Space debris

[vger]

The only way you'd want to use a railgun, is if the projectile was capable of somehow grabbing the entire chunk of debris, and dragging it out of orbit. All I see it doing is turning the object into smaller pieces, which would do nothing to reduce how dangerous they are.

[icemonkey]

The only way you'd want to use a railgun, is if the projectile was capable of somehow grabbing the entire chunk of debris, and dragging it out of orbit. All I see it doing is turning the object into smaller pieces, which would do nothing to reduce how dangerous they are.

Couldn't you just shoot it when it's coming towards you ie. hit it pointing retrograde, so it massively drops the velocity and it falls back to earth quicker?

[StuntMax]

There's an Anime called Planetes that covers this. I watched a few episodes, but didn't get too far.

The anime is basically crap, the manga is way better.

But it's really about loneliness of human beings and meaning of travelling without a place to return, the part concerning space junk is simply the setup. It's pretty good and kerbally enjoyable.

[StuntMax]

Didn't the USA shoot down a defective satellite with a missile launched from a boat?

USA used to develop this crap:

http://en.wikipedia.org/wiki/ASM-135_ASAT

Thanks god the USSR left the stage, if the cold war wasn't over we'd have a friggin' battlefield in the LEO... Kessler Syndrome Holiday Special Bonanza.

PS. is my grammar right? english is not my native language, i'm never confident on my grammar skills when I get into hypotetical sentences...

[peadar1987]

By and large, if you want to remove space junk, you have to go up there and get it (except in the extremely rare cases where it's small enough to be completely vapourised)

It's a common misconception that you can just blow something up in space, and that's problem solved. Not true. If you hit a spent final stage of a rocket, for example, with a railgun, you would smash the spent stage into pieces, each of those pieces having a different velocity. However, most of the pieces would still be going at roughly the same velocity they had before the impact (give or take a few tens or hundreds of metres per second). i.e. they would still have orbital velocity. You haven't solved the problem, because the debris is still in orbit.

What's more, because all of the parts of the smashed rocket are now moving at slightly different velocities, they will all be in slightly different orbits now. They will drift apart from each other slowly, and instead of one big chunk of debris a few metres across, you now have a cloud of debris several kilometres across, any one part of which can wreck a satellite or space station.

It is worth saying that while space junk is a problem, it's not as big as some people seem to think it is (yet). Space is absolutely huge, and the chances of encountering debris are very, very slim (in 60 years of space flight, we have had just eight collisions, in spite of the vast majority of what we have up there being pretty much uncontrolled most of the time)

My solution would be to enact a new and strict treaty against creating further space junk.

As for the stuff that's already there, I would put up a space station with a high-powered laser on board in any orbits thought to be at threat from debris. It watches retrograde for any debris. Small stuff, paint chips, etc, it can vapourise. Larger stuff, when hit by the laser, will be pushed backwards, speeding up the decay of their orbits.

[Seret]

Couldn't you just shoot it when it's coming towards you ie. hit it pointing retrograde, so it massively drops the velocity and it falls back to earth quicker?

That's about the only way it would work, but it would still be pretty risky and it'd involve positioning your gun at exactly the right point on the globe. Impacts are messy, getting the projectile to transfer all of it's energy directly along a retrograde axis would be pretty much impossible. Some of your debris would even have more energy after the impact than before.

Edited May 16, 2014 by Seret

[Idobox]

Laser broom: The idea is to shoot a high power laser in an area where there isn't anything valuable (ie working satellites), any debris present would be slightly ablated, which results in thrust and a change in orbit. For some of them, it means the periapsis will go down enough to decay rapidly, for the others, it will have to wait another sweep of the space broom.

It will work pretty well for LEO stuff (the square law means they'll get more energy, and they need less deltaV to decay), but it would destabilize the orbit of pretty much anything, and given enough time, will push everything either to decay or to reach escape velocity (that one would take very long though)

[xcorps]

That's about the only way it would work, but it would still be pretty risky and it'd involve positioning your gun at exactly the right point on the globe. Impacts are messy, getting the projectile to transfer all of it's energy directly along a retrograde axis would be pretty much impossible. Some of your debris would even have more energy after the impact than before.

