowball air cannon ;)  would have to be spectacular, but if the US military can bullseye one missile with another missile, I'm sure it must be possible, yeah?  Use your lasers not to ablate, but to do fine targeting, use secondary CGS or reaction wheels to adjust the aim of your cannon.  Your range is probably good for 5-10km before your snowball evaporates...

Come to think of it, I just conceptualised a perfect anti-sattelite weapon :P

EDIT: actually no, hitting anything bigger than a certain size with this would just generate more debris, but I think this would be good for small debris.
« Last Edit: 04/03/2016 05:20 AM by mikelepage »

Offline ChrisWilson68

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Re: Orbital Debris Cleanup - how to?
« Reply #24 on: 04/03/2016 09:29 AM »
Could it be done?  It would be very, very difficult and inefficient, but it could probably be done.  Is it a good idea?  Definitely not.  There are far better solutions.

Well firstly, I'm curious what you think the "better" solutions are? I've not yet seen any I consider "good".

One better solution: launch a huge mass of micro satellites to a particular orbit.  The micro satellites have solar-electric propulsion and a grapple.  Each of the thousands of micro sats targets a piece of debris that's in a somewhat close orbit.  It grabs it and de-orbits it.  Repeat for different orbital planes.

Does it require technology development?  Yes, definitely.  But so does a solution that does ultra-precise gas distribution.

I agree your snowball throwing idea is an improvement over the gas idea, but it's not what the thread is about and not what I was responding to.  I was responding to the original idea of the thread, which was specifically to use gas.  Gas is a bad idea for space junk mitigation.


Online KelvinZero

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Re: Orbital Debris Cleanup - how to?
« Reply #25 on: 04/03/2016 10:26 AM »
* You might start by saying "the mass of satelites and counterrotating material is equal, so if it hits a 1 ton satellite it has probably already encountered 1 ton of counterrotating material (..which would have slowed a nut or bolt out of orbit LONG ago)
There are lots of flawed assumptions here, but I'll just point out this one for now.  Even if the gas stayed in the same orbit (it won't), this claim is false.  If a small piece of space debris hits a 1 ton satellite, you can't expect it to have already enountered 1 ton of counterrotating material.  You can expect it to have enountered whatever portion of the 1 ton satellite is in the cross-section of the debris that hits it.
Um.. you might be right. I will think about that again.

However, if you are correct that would still be PLENTY of mass to have removed the object from orbit wouldn't it?

We are talking about small objects, say the size of a thumbnail that it is not practical to hunt down individually but are still large enough to be dangerous. Surely a thumbnailed or smaller object would encounter at least around its own mass in space-station, satellite or astronaut, considering cross-section alone. If it had previously hit its own mass in counterrotating material wouldn't it have dropped out of orbit long ago?

I used the word 'material' to avoid discussing the qualities of any particular gas or particle. Dispersing is fine with me because the debris in orbit is also dispersed. Clearly these dangerous-sized particles can stay in orbit a long time. The question is if non-dangerous sized particles can stay in orbit a useful time.

--- edit ---
Might have just spotted a flaw in my statistical argument. The time for a particular piece of debris to hit a satellite might be huge, eg many thousands of years. We only get hits because there are thousands of them. It is not too surprising if in many thousands of years they sweep out their own mass in super diffuse counterrotating material and are disorbited, but none of the collisons today or in the near future could possibly have had time to have swept out that much material.. Im not sure if the flaw means it would not work at all, because we are selecting for debris which specifically have not had sufficient time, or that it would take many thousands of years to reach a useful equilibrium where this strategy pays off.
« Last Edit: 04/03/2016 11:52 AM by KelvinZero »

Offline savuporo

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Re: Orbital Debris Cleanup - how to?
« Reply #26 on: 04/03/2016 05:11 PM »
Well firstly, I'm curious what you think the "better" solutions are? I've not yet seen any I consider "good".

Always a good idea to look at what is actually being worked on, first.

http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/Technologies_for_space_debris_remediation


https://en.wikipedia.org/wiki/E.Deorbit
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Offline OlegSerov

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Re: Orbital Debris Cleanup - how to?
« Reply #27 on: 04/03/2016 07:44 PM »
Well firstly, I'm curious what you think the "better" solutions are? I've not yet seen any I consider "good".

Always a good idea to look at what is actually being worked on, first.

http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/Technologies_for_space_debris_remediation


https://en.wikipedia.org/wiki/E.Deorbit

I do not see here a better solution to remove small-size space junk.

Offline savuporo

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Re: Orbital Debris Cleanup - how to?
« Reply #28 on: 04/03/2016 07:49 PM »
Well firstly, I'm curious what you think the "better" solutions are? I've not yet seen any I consider "good".

