Guess what ESA is planning to do with space junk.

[YNM]

The true tried-and-tested method is :

Atmospheric braking.

It has gunned down good number of space stations, even !

[PB666]

Quote

Or medium things (mass of a ton) like Dawn or New Horizons over a loooong time. Anything that is based on reaction, like harpoon, tether, etc. needs some mass. Imagine ESA shoots the harpoon, the harpoon stays where it is and the empty tube flies in the other direction. Kerbal style :-) Ion drives of the day don't have enough oomph to adjust orbit of a deorbit satellite in LEO. In less than months or even years of time, and then the problem might be gone anyway, or has changed orbit due to interaction, or just because ...

It takes very little dV for most satellites to clear them from LEO, since a good segment are between 250 and 500 km.

Let do the math for 500 km

r_pe = 6371000 + 120000 = 6491000. r_apo = 6371000 + 500000 = 6871000 a = 6681000 (Note to YNM this is atmospheric breaking)

since the craft will be deorbited at r_apo to intersect r_pe we want to know the starting and final velocities at apo. Assuming a circular orbit.   V_{6871000, cricular} = 7616.6 V_{6871000, a} = SQRT(µ (2/r - 1/a) = 7507.47
dV = 7616.6 - 7507.5 = 109.1 m/s.

Lets say you have a six ton satellite that can only thrust 1/3 rd of the time. The disposal vessel weight say 1000 kg with 4 Bit7 thrusters (44 mN) . So the total mass is 7000 kg. and the time required

3 * 109.1 m/s * 7000 kg / (86400 * 0.044 N)  =  603 days. This requires a power supply of 1800 watts (the weight of the thrusters is trivial). If you add more thrusters of course you need more power. Note the number of thrusters is really dependent on the amount of power available. But with four RTGs the tug, somewhat less efficiently, retrograde over 270' instead of 120 degress and markedly speed up its operation. 

dv = 109.1 = 3300 * 9.8 * ln (M_i/M_f) = 0.0033 * 7000 = 23.65 kg of fuel, with about 1/7th of this it can return to orbit. So that the total cost is 30 kg of fuel. Lets say the satellite cost 2 million dollars and it has on board 300 kg of fuel. Then it is possible for it deorbit satellites at the cost of 200,000$ each plus the cost of launch, since its weight is around 1 ton, y could be launched on a single SpaceX for about a third the cost of an ESA launch. In addition the satellites, being self propelled could return to an argon tank (8000 kg) in LEO and refuel, then go about deorbiting many other satellites.

So basically 8 satellites could be deorbited over the period of 2 years or 4 per year, over the course of say 40 years this could be done 20 times per satellite or 80 satellites deorbited. That all cost of 2 space X rocket launches, so how much is ESA planning to spend each launch.

Of course for satellites in much further orbits this is more difficult and may require more thrusters.

 

Edited March 15, 2018 by PB666

[Starman4308]

7 hours ago, p1t1o said:

Lets be honest. None of these things are going to work because there are too many objects, and thats not even counting things like debris or shrapnel.

The only way to solve it properly is if we all agree to not use space at all for a few years, then we nuke the feaces out of the whole zone. Just literally go to town. Keep going until the statistical probability that there is anything significant left in orbit asymptotes to zero.

Then we can go back to space....but carefully this time.

Nukes in space don't work that way. Even if they did work the same as in atmosphere, there's simply too much of space to feasibly nuke it.

Anyways, the harpoon thingy seems like a decent proposal to deorbit some of the larger defunct satellites in LEO/MEO (I'm a bit fuzzy on where the boundary between low and middle Earth orbit is). There's some stuff that would otherwise stay up there for centuries to millenia, but which need only a touch of delta-V to put into a swiftly-decaying orbit.

The smaller stuff hopefully just decays on its own, or is in a high enough orbit that it's unlikely to pose a navigation hazard.

[DerekL1963]

21 minutes ago, PB666 said:

Lets say the satellite cost 2 million dollars and it has on board 300 kg of fuel.

Assuming you pay slave wages to the magic pixies doing the assembly work and steal your material at gunpoint (without getting caught)...  you might get prices down that low.

Otherwise, no.

