What can be done about space junk

[WhoWee]

The collision of satellites in space this week reminds us all about orbiting space debris. What CAN be done about the problem? Is anyone working on a long term clean-up strategy?

This isn't my idea of entertainment.
http://news.yahoo.com/s/ap/20090216/ap_on_sc/falling_debris

 

[D H]

There is nothing that can be done about the existing space debris other than to let atmospheric drag slowly solve the problem for us. That debris is spread out amongst a wide variety of orbits. Collecting it somehow is an insurmountable problem. The long-term solution is to not let it accumulate in the first place. Vehicles must safe themselves at the end of their life by performing one last set of burns that either place them on a safe reentry trajectory or move them well out of harm's way. The Space Treaty suggests, but does not require, this treatment. Even then, some vehicles will (and do) fail. There will still be some accumulation of space debris.

 

[redargon]

sharks, with frikkin' lasers on their heads, muwhaahahahaha.

how about we just classify it with all the other garbage that we can't get rid of (nuclear waste, PET, etc etc) and hope the next generation will take care of it. It will definitely leave us more time to enjoy the global warming.

 

[redargon]

sorry, feeling particularly cynical today...

 

[mgb_phys]

Can't we just build a rocket from stuff in the junk yard and go and collect the scrap?
http://en.wikipedia.org/wiki/Salvage_1 - for those of us who watched too much TV in the 70s

 

[BobG]

There is no good strategy for removing debris already in orbit. Like DH said, the only feasible methods are to reduce the rate that debris increases: http://orbitaldebris.jsc.nasa.gov/library/2007_STSC_SD_Mitigation_Guidelines.pdf . And that's reduce the rate that debris accumulates. At this point, space debris will become a bigger and bigger problem no matter what since the satellite business has become more and more profitable in an information age.

The fireball over Texas was not related to satellite debris, though. It was a natural meteorite, most likely much larger than normal since fireballs during the day are extremely rare. This is a blog instead of a news source, but it does a better job of gathering tidbits of information than the FAA has given to the news media (natural since the FAA has nothing to do with monitoring satellites in orbit - the news media should have been asking NORAD): Texas fireball.

There really does need to be a central organization that coordinates satellite traffic, much like international air traffic control. One problem is that space programs have dominated by military progams and most nations aren't eager to give any information on their satellite operations.

In fact, the US military's satellite surveillance system has made a limited amount of information available to the public in order to push any outside providers out of the picture (a little similar to their strategy on making GPS data available to the public). In return to providing more accurate data on most satellites, they prevent the distribution of information on military satellites.

Given the amount of free data available, the Iridium-Cosmos collision could have been avoided if any civilian company actually took that info and analyzed it for possible collisions (the US military already does that for their own satellites, but doing it for everyone's satellites would probably be beyond the capability of their system).

 

[mgb_phys]

Presumably this is only a problem in LEO where you have lots of satellites in different inclination orbits? Where atmospheric drag is going to bring debris down fairly quickly.

At Geostationary, everything is going to be going in the same direction and there is a lot more space at 36,000km than 500km - so is junk not a problem if a large telecoms satellite blows up?

 

[BobG]

Presumably this is only a problem in LEO where you have lots of satellites in different inclination orbits? Where atmospheric drag is going to bring debris down fairly quickly.

At Geostationary, everything is going to be going in the same direction and there is a lot more space at 36,000km than 500km - so is junk not a problem if a large telecoms satellite blows up?

You won't get the incredibly high velocity impacts at geo that you get in low Earth collisions near the poles, but there can still be some pretty high speed collisions between satellites (around 500 m/s closing speed, or about a 1000 mph). Because the Earth isn't a perfect sphere and because the Sun/Moon affect satellite orbits, you get perturbations in the orbits. If a satellite dies unexpectedly in the geosynchronous belt, it's longitude drifts back and forth across the geo belt. It's inclination also changes (eventually, all satellites would wind up in the ecliptic plane after enough millenia). That means some dead geo satellites pass right through the live geo belt at an angle two times a day.

Around the equator, you could generally say you have a "gravity valley" at about 105 degrees West longitude and at about 75 degrees East longitude. A satellite that dies in the geo belt will oscillate between those two longitudes for centuries, at least. The inclination increases to around 15 degrees, then goes back to zero over about a 30 year period, then increases, etc. You get the cyclic action because the right ascension of ascending node is changing because of the Sun/Moon as well.

Over time, the Moon has been pulled into an inclination that's within 5 degrees of the ecliptic plane (the plane of the Earth's orbit around the Sun, which is inclined 23.4 degrees with respect to the equator). Having less mass, it shouldn't take near as long to pull satellites into the ecliptic plane, but certainly a long time relative to the average human's life span and a long time relative to the current age of the space age.