For the second time in less than three weeks, the International Space Station has had to swerve to avoid running into space junk.

The National Aeronaytics and Space Administration said the station -- a joint venture between the space agencies of the United States (NASA), Russia, Japan, Europe and Canada -- fired its thrusters Thursday, April 3, to move up about half a mile, in order to avoid floating parts from an old Ariane 5 rocket. The European Space Agency launches Ariane rockets from South America.

If the station had not veered from its prior trajectory, the Ariane junk could have passed within 1,040 feet of the outpost, maybe even less, according to a report by the Associated Press.

NASA announced the station's six-man crew was never in danger.

NASA spokesman Kelly Humphries said the space agency has had to change course dozens of times to keep from being hit by since the orbiting laboratory was established in 1998. Humphries added that sometimes plans to swerve the station away from debris were underway, but then cancelled at the last moment.

The ISS had to maneuver away from the orbiting remains of an old Russian weather satellite March 16.

Space debris includes both natural meteoroids, which are orbiting the sun, and artificial, or, man-made, particles, in orbit about Earth -- which is why the latter is typically called orbital debris.

Including just about any type of material that no longer serves a useful function, orbital debris can be nonfunctional spacecraft, abandoned launch vehicle stages and mission-related parts or fragments.

There are more than 20,000 pieces of debris larger than a softball orbiting the earth, traveling at speeds of up to 17,500 mph, according to NASA data.

There are also at least 500,000 known pieces of debris the size of a marble or larger orbiting the planet, as well as millions of other pieces so small they can't be tracked.

Even minuscule flecks of paint can potentially damage a spacecraft when traveling as fast as the space junk does. A number of space shuttle windows had to be replaced because of damage from particles discovered to be paint flecks.

As such, NASA says it takes the threat of collisions with space debris extremely seriously and has had a long-standing policy in place on how to deal with each potential collision threat.

"The greatest risk to space missions comes from non-trackable debris," said Nicholas Johnson, NASA chief scientist for orbital debris.