Space may be big, really big, but Earth orbit is getting a bit crowded as space debris accumulates and threatens operational spacecraft. Riding aboard the last Dragon cargo mission to the International Space Station was part of the answer to this problem. NASA’s Space Debris Sensor (SDS) will be installed on the outside of the station, where it will spend the next two to three years monitoring debris between 5 mm to 0.5 mm in diameter to learn more about their characteristics.
Currently, there are over 1,400 operational satellites orbiting the Earth at distances from a few hundred to tens of thousands of miles above the planet. Over the past 60 years since the first Sputnik, our civilization has become completely dependent on these satellites. Without them, everything from the internet to commerce to national defense would be crippled overnight. Today, we depend on satellites for much of our long-distance communications and data transmission, weather monitoring, navigation, defense reconnaissance and many scientific investigations.
The problem is that over the decades many of these satellites have died and the rockets that launched them into space are also often in orbit, along with a great deal of miscellaneous space debris. This miscellaneous junk is the result of spacecraft breaking apart, including booster upper stages shredding themselves after over-pressurizing their tanks or the propellant inside vaporized, satellites blowing up when their discharged batteries generate volatile gases and droplets of solidified metal coolants from old Soviet nuclear-powered satellites.
According to NASA, there’s over 170 million items of debris ranging from discarded boosters to flecks of paint. In all, there are over 5,500 tonnes of debris circling the Earth with 98 percent made up of 1,500 objects in low Earth orbit. These include not only dead satellites and boosters, but a glove lost by US astronaut Ed White during his historic Gemini 4 spacewalk in 1965, a camera lost by Michael Collins on the Gemini 10 mission in 1966 as well as another lost by Sunita Williams of STS-116, a thermal blanket lost during STS-88 in 1998, 15 year’s worth of rubbish bags from the Russian Mir space station, a pair of pliers, a US$100,000 tool bag and the ashes of Star Trek creator Gene Roddenberry.
The potential damage from this debris as it travels at about 22,000 mph (35,400 km/h) is huge with even particle as small as 3 mm posing a threat to manned and unmanned spacecraft.
“Debris this small has the potential to damage exposed thermal protection systems, spacesuits, windows and unshielded sensitive equipment,” says Joseph Hamilton, the SDS project principal investigator. “On the space station, it can create sharp edges on handholds along the path of spacewalkers, which can also cause damage to the suits.”