 

26 minutes ago, PB666 said:

It takes very little dV for most satellites to clear them from LEO, since a good segment are between 250 and 500 km.

0.o  Nobody worries too much about dead birds in that range.  That range (especially the lower end) is rapidly swept clear by atmospheric drag.  I mean c'mon - ISS is only 400km up and it requires regular reboost.  Sputnik I was at 577km and it's long gone.  The worry in that range is heavy small debris - stuff with a high ballistic coefficient that isn't effected as much by drag.

Take a gander at this graphic showing all birds in orbit as of 2015 - there's a reason why the population suddenly explodes at around 400km.

https://qz.com/296941/interactive-graphic-every-active-satellite-orbiting-earth/

[PB666]

37 minutes ago, DerekL1963 said:

https://qz.com/296941/interactive-graphic-every-active-satellite-orbiting-earth/

This is the one from NASA, most of the satellites are very close to what I said. The earth is 6,371 km, 500 km is one twelfth, the desities start around 1/15th of the radius or 450 km,  targets at 500 km are choice because these will soon cross the path of the ISS. as these are depleted they could progressively go after more distant satellites. But examining the density of craft at the poles. Again one does not have to drop the satellites, the tugs could thus take them to stations where they are combined and sent into a burn-up orbit by occasionally launched spacecraft like F9. The point is that its not hard to remove most and the most dangerous junk (that which is in highest density).

Edited March 16, 2018 by PB666

[KG3]

Crackers!  Whose gunna pay for all this!!!

It sounds like whatever the method(s) used it's going to be nearly as expensive to take something out of orbit as it is to put it up there in the first place.  Is there some way to factor in the cost of cleaning up debris to the cost of new missions?  Are businesses who build and maintain satellites getting better at planning to deorbit their stuff when they are done with it?

[T-10a]

30 minutes ago, KG3 said:

Crackers!  Whose gunna pay for all this!!!

It sounds like whatever the method(s) used it's going to be nearly as expensive to take something out of orbit as it is to put it up there in the first place.  Is there some way to factor in the cost of cleaning up debris to the cost of new missions?  Are businesses who build and maintain satellites getting better at planning to deorbit their stuff when they are done with it?

AFAIK, most modern sat providers are required to put their satellites in graveyard orbits at the end of operational lifetime, so their debris and junk will not destroy major geosynchronous satellites. For LEO sats, I do not know of any regulations (I'm happy to be shown any, the more we can be aware of solutions to Kessler Syndrome, the better!)

[Starman4308]

2 hours ago, KG3 said:

Crackers!  Whose gunna pay for all this!!!

It sounds like whatever the method(s) used it's going to be nearly as expensive to take something out of orbit as it is to put it up there in the first place.  Is there some way to factor in the cost of cleaning up debris to the cost of new missions?  Are businesses who build and maintain satellites getting better at planning to deorbit their stuff when they are done with it?

Depends, I think. For certain very common orbits, it may be possible to sweep out several satellites without much delta-V. For sun-synchronous, for example, one might be able to clear out a few, deliberately break into a precessing orbit, sweep some more, etc. While final rendezvous would probably be done on chemical engines, I suspect some high delta-V maneuvers could be done on ions, such as the plane changes/precession maneuvers necessary to hit multiple sun-synchronous orbit planes.

[DerekL1963]

On 3/15/2018 at 6:03 PM, PB666 said:

This is the one from NASA, most of the satellites are very close to what I said. The earth is 6,371 km, 500 km is one twelfth, the desities start around 1/15th of the radius or 450 km

0.o  Your defined range was 250-500km.  If the density starts at 450km (I said 400, but no biggie) - then (as I pointed out) the bulk of your defined range is empty [snip]
 

On 3/15/2018 at 7:20 PM, T-10a said:

AFAIK, most modern sat providers are required to put their satellites in graveyard orbits at the end of operational lifetime, so their debris and junk will not destroy major geosynchronous satellites. For LEO sats, I do not know of any regulations (I'm happy to be shown any, the more we can be aware of solutions to Kessler Syndrome, the better!)

AIUI That's one of the big concerns about the proposed internet provider constellations - they're huge, in the way of access to geosync, the various constellations overlap each other...  And there's no clear regulation or agreement about graveyard orbits or deorbit capability.

