By Traci Watson, USA TODAY
Getting rid of space station's junk a mission of its own
NASA's on a littering spree.
Astronauts on the International Space Station have been hurling more garbage out the station's back door in recent months. Outdated equipment — some of it expensive — that's not practical for the space shuttle to bring back to Earth is simply being thrown into space.
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If all goes according to plan, the junk falls into the Earth's atmosphere and burns up within months or even weeks. NASA needs to plan carefully so the trash won't hit anything, such as the space station or a visiting space shuttle.
As early as April, astronaut James Reilly is scheduled to go on a spacewalk outside the space station and toss five unneeded sun-protection covers over the station's edge. On a spacewalk at the station later this year, astronaut Clay Anderson plans to heave an obsolete, $10 million storage tank the size of a refrigerator.
Astronauts need to be careful about their aim. A piece of junk that goes in the wrong direction could, in a worst-case scenario, slam into the station or into a space shuttle visiting the orbiting laboratory. That could damage costly equipment or even endanger the crew's lives.
Astronauts also need to put just the right amount of muscle into their pitch. If they don't get the junk flying fast enough, Mission Control would have to fire the station's jets to move the lab out of the debris' path. That consumes precious rocket fuel, needed to keep the station at the right altitude.
NASA policy says using space as a dumping ground will not become standard practice.
"It's really only a measure of last resort," says Nicholas Johnson, head of NASA's orbital debris program. "We don't want to create debris even if it's short-lived, unless it's overwhelmingly necessary."
One alternative: pack trash into the shuttle and return it to Earth. Another option: load it onto a Russian cargo ship, which then undocks from the station and burns up in the atmosphere.
Those methods require a spacewalking astronaut to lug trash inside the station, so it can be loaded later onto the shuttle or the Russian cargo ship. That's difficult for bulky items such as the storage tank, which is also a menace because it holds toxic chemicals.
As a result, "the additional time and additional risk" of hauling trash into the station sometimes "outweighs any risk of simply letting them go," Johnson says.
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The exact angle and force of an astronaut's pitch depend on an object's density and size, which dictate how fast it falls out of orbit and into the atmosphere. Johnson says it's easy for the spacewalking junkmen to hurl something with the right speed and in the right direction.
Anderson hopes so.
"I want to make sure it doesn't tumble too much," the avid softball player says of his throw, which he'll make after the station's robotic arm takes him on a 20-minute ride to a disposal spot.
After astronaut Michael Lopez-Alegria shoved several sun-protection shields off the station last month, he didn't conceal his pride in his performance. "Right over the plate," he told Mission Control.
NASA is still refining the procedures to make sure each trash-tossing is safe. Just a few days before Lopez-Alegria was supposed to shove another cover, engineers on the ground discovered an error in their safety analysis. If Lopez-Alegria had thrown the cover as planned, it might have struck the station.
Instead, he took it inside the station to await another means of disposal. NASA will do some of its double-checking earlier, says deputy station manager Kirk Shireman.
When a disposal effort does go well, it's "a lot of fun," says astronaut William McArthur, who tossed a $1 million electric-charge sensor in 2005.
"Maybe it's like the first time you ever parallel-park a car," he says. "Until you've actually done a physical task, there are doubts."
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