Sometime Friday afternoon, the six people—including two Americans—aboard the International Space Station got a warning: Head into the nearest Russian Soyuz spacecraft and wait for further instructions, because a chunk of a disabled Russian rocket was hurtling towards them at speeds of over 17,000 miles per hour.
The threat of man-made space debris is increasingly becoming a problem for astronauts and the nearly 700 satellites orbiting earth. NASA estimates there are about 19,000 man-made objects orbiting earth—at orbital speeds, even a tiny particle can destroy satellites or cause serious damage to the space station.
Early Saturday morning, the six astronauts got the all-clear—the errant piece of space garbage passed about 7 miles from the station, according to Kelly Humphries, a NASA spokesman. It was the third time in the past 11 years that astronauts have had to take shelter from space debris. Last June, a piece of space junk came about 1,000 feet from striking the station.
The problem, experts say, is that there's no good way to remove debris from orbit, and any collision, such as one between a $55 million American satellite and an inactive Russian satellite in 2009, can create thousands of new pieces of lethal debris.
"There's no solution—just don't generate new debris," General William Shelton, head of the Air Force Space Command, told reporters last week. "If you look at the problem of trying to clean up debris, the physics just don't close. With what we know about propulsion, there's no way to get there."
Switzerland has announced plans to try to bring inactive satellites back to earth, but NASA is skeptical that they'll be successful.
"There are a number of people studying the problem," Humphries says. "But there does not appear to be a realistic solution."
Shelton says the pieces of debris that are too small to track are often the most dangerous.
"If you can't sense it, you can't avoid it," he said. "If you think about something relatively small in mass, at orbital velocity, that is lethal to a fragile spacecraft."
What the U.S. Strategic Command can do, however, is get better at detecting space junk. Stratcom informed NASA of the imminent threat to the International Space Station too late to perform an evasive maneuver. Humphries says NASA needs about a 72-hour warning to have enough time for astronauts onboard to initiate an evasive maneuver—otherwise, they head onto the docked Russian Soyuz spacecraft.
"The Soyuz remains in orbit on the space station—it's used as their normal return vehicle, but it's available as a life boat as needed," he says.
The United States and other countries have discussed trying to create a space "Code of Conduct" to prevent countries from creating new debris. In 2007, China destroyed an out-of-commission satellite in order to test an anti-satellite weapon, creating at least 2,000 trackable pieces of debris and tens of thousands of smaller particles. Those pieces will continue to orbit earth for decades, before finally falling back to earth. With the pieces circling 600 miles above earth, they can remain in orbit for more than 100 years, according to NASA.
Shelton said that the military is developing a new system for detecting space junk, set to go live in 2017, that will hopefully give NASA more time to react in the future.
"It'll go from tracking basketball-sized objects to baseball-sized objects, and we'll have a much better idea of the entire debris field," he said. But when Stratcom has to issue an alert, "it's one of those situations where you just kind of tense up."