Why NASA Is So Concerned About Space Junk

It’s only the size of a nut or a bolt. It could be a piece of tinfoil or a paint chip. Or it might be a loose screw.

In ordinary circumstances, one of these would never be expected to injure or endanger anyone. But then being in orbit circling the Earth in a giant fuel-laden combustible vehicle isn’t considered an ordinary circumstance.

If you’re wondering why NASA is being so careful about the space junk it believes emanated from the shuttle, you’re not alone. It’s easy to think that in the vastness of space, a small piece of detritus wouldn’t be enough to hit anything.

But space experts contend the chances of it happening are greater than most of us Earth-bound observers would like to think. Space may not have any atmosphere, but it’s filled with dust, particles and floating rocks, all drifting aimlessly in the airless void.

If any of them hit a sensitive and expensive space vehicle with even a slight force, there’s always the risk of damage. A 2003 NASA study estimated that space garbage hitting an orbiter accounts for at least half of all the dangers astronauts will experience while floating above the planet.

And according to the NASA website, any collision can be enough to cause serious concern.

“The average impact speed of a piece of orbital debris colliding with another object is 10 km/s   or 36,000 km per hour,” it warns. “Because of the great speeds involved, a piece of orbital debris does not need a lot of mass to have substantial force at impact. To generate the same force as a 1,500 kilogram (3,300 lbs.) car traveling at 97 km/h. a piece of debris would only have to be 4 kg (8.8 lbs.) in mass.”

Scientists keep strict track of what’s around the shuttle and the international space station and generally try to steer the various craft around them. The shuttle also orbits in a backward position whenever possible to protect its most vulnerable parts – like its heat tiles or its windows.

Mission control will order a maneuver when there’s a 1 in 10,000 chance of a collision, which they claim happens about once every two years.

In some cases, the debris hits with only minor damage, few have enough energy to penetrate the hull of a ship and none have ever hit an astronaut on a spacewalk.  

But the natural stuff isn’t the only problem.

NORAD has tracked thousands of bits of space junk that are manmade, including pieces of abandoned satellites, materials lost from previous flights, foam, and other flotsam and jetsam that comes off during the unpredictability of a mission.

And NASA says it’s happened before.

“The space shuttle frequently returns to Earth with tiny impact craters from being hit by orbital debris,” the agency reports.

 “Astronauts have reported seeing very small cracks formed in the shuttle’s front windows when they strike objects. While impact by small pieces of orbital debris is routine, the odds of two pieces of debris larger than 10 cm in diameter colliding is very low. In all of spaceflight history, there is only one recorded incident of two such objects from different missions accidentally colliding.”

But with the last shuttle accident that killed the entire crew, no one’s willing to leave anything to chance.

So when will all that garbage come home to roost? Scientists say it all depends on where it is.

Debris in an orbit 600 kilometres above us takes several years to fall back to Earth and much of it burns up in the atmosphere.

Junk that’s 800 kilometres or more takes roughly a decade.

And anything in the 1,000 km range or higher may not make a re-entrance in our lifetime. NASA says it could be floating up there for at least a century.