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Satellite Debris Forces ISS Crew Into Rescue Craft
Muad'Dave writes "CNN is reporting that the crew of the International Space Station was forced to take refuge from a possible collision of the ISS with a piece of space debris Thursday. From the article: 'Floating debris from a satellite forced the crew of the international space station to retreat to a safety capsule Thursday, according to a NASA news release. .. The debris was too close for the space station to move out of the way, so the station's three crew members were temporarily evacuated to a the station's Soyuz TMA-13 capsule, NASA said.'" Update: 03/12 18:42 GMT by T : The original story incorrectly said the ISS had 18 crew members. Luckily for the three in the Soyuz, that was a mistake.
According to an article I just read*, that piece of junk was estimated to be about five inches in diameter and traveling at a relative velocity (to the ISS) of about 22,000 mph. That's almost ten kilometers a second**.
If that had hit the Soyuz, it would have went in one side and out the other likely without even slowing down much, vaporizing a significant chunk of the hull - think white-hot metal shrapnel and shredded astronauts.
Look at what happens to an armored tank when a depleted uranium shell hits it at a much slower velocity. At the velocities we're talking about here, even a pebble can cause a lot of destruction; a five inch piece of debris likely weighing at least a kg has an effect like a large artillery shell. Remember the flake of paint that put an inch diameter pit into the shuttle's windshield all those years ago?
The only effective armor against something like this is a meter or so of rock.
* http://www.usatoday.com/tech/science/space/2009-03-12-space-station_N.htm
**Google: 22000 mph in meters per second = 9834.88 meters per second.
SB
It's old. The more humans I meet, the more I like my cats. At least they are honest.
The chances of something from an entirely different orbit impacting a craft are still infinitesimal.
Much more likely than infinitesimal. As someone else commented, this has already happened. You must not have been watching the news lately.
The odds are either identically zero if the orbits do not intersect, or are small but significant if they do intersect. Orbits are not static and basically are never perfect closed ellipses, so there is a fair amount of fuzziness about whether two close orbits do or do not intersect. And, of course, every pair of orbits (about the same primary) cross twice on opposite sides of the planet - the two questions to ask are 1) whether they cross at the same altitude, and 2) whether the two objects are at the crossing at the same time.
Since an object in LEO completes about 15 orbits per day and each orbit crosses ALL others twice per orbit, there are many opportunities daily for collision. Most close passes are quite distant. Even if the two objects are near the particular crossing point the altitude may differ. Do the math, however, and you will find that there are several passages of two large objects within a few kilometers every single day. The odds of an actual collision then just scale as the volumes of the spacecraft divided by the volume of a unit cube. Wait long enough and they are guaranteed to collide.
All else being equal, the odds are about even that two large objects (spacecraft sized or so) will collide once per decade. There are hundreds of such orbiting objects, of course, so the odds for a specific satellite are something like once per a few millennia - for a collision with a similarly sized object. The odds are correspondingly larger for a collision between a spacecraft and the much more numerous pieces of small orbital debris.