The Kessler Syndrome: A World Without Satellites
By Jordan Liew, Staff Contributor
When politicians, scientists, and activists talk about pollution and the environment, they are typically referring to the oceans, the rivers, the soil, or the air. But what about space? Can that vast black sea of stars become polluted, and is it even an environment that humans should care about? In fact, space— specifically Earth’s orbit—is massively polluted already. Although there are around 1,000 functional satellites in space, there are more than twice as many (around 2,600) derelict and decommissioned satellites. Some 34,000 objects larger than ten centimeters have been observed by radar or telescope. For objects between one and ten centimeters, that number jumps up to over half a million. Debris less than one centimeter in size exist in the millions. In short, Earth is surrounded by a huge cloud of space junk.
So why is all this space debris a problem? Why would a loose screw or a fleck of paint floating around in space be so dangerous? The answer lies in the speed at which space debris circles the Earth. Orbital debris can travel at speeds of up to 17,500 miles per hour. Even something as small and soft as a paint fleck can damage spacecraft or satellites when moving at such velocities. In fact, NASA has been forced to replace many space shuttle windows damaged by paint flecks. If a larger, ten-centimeter piece of space debris was to collide with something like the International Space Station, the damage would be potentially catastrophic.
The danger of space debris, however, is not just in its capacity to punch a hole through a space vehicle or satellite; it is the fact that space debris collisions create more space debris. Unlike on Earth where the debris from something breaking apart is pulled to the ground by gravity and rendered inert, when a satellite is destroyed by space debris, those pieces will continue to hurtle around the planet at incredible speeds. This was demonstrated in 2007 when the Chinese tested an anti-satellite weapon on the defunct Fengyuan-1C weather satellite. As a result, more than 3,000 pieces of debris were added to Earth’s orbit—the largest addition of space debris from any single event. Then, in 2009, the defunct Russian satellite, Kosmos-2251, crashed into Iridium-33, an American telecommunications satellite, which contributed another 2,000 pieces of debris into orbit.
“As space debris accumulates in Earth’s orbit, it becomes increasingly likely that the debris will collide with each other and other objects, resulting in exponential growth in space debris.”
Astrophysicist and former NASA scientist Donald Kessler predicted this exact phenomenon in 1978. Shortly thereafter, a fellow astrophysicist, John Gabbard, coined the term Kessler Syndrome to describe this cascading effect. According to Donald Kessler, it is possible that the debris cloud will eventually grow so large as to prevent future operations within Earth’s orbit. That would translate into a future without weather forecasts, telecom, satellite-assisted navigation, or research satellites.
Since Donald Kessler’s paper, NASA and the Department of Defense have taken steps to mitigate the growth of space debris through sustainably-designed rockets that produce fewer or no debris when traveling to and from Earth’s orbit. Yet, even under the improbable scenario of introducing no further objects into orbit by halting all space launches, simulations indicate that the number of debris objects would still continue to grow.
Thus, proactive measures must be taken to reduce debris in Earth’s orbit lest it be rendered completely unusable by future generations. Donald Kessler has suggested that removing just five to ten inoperable satellites a year could halt the exponential growth of space debris. In recent years, a few plans have been suggested to proactively reduce space debris. For example, the Australian National University is developing a laser that can track, target, and destroy space debris. Likewise, the Japanese Space Agency (JAXA) has partnered with a private company to develop a massive 700-meter long aluminum and steel net to sweep up space debris. Other plans call for solar sails and various types of capture mechanisms such as robotic arms and space sling shots.
“It remains to be seen whether these novel and imaginative solutions will actually work.”
However, as demonstrated by China’s 2007 anti-satellite test and the 2009 collision, other countries may not care as much about further polluting Earth’s orbit, and accidents are always possible. Even in the United States, a decentralized space regulatory system creates enforcement difficulties. An effective mitigation strategy will require any future technologies to be governed by strong and dedicated international regulation and cooperation. But the difficulties of mitigating Earth’s pollution on-the-ground suggest that this will be no easy task.