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The International Space Station   (Source: NASA)
Astronauts aboard the ISS were forced to sleep in Russian Soyuz escape pods due to a piece of flying debris

A small piece of space debris flew near the International Space Station (ISS) late last week, with ground control flight operators instructing ISS astronauts to hide in escape crafts.

The six-person crew aboard the ISS first learned of the debris early on Friday morning.  Since it proved so difficult to monitor it using satellite and ground-based technology, NASA said the piece of debris likely was extremely small.

Due to the space debris, the crew had to sleep in two Russian Soyuz craft designed to be escape pods -- the actual trajectory of the debris was unknown, causing even more alarm from mission operators.

It turned out, according to space officials, that the debris didn't come close to the ISS after all, but the decision to order the crew into the Soyuz escape craft was still a good idea.  

As the number of floating space junk increases, the possibility of impact with the ISS, satellites or manned missions has increased.  The ISS has been forced to undergo avoidance maneuvers in the past, but this may become an issue that is even more serious in the future.

The United States Air Force announced early last spring it would set aside $500 million in 2010 to help track space junk floating around Earth.  NASA officials also again said the threat of space junk would continue to increase unless space experts came up with methods to stop it.

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Relative velocities
By JediJeb on 11/10/2009 1:46:03 PM , Rating: 3
I know that objects in orbit are traveling at speeds of at least 17,000mph, but since velocity is related to orbital height, unless two object are on vastly different trajectories would they not have slow velocities relative to each other?

If you are traveling 60mph on the highway and another car at similar speeds hits you from behind very little damage occurs, yet a head on collision of two cars going 60mph would be horrific. Sure even a 30mph difference in speed could cause a lot of damage from a large piece of junk hitting the ISS, but I don't see things like screws and bolts ripping through it like bullets ( as they like to portray in the movies) unless it is moving in a retrograde orbit.




RE: Relative velocities
By nafhan on 11/10/2009 2:33:12 PM , Rating: 1
A piece of debris could be traveling at different inclination at the same height, or if it is not in a stable orbit, it could be going faster than orbital speed.


RE: Relative velocities
By Odysseus145 on 11/10/2009 2:37:41 PM , Rating: 3
Even if the difference in their trajectories is as low as half a degree, the debris will still impact at about 150mph. Which is more than enough.


RE: Relative velocities
By ThePooBurner on 11/10/2009 3:27:54 PM , Rating: 1
The Speed of a bullet is close to 700-800mph, and those can't always even pierce metal at point blank (being a sharp piece of metal vs just a bolt). 150mph shouldn't be a problem if they made the thing with any sort of thick walls for protection.


RE: Relative velocities
By BZDTemp on 11/10/2009 6:51:44 PM , Rating: 5
Nothing we put in space are any heavier than absolutely necessary!

Remember that bringing a payload into orbit is a big job and the actual payload weight vs. rocket/shuttle+rockets means each gram cost big bucks. Living in a space station is sort of living in a glass house - it is fine most of the time but when the kids next door play baseball it get's a little exciting :-)


RE: Relative velocities
By nuarbnellaffej on 11/10/2009 9:47:09 PM , Rating: 2
The walls of space stations are more like aluminum foil than armor plating.


RE: Relative velocities
By PrinceGaz on 11/10/2009 11:17:55 PM , Rating: 2
Exactly, or probably more like the strength of the side of a can of beer. A lot stronger than aluminium foil and not going to bent out of shape by mild impacts, but a solid projectile travelling at any speed will punch straight through.

In the orbit the ISS and other satellites there are in; other objects are travelling in all trajectories, meaning the average impact if it were to occur would come from a right-angle at a velocity of over 10,000mph. Some could be head-on at doiuble the velocity, whilst others might be very gentle contacts from an almost identical orbit.

A typical collision with the ISS if it was not moved out of the way would result in something like what happened to that Iridium satellite a few months ago which was hit by a Russian satellite (both in a fairly low orbit like the ISS is). Any sizeable object (basically more than a few millimeters in size) would almost certainly make the ISS module(s) it passed through unusable until the walls were repaired, or until emergency force-fields were erected in the effected areas (assuming such technology is available).

The US owes a lot to Russia for the ISS still being operational, it has to be asid, what with those docked Soyuz capsules being the crew's escape-pods, as well Russian launches during the Shuttle's past down-time allowing it to continue to be manned. Rather ironic that a failed Soviet state has been essential many times to the rest of the world's highest profile space programme continuing. Whilst I love progress, there's a lot to be said for tried and trusted technology (and yes, I am aware that Soviet launchers and capsules are progressing, but in a more progressive way rather than in big jumps).


RE: Relative velocities
By johnsonx on 11/10/2009 11:49:02 PM , Rating: 1
quote:
or until emergency force-fields were erected in the effected areas (assuming such technology is available).


Wow. If we didn't know before, we certainly know now to disregard anything you say. Go back to watching Star Trek.


