In one of this fall’s most anticipated blockbusters, Gravity, an astronaut duo played by George Clooney and Sandra Bullock are left adrift in space after their shuttle is destroyed. The culprit is Hollywood’s newest villain: space debris. Unfortunately for present day astronauts, this is not just Hollywood’s febrile imagination at work. As innocuous as it may sound, space debris is extremely hazardous and could even be lethal. In fact, the National Aeronautical Space Administration (NASA) has initiated an entire program, the Orbital Debris Program Office, dedicated to studying and monitoring this man-made phenomena. The international community, including the European Union and United Nations, has meanwhile been pursuing resolutions to mitigate and reduce space debris.
Orbital Debris: Just Trash?
NASA classifies space debris into two groups: natural (meteoroid) and artificial (man-made) particles. Most artificial debris is found in orbit around the Earth; hence it is called orbital debris. NASA further defines orbital debris as “any man-made object in orbit about the Earth which no longer serves a useful function.” This includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris and fragmentation debris.
Presently, both the Department of Defense (DOD) and NASA track orbital debris as miniscule as 2 inches (5 centimeters) in size. Per NASA estimates, there are more than 500,000 pieces of debris larger than a marble and up to 20,000 pieces larger than a softball floating around the Earth’s atmosphere. This debris is incredibly dangerous as it whizzes in orbit at speeds in excess of 17,500 mph. At these velocities, even the smallest piece could incapacitate a satellite or spacecraft.
As early as the 1970s, scientists working on both the U.S. and Russian space programs were becoming increasingly alarmed by the exponential growth of orbital debris. NASA’s Donald J. Kessler studied the potential dangers of colliding space debris. In what was later dubbed the “Kessler Syndrome,” he postulated that the volume of space debris increases with the number of launches, especially in the low Earth orbit (LEO). Over time, the density of debris will increase, causing collusions that produce even more debris. Often, this debris will fall harmlessly to Earth. But Kessler believed the remainder could ultimately form a “debris belt” around the Earth that would inhibit space travel. A 2008 report by the Council on Foreign Relations concluded that orbital debris is like radioactive fallout after a nuclear detonation because it can linger for many years.
Currently, the LEO has the highest concentration and rate of growth of debris than any other orbit. Debris concentrations more than doubled in the LEO between 2004 and 2009. There are myriad reasons why the LEO is a preferred orbit but one of the most important is that it is good for Earth observation missions (weather, intelligence and communications satellites). Most satellites operate on Sun-synchronous orbits in this region at altitudes of between 370 to 560 miles (600 and 900 km). As a result, this is also the orbit where the most collisions occur. The UN’s Office of Outer Space Affairs Committee on the Peaceful Uses of Outer Space draft report in 2010 notes that the first collision in this region occurred on February10, 2009 between an Iridium-33 (U.S.) and Cosmos-2251 (Russian) satellite. This event alone produced more than 2,200 traceable items.
The emergence of a new player in space complicates the issue. With China’s first successful satellite launch in 1970, the advent of manned spaceflight in 2003 with astronaut Lang Liwei, a proposed Moon rover launch by the end of this year and the planned Tiangong-2 (Heavenly Palace-2) space lab to debut around 2015, the volume of orbital debris is expanding rapidly. This amplification of the “Kessler Syndrome” threatens not only the international community’s stellar assets but also Chinese ones as well, including the safety of their astronauts, commonly referred to as taikonauts.