Always a good idea to look at what is actually being worked on, first.

http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/Technologies_for_space_debris_remediation


https://en.wikipedia.org/wiki/E.Deorbit

I do not see here a better solution to remove small-size space junk.

Because realistic solutions for tackling that problem are at very early technology development stage and not fully funded initiatives yet. Such as

http://www.spacesafetymagazine.com/space-debris/debris-removal/electrodynamic-debris-eliminator-receives-funding/
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Online Lar

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Re: Orbital Debris Cleanup - how to?
« Reply #29 on: 04/03/2016 07:55 PM »
I do not see here a better solution to remove small-size space junk.
Thank you Savuporo for sharing that info. OlegSerov, try not to be so dismissive, please.
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Offline OlegSerov

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Re: Orbital Debris Cleanup - how to?
« Reply #30 on: 04/04/2016 01:01 AM »
Well firstly, I'm curious what you think the "better" solutions are? I've not yet seen any I consider "good".

Always a good idea to look at what is actually being worked on, first.

http://www.esa.int/Our_Activities/Space_Engineering_Technology/Clean_Space/Technologies_for_space_debris_remediation


https://en.wikipedia.org/wiki/E.Deorbit

I do not see here a better solution to remove small-size space junk.

Because realistic solutions for tackling that problem are at very early technology development stage and not fully funded initiatives yet. Such as

http://www.spacesafetymagazine.com/space-debris/debris-removal/electrodynamic-debris-eliminator-receives-funding/

From the video:
Collect space debris weighting more than 2 kg in a net and then de-orbit them...

In my opinion it does not qualify as a "small space junk". Medium size - yes, but not small size.

Also: "ee of maneuverability across LEO and would be capable of collecting 136 sun-synchronous objects over a 3 year period." It will take forever to do it.

Offline savuporo

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Re: Orbital Debris Cleanup - how to?
« Reply #31 on: 04/04/2016 01:47 AM »
Also: "ee of maneuverability across LEO and would be capable of collecting 136 sun-synchronous objects over a 3 year period." It will take forever to do it.
Thats the reality of it, there are no quick and easy solutions.

Gas dispersion based systems have by the way also been proposed and studied, this was a serious NIAC study :

https://www.nasa.gov/pdf/716066main_Gregory_2011_PhI_SpaDE.pdf

http://www.spacesafetymagazine.com/space-debris/debris-removal/air-bursts-present-option-handle-space-debris/

In summary, energy requirements are unrealistic, and high altitutde airborne platforms for carrying such systems do not exist. Hence, TRL 2 and NIAC phase studies only.
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Offline gospacex

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Re: Orbital Debris Cleanup - how to?
« Reply #32 on: 04/04/2016 02:20 AM »
My pet idea for dealing with small (say, up to 30 cm) space junk is to build a spacecraft designed to survive multiple collisions with such junk, then launch it and, indeed, collide with debris, or "sweep up" debris until spacecraft is no longer redundant enough to be controllable after next expected collision or two. Then deorbit.

Offline Stan-1967

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Re: Orbital Debris Cleanup - how to?
« Reply #33 on: 04/04/2016 02:23 AM »
The net idea has good potential.   The problem according to ESA's roadmap is more in the guidance algorithms and sensors needed to capture the debris.   That is probably very challenging for smallsats, but in time, that would be ideal. 

I do wonder if a solid thin walled container would be better than a net.  I also think the intake capture mechanism should be something like a rear loading garbage truck, where there is a retainer plate to keep the already loaded garbage from falling out.   You basically have a "hopper" bin for capture, then push the debris back into the container.


I see a difficult trade for maximizing the mass and number of captured objects vs. the DV available for maneuvering and de-orbiting.

Offline savuporo

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Re: Orbital Debris Cleanup - how to?
« Reply #34 on: 04/04/2016 02:26 AM »
Here is a relatively recent summary talking about all currently proposed ADR ( active debris removal) methods, including dust, nets, ion, foam, airburst, lasers etc. and goes into pros and cons of each a little, too.

https://www.mcgill.ca/iasl/files/iasl/mlc-2014-burgess.pdf
http://www.rcaf-arc.forces.gc.ca/en/cf-aerospace-warfare-centre/elibrary/journal/2014-vol3-iss4-04-active-space-debris-removal-an-inevitability.page
http://www.rcaf-arc.forces.gc.ca/assets/AIRFORCE_Internet/docs/en/cf-aerospace-warfare-centre/elibrary/journal/2014-vol3-iss4-04-active-space-debris-removal-an-inevitability.pdf

They all have downsides, and statistically, the biggest threats are the large debris pieces. Thats why ESA is working on AR&D techniques and a demo for larger targets.
« Last Edit: 04/04/2016 02:27 AM by savuporo »
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Offline mikelepage

Re: Orbital Debris Cleanup - how to?
« Reply #35 on: 04/04/2016 05:57 AM »
Thanks for the links savuporo.  I hope everyone reads them.