Edited March 17, 2018 by Vanamonde

[Green Baron]

6 hours ago, KG3 said:

Crackers!  Whose gunna pay for all this!!!

It sounds like whatever the method(s) used it's going to be nearly as expensive to take something out of orbit as it is to put it up there in the first place. 

Yes. So it seems.

[p1t1o]

9 hours ago, Starman4308 said:

Nukes in space don't work that way.

Sure they do. One nuke per debris object. Everything is vapour. Problem solved.

This may be tongue in cheek.

 

[KG3]

8 hours ago, T-10a said:

AFAIK, most modern sat providers are required to put their satellites in graveyard orbits at the end of operational lifetime, so their debris and junk will not destroy major geosynchronous satellites. For LEO sats, I do not know of any regulations (I'm happy to be shown any, the more we can be aware of solutions to Kessler Syndrome, the better!)

Are there actually regulations for satellites?  How does building the capability to deorbit into the satellite in the first place effect the cost?  How often do controllers loose contact with satellites before they get the chance to deorbit or put them into a parking orbit?

[James Kerman]

Quote

Designers of a new vehicle or satellite are frequently required to demonstrate that it can be safely disposed of at the end of its life, for example by use of a controlled atmospheric reentry system or a boost into a graveyard orbit.[8] In order to obtain a license to provide telecommunications services in the United States, the Federal Communications Commission (FCC) requires all geostationary satellites launched after March 18, 2002, to commit to moving to a graveyard orbit at the end of their operational life.[9] U.S. government regulations require a boost, Δ H {\displaystyle \Delta {H}} , of ≈300 km.[10]

https://en.wikipedia.org/wiki/Kessler_syndrome

I do remember reading a proposal or maybe an article where satellite operators could be required to comply with "One up, one down rules".

Edited March 16, 2018 by James Kerman
Spelling

[PB666]

8 hours ago, DerekL1963 said:

0.o  Your defined range was 250-500km.  If the density starts at 450km (I said 400, but no biggie) - then (as I pointed out) the bulk of your defined range is empty not "close to what you said".  Don't try and rephrase what you said to make it look like you're correcting a misstatement on my part.

Of course you are going to start close to the low end of the range and clean upwards, make sense because your ellipse is in the 120 to 500 range so clean that area up first before moving upward, plus that currently is the range of manned space flight, so yeah 250-500 for starts. But a 250 km orbit is a trivial clear since apogee is low you need only to remove 25 m/s and release, the higher the object is the lower the perigee needs to be to bring its apogee down. Plus, as I said, you want to test flight systems. you don't want to be harpooning satellites in ISS orbit in your trial phase, that would be dumb.

I said in the beginning, during the training period you needed to practice on objects that would clear anyway. As I demonstrated numerically it takes 109 m/s to cross the range, so you want to first work on things that anything you do will be less than 25 m/s as not to throw them back into the range that might collide with important stuff.

This brings up another problem as you mention the why. The why and the how are connected, not only do sats need to be brought down, they also have be brought down in one piece, but also from orbits where they may not be interfering with other craft, crossing orbits that may interfer with other craft. For example a sun synchronous orbit has may craft in it, if you slow it down a bit other craft may start passing the craft, so the best way to handle that is to burn retrograde at perigee and then burn at apogee just to get it out of the path of other similar orbits, then deorbit by burning from apogee.

Edited March 16, 2018 by PB666

[PB666]

8 hours ago, DerekL1963 said:

AIUI That's one of the big concerns about the proposed internet provider constellations - they're huge, in the way of access to geosync, the various constellations overlap each other...  And there's no clear regulation or agreement about graveyard orbits or deorbit capability.

Are you saying this is the reason the FCC refused the license, as far as I know the reason was not given.

[MaxwellsDemon]

Whenever I see a discussion about dealing with space junk, I'm inevitably reminded of the old Andy Griffith show, Salvage-1.   (Forgettable show, but a neat-looking spacecraft...)

Edited March 16, 2018 by MaxwellsDemon
spelling correction

[kerbiloid]

BF(R/S) can fly and catch them with jaws. Then return.

