March 14, 2009

Collisions of an unusual nature have been in the news lately. First, we had the story about the satellites, one Russian and one American, colliding in space and then only days later, two heavily armed and highly dangerous nuclear submarines belonging to Britain and France collided in the vast empty spaces beneath the Atlantic Ocean. Two one-in-a-million collisions, it would seem.

Space objects have collided accidentally in orbit before, but these were considered minor incidents and involved either leftover portions of used rockets or small satellites. The February 2009 collision, five hundred miles above Siberia, was the first impact at high-speed involving two intact spacecraft - a derelict Russian satellite and a working American Iridium satellite.

The Iridium network consists of sixty six very fast moving communications satellites in relatively low orbit. Most communications satellites circle the planet in higher orbits, making collisions much less likely. The collision at 26,000 mph completely destroyed both the Kosmos 2251, a former military communications craft, weighing 2000 lbs, and the Iridium orbiter, which was 1235 lbs. The American satellite was operational at the time of the collision, but its Russian counterpart had been inoperative since at least 1995. The crash created debris clouds traveling at about 660 feet per second, between 300 and 800 miles above the surface of the Earth.

http://www.darkroastedblend.com/2009/03/one-in-million-collisions.html