Kessler Syndrome and Networked Space Debris
Kessler Syndrome is the process in which objects in Earth’s orbit collide with space debris, creating a cascading effect that exponentially increases the rate of further collisions. In the worst case scenario, the fulfillment of Kessler Syndrome would create such a dense field of debris surrounding Earth that rocket launches would be nigh-impossible, as any spacecraft leaving the atmosphere would be annihilated. Each object in Earth’s orbit carries with it a huge amount of force due to its incredibly high speed. According to NASA, “space junk” can have speeds of “up to 17,500 mph.” If a manned spacecraft was penetrated by a small piece of orbital debris, it could cause instantaneous depressurization and potentially kill the entire crew. The 2007 test of a Chinese anti-satellite missile caused the breakup of a satellite in high Earth orbit, further adding to the fear of the beginnings of a Kessler Syndrome level increase. Space.com claims that the test created 950 trackable pieces of debris alongside 35,000 pieces larger than a centimeter. The cloud extends “less than 125 miles (200 kilometers) to more than 2,292 miles (3,850 kilometers), encompassing all of low Earth orbit”. This is obviously an important issue, but how exactly is it related to networks?
For scientists to monitor trackable space debris, a network model is needed. A strong edge between two nodes could be defined as being within a certain distance, as the chance of a collision between the two objects is fairly high. A weak edge would be a greater distance away, while if there would be almost no situation in which two nodes could collide, they would not be connected. This would allow scientists to predict the likelihood of cascading collisions in certain regions of space with denser fields of strong edges. Using future methods of space cleanup, we could focus on those areas of space in order to most efficiently slow the effects of Kessler Syndrome. There is also the possibility of timing rocket launches to coincide with areas of weak or no edges. The Space Surveillance Network (Run by the Department of Defense and NASA) mapping of space debris is “divided into three categories depending upon size of threat. For objects 4 inches (10 centimeters) and larger, conjunction assessments and collision avoidance maneuvers are effective… Objects smaller than this usually are too small to track and too large to shield against. Debris shields can be effective in withstanding impacts of particles smaller than half an inch (1 centimeter).” Currently, NASA uses the Space Surveillance Network to predict if any debris will be within 30 miles of a spacecraft. If the network is accurate enough, there is sufficient time to maneuver. In the event of a puncture, astronauts board the Soyuz and return to Earth.
This is an excellent illustration of where network theory can be useful in real life applications. A proper utilization of a debris field network would make space travel safer and more reliable, as well as slowing the effects of Kessler Syndrome in targeted debris cleanup.
Sources:
http://www.space.com/3415-china-anti-satellite-test-worrisome-debris-cloud-circles-earth.html
http://www.nytimes.com/2007/02/06/science/space/06orbi.html?pagewanted=2
http://www.nasa.gov/mission_pages/station/news/orbital_debris.html