You're saying that a 4 kg object travelling at 5500 m/s hitting at retrograde would make some of the debris travel at prograde faster?

Maybe you know enough about physics to provide some delicious sauce? (ie could you source that with something?)

[FenrirWolf]

The only way you'd want to use a railgun, is if the projectile was capable of somehow grabbing the entire chunk of debris, and dragging it out of orbit. All I see it doing is turning the object into smaller pieces, which would do nothing to reduce how dangerous they are.

I imagine the debris would be knocked into a more eccentric orbit. Maybe that alone would make them more prone to falling back to earth if they get a lower periapsis and more drag. Either that or the higher apoapsis means the debris spend less time in the more commonly occupied regions of LEO? I guess it depends on what angle and speed these railguns are supposed to be hitting the junk with.

[Idobox]

You're saying that a 4 kg object travelling at 5500 m/s hitting at retrograde would make some of the debris travel at prograde faster?

Maybe you know enough about physics to provide some delicious sauce? (ie could you source that with something?)

You would get debris flying in all directions, most of them out of the plan of the original orbit, and possibly, yes, some in the prograde direction. Look at pictures of crash tests, some debris flies backward, now imagine the wall is your original debris and the car is your slug.

[xcorps]

We aren't talking about cars and walls, we are talking about dead satellites in orbit getting hit by objects with enormous impulse.

If you could support your statement that'd be great.

(I don't mean to be contentious or disrespectful. I am not trying to be "I'm right you're wrong" here, actually looking for more info)

[Transits]

Deliver a Debris deorbiter using the Skylon SSTO (when it is created) to space, and send it around using ion engines to rendezvous with space debris. When it has collected enough, deorbit it and let it burn up in the atmosphere. This would not take too much money as one would only have to refuel Skylon and recreate the payload.

Also after that tell NASA and other space agencies such as the ESA to design rockets that leave minimal space debris, and maybe equip new sattelites with a new engine so that they can re-enter when they become redundant.

[sharpspoonful]

So you'll end up with more debris in a higher orbit? They would be smaller, and impossible to track.

There's an Anime called Planetes that covers this. I watched a few episodes, but didn't get too far.

I highly suggest watching the series. It delves into the problems associated with space travel, the threat space debris poses and the cost of cleanup, and the economic barriers that are indirectly imposed by the more developed nations. Also: moon city.

[Soda Popinski]

I highly suggest watching the series. It delves into the problems associated with space travel, the threat space debris poses and the cost of cleanup, and the economic barriers that are indirectly imposed by the more developed nations. Also: moon city.

Too many annoying stock anime characters.

As far as a rail-gun shot making something go faster than prograde, you could have a partially elastic collision. You could impart a lot of energy into a smaller mass, yielding a faster object. Either way, you'll have debris going in multiple unknown vectors. That seems worse to me than having a single known vector.

Also to the idea a naval rail-gun would be more accurate than a missile. I don't think that's necessarily true. Unlike a traditional ballistic arc, the missile was guided to the target, so any movement the ship imparts would be of minimal consequence. The missile launches relatively slowly, and gains speed over time. Any course adjustments made during the slow part of the ascent will have a correspondingly large change at point of impact. A rail-gun shot leaves the barrel at maximum speed, and only slows down. So any course corrections by the shot (assuming it's guided somehow) would need to be made rather quickly.

[peadar1987]

You're saying that a 4 kg object travelling at 5500 m/s hitting at retrograde would make some of the debris travel at prograde faster?

Maybe you know enough about physics to provide some delicious sauce? (ie could you source that with something?)

A 4kg retrograde projectile hitting at 5500m/s (so close to 13,000 m/s closing speed) will have an apparent kinetic energy to the target of about 338 MJ, or about the same as 100kg of TNT. This isn't going to be like a cannonball hitting a ship, or a bullet hitting a target, that much energy being released at once will blow up the target just as effectively as any live warhead. While conservation of momentum still applies, so the average orbit will indeed be lowered, the resulting explosion could quite well cause debris to be expelled in a prograde direction.

