Japan launched a cargo ship which will use a half mile tether to remove debris from Earth's orbit.

originally posted by: Bedlam

originally posted by: TheAlleghenyGentleman
a reply to: Bedlam

Well, possibly right?

But.....

I can't imagine it would all incinerate though.

Unless it's really tough, yeah, it'll burn up.

There's images all over the net of weird, strange looking space debris that at first was thought to be possibly debris from UFO's (yeah..i know) but later identified as oxygen tanks, fuel tanks or other components from space vehicles falling back through the atmosphere to Earth...the point being, many pieces of this debris do not burn up but remain largely intact and crash into the ground.

Imagine a two to three foot diameter titanium oxygen sphere crashing into your head from space...it'll take more than a painkiller for that kind of headache mate.

a reply to: MysterX

Presume the net will be moving at 1700MPH then slow slowly until re entry and burn ?

a reply to: skywatcher44

That would assume that all the debris is travelling along the same vector...is it do you know?

originally posted by: skywatcher44
a reply to: MysterX

Presume the net will be moving at 1700MPH then slow slowly until re entry and burn ?

What would the weight of that haul be? Can we really trust that it will all burn? What would the results of even a guided impact be if the pieces or the mass was not completely burned?

Cool beans.

Glad to see someone is trying to do something about all the junk up there.



Maybe one day we can invent a funky laser weapon to zap all the junk into space dust.

How fun would that be ??

Pew pew... pew pew pew !

a reply to: Joneselius

The point is that most of the junk is small, it will be things like, nuts and bolts or components from explosive separation, dead satellites that are still up there but otherwise tracked only by ground optics. Truth is that it is everywhere, but what we have on our side is statistics. Ever dropped a small screw on the floor and spent 20 minutes looking for it? its like that... except rather than dropping it on the floor, you are dropping it in a lake.

Do this thought experiment. Lets say you had 1 million people and you distributed them evenly across the Earth. Would anyone be able to see anyone else? No likely not since each person will roughly have 500 square km to look over.

So if you extend that surface into a 3d skin, you have a volume problem rather than a simple surface problem. Debris occupies a vast volume around the Earth, and much of it orbits very similarly to other satellites or objects (like the ISS) so the chances of just randomly flying by something and seeing it is very very slim.

If you have ever seen Mission to Mars... with the Satellite jump... or Gravity with the HST to ISS to (other) Space station jump.... you should realize that performing those jumps is basically impossible. Chances of you randomly entering Mars orbit near to a satellite as shown is just ridiculously slim. The jumping down orbit as shown in Gravity... is just impossible, you'd not be able to even see the objects you are trying to jump to.

As has already been put, there are a lot of objects up there floating about that are looking down here. Will it differentiate and miss those. Especially when the people who put those objects up there did not and will not tell anybody where and what they are.

Some day maybe we'll learn not to poop in our bathwater. I think the people who designed all this crap should be shot into orbit with a trash bag and pointy stick to clean up their mess.

a reply to: Bedlam

I am asking about how they deal with the consequences of Newton's Third Law. Every time this thing displaces a piece of junk it must lose momentum.

There is no net, only an electric tether. How does this satellite stay in orbit long enough to do a meaningful job?

originally posted by: Astyanax
a reply to: Bedlam

I am asking about how they deal with the consequences of Newton's Third Law. Every time this thing displaces a piece of junk it must lose momentum.

There is no net, only an electric tether. How does this satellite stay in orbit long enough to do a meaningful job?

The 'net' is utilizing the Earth's magnetic field.

When an conductor (the net in this case) moves through a magnetic field it will generate a current (think of the glowing tether from NASA experiments). These currents will then generate a magnetic field (quite a large one given the magnitude of electric field the Earth generates).

Magnetic fields can only change the direction of other moving particles and so you do not have a general momentum problem. The mass of the 'net' is large enough that the forces acting on it will be negligible. The 'net' wont come in physical contact with most of the debris, it will only experience a force in the form of magnetic or electric forces generated by the debris (only conductive debris like metals).

Fm = IL x B (I = current, L= Magnitude of length and directional vector , x = cross product and B = magnitude of magnetic field and directional vector).

Fe (electric force is likely negligible due to orientation of 'net').

The debris on the other hand (due to the orientation of the magnetic field) will force a "large" swathe of the debris into unstable orbits causing them to enter the Earth's atmosphere thus clearing the skies.