 

Edited March 16, 2018 by kerbiloid

[wumpus]

23 hours ago, DerekL1963 said:

Setting aside the fact that the harpoon is simpler than the non-existent space bots, such bots don't exist.  The harpoon is also at least a couple of decimal places cheaper than the complex and non existent bots.  (Yes, complex - maneuvering in 3d remotely, dragging a rope around, etc... etc... not gonna be cheap or simple.  Don't even try to claim otherwise.)

What is firing the harpoon?   It is in a polar orbit so firing from the ISS is out of the question.  Are you suggesting mounting it to a Soyuz [Dragon, or similar]?  Some non-existent space robot will be needed to fire the harpoon.

The harpoon is also listed as extremely specific to hitting Envisat, with subsequent harpoons designed for each individual bit of space junk.  I also have to ask what is on the other side?  A parachute?  A giant umbrella (because the air won't open the chute)?  I'd guess it simply adds the ~100m/s via solid rocket to deorbit the thing.  I'd recommend your space robot using ions to change orbits and attaching solid boosters (to dribble out 100m/s over 10 minutes) for deorbiting (you don't want your ion craft in the atmosphere, although if the bird is too high, you might lower the Pe via ions and do the last bit with SRBs).

I can see that large (relatively dense) objects in LEO might take some time to come down (Skylab took what, 10 years?).  Objects in polar orbits (like Envisat) are a huge danger thanks to relative velocities at orbital speeds (although I'd hate to think what relative speeds two objects in Baikonur inclination can hit).

Finally, how much delta-v do you need?  LEO-Earth (in one orbit) looks like ~100m/s.  GSO-Graveyard is said to take 10m/s (according to the infallible wiki), but I really don't expect two GSO satellites to ever hit.  Elliptical orbits should get fun, although presumably dropping the Pe into the atmosphere should be less expensive than dropping from circular into the atmosphere, and if it is high enough it shouldn't matter).  Getting your space robot to intercept such a beast might be more fun.

[DerekL1963]

12 hours ago, wumpus said:

What is firing the harpoon?   It is in a polar orbit so firing from the ISS is out of the question.  Are you suggesting mounting it to a Soyuz [Dragon, or similar]?  Some non-existent space robot will be needed to fire the harpoon.

1) ask the ESA, it's their plan.
2) Who proposed firing it from ISS?
3) I made no suggestions, see #1.
4) Is completely irrelevant, I was discussing the complex autonomous rope wrangling 'bots in PB 666's scheme.  Since we know nothing about the ESA's plan, there's nothing to criticize.
 

14 hours ago, PB666 said:

Of course you are going to start close to the low end of the range and clean upwards

Once again,  you said nothing about starting at the low end of the range.  You said nothing about testing and practicing first.  You said "It takes very little dV for most satellites to clear them from LEO, since a good segment are between 250 and 500 km", which I showed to be incorrect.  [snip]
 

14 hours ago, PB666 said:

Are you saying this is the reason the FCC refused the license, as far as I know the reason was not given.

The only people I know of offhand who have been denied a license by the FCC were denied (IIRC) because of issues with tracking them, not with disposal.  Is that who you're thinking of?

Edited March 17, 2018 by Vanamonde

[PB666]

7 hours ago, DerekL1963 said:

Once again,  you said nothing about starting at the low end of the range.  You said nothing about testing and practicing first.  You said "It takes very little dV for most satellites to clear them from LEO, since a good segment are between 250 and 500 km", which I showed to be incorrect.  
 

 

Edited March 17, 2018 by Vanamonde

[Green Baron]

17 hours ago, James Kerman said:

I do remember reading a proposal or maybe an article where satellite operators could be required to comply with "One up, one down rules".

There are several proposals to deal with the problem. De-orbit after a satellite's lifetime, raise the orbit to a "graveyard orbit" where it is out of the way, etc. Afaik nothing is mandatory until now, the interest of the biggest space nations to do something against the problem seems to be low ...

[snip]

Edited March 17, 2018 by Vanamonde

[Vanamonde]

Some personal remarks have been removed from this discussion. 

[StrandedonEarth]

On 3/16/2018 at 7:09 AM, kerbiloid said:

BF(R/S) can fly and catch them with jaws. Then return.

 

As long as they don't pick the wrong target....