In more than 40 years of space travel, man has turned outer space into a junkyard, dropping hundreds of thousands of objects into high-speed orbit around Earth.
Broken satellites. Lens caps. Exploded rockets. Flakes of brittle paint.
Scientists have warned for years that the garbage poses a growing threat to the spaceflights. Now, NASA is investigating whether the debris may have caused or contributed to the breakup of Columbia.
“They are always among the things that are the greatest risks,” said George Gleghorn, a former engineer who co-authored a 1995 report on orbital debris for NASA.
But the report assessed the risk of a spacecraft being hit by flying debris as minute.
“You’re much more likely to be struck by lightning than by space debris,” Gleghorn said.
Still, his committee echoed the concerns of another report published six years earlier that scientists did not understand space debris well enough to dismiss the hazard.
“Objects much smaller than those presently cataloged can destroy a spacecraft in a collision,” noted a summary statement on the report. “Even collisions that do not destroy a spacecraft can degrade its performance or cause it to fail.”
Today, rocket scientists take space trash seriously.
The Air Force Space Command tracks daily more than 9,500 Earth-orbiting objects, which range in size from baseballs to a basketball court. Scientists plot the course of launching orbiters around these trails of circling debris.
But Earth telescopes cannot see hundreds of thousands of trash particles — some as small as grains of sand — moving fast enough to produce catastrophic crashes.
“We can’t track it, and yet it’s moving so fast that it has a lot of kinetic energy, and so it has the potential to do a lot of damage,” said John Lindner, an associate professor of physics at Wooster College in Ohio and an expert in space debris.
Routinely, NASA engineers have to replace windows pocked with the imprints of space particles that flew into the shuttle.
In 1996, Columbia returned from a mission with damaged windows and scientists later found 51 pits in them, according to NASA incident reports.
Experts agreed that it was possible, if not probable, that a piece of trash could have struck Columbia somewhere along its doomed flight path.
The impact could have caused irrevocable damage to the protective surface of the space shuttle — or injured a fragile piece of equipment around the left wing.
Though it seems unlikely, they said, astronauts engrossed in research inside the noisy cabin, which can be like living on a top of a busy expressway, might have been unaware of what had happened.
“It would be very easy not to notice some goofy thing that happened that was not expected,” said Harvey Wichman, who runs the Aerospace Psychology Laboratory at Claremont McKenna College in California and designs spacecraft interiors.
There has even been speculation that on re-entry, Columbia might have struck decaying debris raining down from Earth’s atmosphere.
“That is just the most outrageously bad luck you can have,” said Wichman, who doubted that was the case. “You can’t guard against something like that.”
If space debris were found to have contributed to the Columbia disaster, it would accelerate efforts to clean up space.
Eight years ago, NASA scientists studied a proposal by Claude Phipps of Phontonic Associates to design a laser capable of shooting down orbital debris. Phipps calculated that his Orion Project laser could blast away 80 percent of the debris in orbit in two years.
“Space is a very dangerous place for an astronaut to be out there spacewalking,” said Phipps, who is still waiting for federal funding. “The odds are very small. He could be out there walking 100 years. But one day, it will happen.”