[xcorps]

could quite well cause debris to be expelled in a prograde direction.

In a NEW prograde direction...not the same prograde. There's no way that any particles wouldn't have increased velocity.

[YNM]

Bounce off radios on them and track them ? I mean, most (artificial) space debris is made of steel, and can reflect radio waves (on the correct wavelength). With a huge amount of transmitter on Earth, why nobody have thought of that ? I know, we don't get rid of them that way *cough what-if radar gun cough* but at least we can try learn how they behave, before actually sending anything to intercept them.

[peadar1987]

In a NEW prograde direction...not the same prograde. There's no way that any particles wouldn't have increased velocity.

Quite possibly the same prograde direction, or very close to it. The projectile is going to hit the target, and undergo a massive deceleration as it penetrates. The energy released in that deceleration will be released in all directions, including back in the direction the projectile came from.

[Kryten]

Bounce off radios on them and track them ? I mean, most (artificial) space debris is made of steel, and can reflect radio waves (on the correct wavelength). With a huge amount of transmitter on Earth, why nobody have thought of that ? I know, we don't get rid of them that way *cough what-if radar gun cough* but at least we can try learn how they behave, before actually sending anything to intercept them.

That's been being done for over fifty years.

[xcorps]

Quite possibly the same prograde direction, or very close to it. The projectile is going to hit the target, and undergo a massive deceleration as it penetrates. The energy released in that deceleration will be released in all directions, including back in the direction the projectile came from.

Yes, but the debris will have increased velocity, therefore a different orbit. Therefore a different prograde. How much velocity is the question. I searched around for a while trying to get some idea of how fast the particles would be moving, and I'm getting the impression it would be PDF. (pretty damn fast) No more circular orbit, surely, therefore no problem. But like I said, I'm not trying to be contrarian. If someone demonstrates to me that the new debris field from say a destroyed booster that was in LEO would STAY in LEO, I'll concede that a couple of rail guns firing in tandem with small projectiles is a bad idea.

OH wait, I got it. I GOT IT....

A VACUUM CLEANER!

Edited May 17, 2014 by xcorps

[Kryten]

That debris from destroyed objects in LEO will stay in LEO is easily demonstrated by looking up anything about the 2007 Chinese ASAT test and the 2008 US test that most certainly wasn't a response to it. Both cases involved sats being hit by missiles with very low orbital velocities, and both created debris with significantly higher orbital velocity than the initial sats.

[xcorps]

That debris from destroyed objects in LEO will stay in LEO is easily demonstrated by looking up anything about the 2007 Chinese ASAT test and the 2008 US test that most certainly wasn't a response to it. Both cases involved sats being hit by missiles with very low orbital velocities, and both created debris with significantly higher orbital velocity than the initial sats.

The debris field from an ASM135 kill against a Solwind P78-1 satellite in 1985 deorbited in the late 90's.

the 2008 US test

I think you are referring to USA-193?

Edited May 17, 2014 by xcorps

[Kryten]

I think you are referring to USA-193?

Yes, a number of tracked pieces of debris ended up with higher apogees than they started with, and lasted a lot longer then they were supposed to. 'A lot longer' in this case is a year rather than a few months due to the very low orbit involved, but it still demonstrate the point.

[xcorps]

That satellite was destroyed with a SM3 AAM. It delivered 130mj. The rail guns being developed that I was using as example figures generate 360ish...

And all the debris DID deorbit.

[YNM]

Bounce off radios on them and track them ? I mean, most (artificial) space debris is made of steel, and can reflect radio waves (on the correct wavelength).

That's been being done for over fifty years.

But a bad news because it said that it's halted since 2013...

A stupid idea (that works) : deorbit all active satellites, move off ALL people from space, and initiate the sun to cough us an X-class flare. No debris, no electricity too through.