Fun fact: There is a Japanese anime about cleaning up space debris called Planetes. I must say though that the current approach is much more practical than that of the show (I *loved* this show back in high school)



-FBB

originally posted by: Joneselius
What I don't understand is where the space junk is?

The picture makes it seem like it's all over the place and would be easily visible if you were above the Earth.
The ISS live feed that was shown, which had it's camera pointing directly at Earth, showed no such problem, you couldn't see any space junk at all, none.

Is it black? Dark? Is it hard to see?

It IS all over the place. The debris is traveling incredibly fast and occasionally collides with other objects which results more, smaller pieces of debris, and so on. The energy involved is incredible, kinetic energy (like car crashes) are modeled with (1/2)x(mass)x(velocity x velocity) so the speed is much more important than the size of the debris.

for example :
space debris


The debris is measured with radio waves to an incredible accuracy from both the Earth's surface and satellites.

The space the debris can occupy is so vast that seeing it visually is not reliable so radio waves are used.

-FBB

a reply to: FriedBabelBroccoli

Even so, it is the satellite's (or rather the tether's) own kinetic energy that is being converted to electricity. So how does it stay up? Or does it, too, come crashing down to Earth?

originally posted by: Astyanax
a reply to: FriedBabelBroccoli

Even so, it is the satellite's (or rather the tether's) own kinetic energy that is being converted to electricity. So how does it stay up? Or does it, too, come crashing down to Earth?

Yes. That's the point. It's sort of like flypaper that grabs some amount of crap and then de-orbits using a passive tether.

originally posted by: Astyanax
a reply to: FriedBabelBroccoli

Even so, it is the satellite's (or rather the tether's) own kinetic energy that is being converted to electricity. So how does it stay up? Or does it, too, come crashing down to Earth?

Not quite.

The electric field generated by the Earth is what is generating a current in 'net. The current in the 'net' is then producing a magnetic field/' The kinetic energy is not related to the magnetic field being generated aside from sharing a velocity.

Further the force of the debris in the magnetic field (remember the current in the net generates a magnetic field) is negligible. The force is negligible because of the difference between the two masses (Space Station vs a screw). The momentum between the debris and space station occurs, but the ISS is equipped with equipment to adjust for that (bursts of air or from other chemical reactions).

The Earth is constantly accelerating the ISS so it will quickly return to the proper stable orbit if the cumulative effects of moving debris manages to change the ISS's orbit.

The ISS is essentially in continuous free fall.


-FBB

a reply to: ErosA433

Okay I understand that, thanks for the great explanation too.

How come the ISS isn't shredded to pieces or any satallites though? Surely they would have been hit by now.

I think cleaning the debris out there is a fantastic idea. But I am concerned about a potential downside to this effort. Right now we pretty much know where the debris is. What happens when this device only changes the trajectory of some debris rather than gather it up and pull it out of orbit? What would normally pass by the ISS may be on a collision course after this device passes by.

originally posted by: Joneselius
a reply to: ErosA433

Okay I understand that, thanks for the great explanation too.

How come the ISS isn't shredded to pieces or any satallites though? Surely they would have been hit by now.

There are many different orbits which a satellite can occupy and the Earth is massive. Some orbits are generally more safe than others due to elevation and orbit path.

The ISS does take hits though:
Space debris hitting ISS window creates 7mm chip

To keep ISS, and any other space vessel and satellite out of the danger zone, NASA and the Department of Defense have a system in place for tracking any potential threat. The Space Surveillance System is able to identify and keep tabs on debris as small as 5cm in low Earth orbit – that’s where the station resides.

The government agency has a three tiered system to classify the urgency of the threat. In the case of the ISS, if Moscow or Houston space centers are able to identify the threat in advance, they can re-position the station to avoid being struck. There is quite a wide breadth of area that objects are considered dangerous to pass through, or close enough, to the space station. The “pizza box” zone is roughly 1 mile deep, and 30 x 30km with the ISS in the center. Anything that enters this area will alert ground control and the crew and they will determine the best course of action.

Here is a picture from the impact:
Boom

Space is not for the faint of heart if dust can wipe out an entire vessel. lol

-FBB

originally posted by: cprnicus
Some day maybe we'll learn not to poop in our bathwater. I think the people who designed all this crap should be shot into orbit with a trash bag and pointy stick to clean up their mess.

you didn't design it so I broke this whole universe in half and it showed up. I told it that it was your fault but still not enough people sitting on their hands to justify that one. We were able to get a killing machine in charge of creating though. Baby steps.

a reply to: Bedlam

So it only grabs a bit (or two)?

Unimpressive.