RE: Relative velocities
By rykerabel on 11/10/2009 3:31:04 PM , Rating: 2
All low orbit trajectories vary by wide margins. Only high orbits like the Lagrange points and geostationary orbits don't have a wide range of trajectories. The ISS is in a low equatorial orbit along with old spy satelites that were in low polar orbits. Very very different trajectories with high angles of impact.


RE: Relative velocities
By JediJeb on 11/10/2009 5:00:29 PM , Rating: 2
I can see objects in polar orbits being the worse threat, 90degrees to the orbit of the ISS would probably give the greatest relative velocity difference. I can see angles of approach causing the largest variance in relative velocity since a higher total velocity would make for a higher orbit. ( centrifical force laws coming into play). I also didn't think about eccentricity of orbits either.


RE: Relative velocities
By zozzlhandler on 11/10/2009 5:55:47 PM , Rating: 3
What about 180 degrees? going the exact opposite direction would give an impact velocity of double the orbital velocity. I think that is the worst case scenario.


RE: Relative velocities
By Solandri on 11/11/2009 5:14:52 AM , Rating: 2
Pretty much all orbits (except polar) go in the same direction the earth is rotating. Launching in that direction (west to east) adds the earth's rotational velocity to achieve orbital velocity. Launching the other way (east to west), you would have to subtract the earth's rotational velocity, requiring even more energy than a polar orbit to achieve orbital velocity.


RE: Relative velocities
By JediJeb on 11/11/2009 5:04:08 PM , Rating: 2
Also retrograde orbits (reversed to the rotational direction of the planet) tend to slow an object down continually due to gravitational drag. Any object in a retrograde orbit would deorbit much sooner.


RE: Relative velocities
By kattanna on 11/10/2009 3:32:55 PM , Rating: 3
and its reasons like this, all the space junk that threatens even mobile space craft, that i am still laughing at the space elevator.

yes, lets stick a 22,000 mile long cable out into space. im sure it will be safe from all the debris.


RE: Relative velocities
By FaaR on 11/10/2009 7:33:09 PM , Rating: 2
It may be long, but it won't be very wide. Also, "all the debris" is a relative term; space - even the very insignificant bit in the immediate surrounding of planet Earth - is very big. So those fragments are extremely spread out; the risk of collision would be tiny to say the least.

Space elevators are probably impractical anyway, but for other reasons...


RE: Relative velocities
By Visual on 11/10/2009 7:53:29 PM , Rating: 2
Hurry up and stop laughing, you and everybody else... I want to see the elevator completed before the next 50 years ;)

If you think about it, the chances of a piece of space junk hitting a few centimeters wide ribbon are quite a lot smaller than it hitting a tens or hundreds of meters wide object like the ISS, no matter that the ribbon is stretching at all altitudes.

Plus, the base station will be mobile to allow position adjustments for the ribbons against the large debris that we can track, and there will be several parallel ribbons that should work as a decent backup if a small piece that we can not track happens to hit.

Lastly, a break in the ribbon would still not be anything catastrophic. The geostationary station and the counterweight will be safe even though they may enter a new orbit reaching a higher altitude. If we actually disconnect the counterweight then the station's orbit can remain completely unaffected as well.

There doesn't seem to be significant risk for human life at all, the destroyed ribbon and eventual cargo and climbers that were in transit at the moment will be the only loss. It's sure going to cost us some, but probably not as much as the savings we get from the elevator when it works properly.


RE: Relative velocities
By barjebus on 11/10/2009 3:49:49 PM , Rating: 2
I've always wondered this as well. Does space debris travel largely in one direction? If not, how much is traveling against the majority?


RE: Relative velocities
By Solandri on 11/11/2009 5:22:17 AM , Rating: 2
Except for equatorial orbits, all orbits are inclined. If you launch from Kennedy Space Center, it's at 28.6 degrees latitude. So the lowest energy orbit is inclined 28.6 degrees from the equator. That is, the ground track of the spacecraft will range from 28.6 degrees N of the equator, to 28.6 degrees S of the equator.

If you then launch another satellite from KSC at a later time, it will have the same orbital characteristics, but they two orbits will not be in sync. Worst case, when the first satellite is at 28.6 N, the other is at 28.6 S (remember, the orbit is fixed relative to a static reference frame, but the earth rotates underneath so a later launch will inject into a different orbit). When the two intersect at the equator, they will form a 57.2 degree angle, and thus have a rather considerable relative velocity.


RE: Relative velocities
By Smilin on 11/11/2009 8:49:14 AM , Rating: 2
They are almost certain to have "vastly different trajectories"

They would have slow velocities relative to each other for about 1 out of 360 degrees. The other 359 degrees are going to be lethal. That's also just thinking in two dimensions.

You are assuming that orbits are circular. Two objects at the same altitude are very unlikely to be in the same orbit and have the same velocity.

It should pretty much happen like you see in the movies.


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