Biggest take-home I gained from them is that if the objective is to at least maintain the status quo, that requires the removal of 5 or more large objects per year.  Large objects are chosen presumably because they are easier to target than the multitude of smaller objects which might collide into the large objects and create hundreds or thousands more small, hard-to-track objects.

Side note: I'm now avoiding use of the word "rendezvous" because it seems people often equivocate between two senses of it: 1) imply "match velocities with" or 2) "be in the same place at the same time".  Makes a big impact as far as space debris goes (rimshot).

For large objects above a certain size, it makes sense to have effector craft match velocities with the junk and deorbit/control it.

The much more prevalent small junk is going to remain an increasing problem however, and there are so many pieces in this category that it doesn't make sense to have an effector craft match velocities with them.

It seems to me the best solution is a two pronged approach with 1) matching velocities and netting large objects (which has a tech crossover with the asteroid redirect mission),  and 2) having a non-velocity-matching snowball cannon such as proposed above, or similarly using the Tungsten dust or air vortex methods mentioned in the links.

Offline savuporo

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Re: Orbital Debris Cleanup - how to?
« Reply #36 on: 04/04/2016 06:27 AM »
Large objects are chosen presumably because they are easier to target than the multitude of smaller objects which might collide into the large objects and create hundreds or thousands more small, hard-to-track objects.
Simply put, large objects represent a much bigger amount of stored kinetic energy ( E = 0.5 * m * v2 ) . On collision that energy will disperse and can have potentially catastrophic cascading effects.
Say a loose orbiting bolt slamming and puncturing ISS is not nearly as bad as two small LEO satellites in a head on collision.
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Offline savuporo

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Re: Orbital Debris Cleanup - how to?
« Reply #37 on: 10/29/2016 07:12 PM »
A new interesting paper to add
Ranking upper stages in low Earth orbit for active removal
Quote
5. Conclusions
The proposed ranking scheme was preliminarily applied to 529 rocket bodies in LEO, belonging to just 5 types, but accounting  for  more  than  64%  of  the  total  number  and  nearly  73%  of  the  total  mass  of  upper  stages  with  a  mean altitude below 2000 km. In terms of debris environment criticality, the sample analyzed was cumulatively equivalent to  1136  average  intact  objects  into  an  800  km  sun-synchronous  orbit,  with  a  mean  RN = 2.15 per  object.
  The environmental criticality was largely dominated by the 20 massive Zenit-2 second stages between 800 and 1000 km, followed by the Kosmos second stages, mainly between 750 and 1000 km,by the Tsiklon-3 third stages, around 950 km, by the Vostok second stages, between 800 and 900 km, and by the Delta 1 and 2 second stages, broadly scattered between 700 and 1800 km (Figures 6, 7 and 8 ). A further significant presence of Kosmos and Tsiklon-3 upper stages, even though quite lesser in terms of criticality ranking, was found between 1350 and 1600 km.


« Last Edit: 10/29/2016 07:15 PM by savuporo »
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Offline catdlr

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Re: Orbital Debris Cleanup - how to?
« Reply #38 on: 12/06/2016 11:23 PM »
Natalie Panek:"Let's clean up the space junk orbiting earth" - TED Talk

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Our lives depend on a world we can't see: the satellite infrastructure we use every day for information, entertainment, communication and so much more. But Earth orbit isn't a limitless resource, and the problem of space debris will get worse without a significant change to our behavior. Natalie Panek challenges us to consider the environmental impact of the satellites we rely on. Our orbital environment is breathtakingly beautiful and our gateway to exploration, she says. It's up to us to keep it that way.

http://www.ted.com/talks/natalie_panek_let_s_clean_up_the_space_junk_orbiting_earth?
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Offline ChrisWilson68

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Re: Orbital Debris Cleanup - how to?
« Reply #39 on: 12/12/2016 12:57 AM »
This thread was started to discuss one particular idea for removing space junk.

Some of the replies were about that specific idea.  But it has also become a magnet for any post at all about cleaning up space junk by any method.

Is there a generic thread for space junk removal in general?  If not, could we create one?  Then maybe we could get the mods to move the posts in this thread that aren't related to the original idea in this thread to that other thread and use that one going forward for the general topic of cleaning up space junk.

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