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Kessler syndrome
The Kessler syndrome, also known as the Kessler effect, collisional cascading, or ablation cascade, is a scenario proposed by NASA scientists Donald J. Kessler and Burton G. Cour-Palais in 1978. It describes a situation in which the density of objects in low Earth orbit (LEO) becomes so high due to space pollution that collisions between these objects cascade, exponentially increasing the amount of space debris over time. This proliferation of debris poses significant risks to satellites, space missions, and the International Space Station, potentially rendering certain orbital regions unusable and threatening the sustainability of space activities for many generations. In 2009, Kessler wrote that modeling results indicated the debris environment had already become unstable, meaning that efforts to achieve a growth-free small debris environment by eliminating past debris sources would likely fail because fragments from future collisions would accumulate faster than atmospheric drag could remove them. The Kessler syndrome underscores the critical need for effective space traffic management and collision avoidance strategies to ensure the long-term viability of space exploration and utilization.
Willy Ley predicted in 1960 that "In time, a number of such accidentally too-lucky shots will accumulate in space and will have to be removed when the era of manned space flight arrives". After the launch of Sputnik 1 in 1957, the North American Aerospace Defense Command (NORAD) began compiling a database (the Space Object Catalog) of all known rocket launches and objects reaching orbit: satellites, protective shields and upper- and lower-stage booster rockets. NASA later published[when?] modified versions of the database in two-line element set, and during the early 1980s the CelesTrak bulletin board system re-published them.
The trackers who fed the database were aware of other objects in orbit, many of which were the result of in-orbit explosions. Some were deliberately caused during the 1960s anti-satellite weapon (ASAT) testing, and others were the result of rocket stages blowing up in orbit as leftover propellant expanded and ruptured their tanks. To improve tracking, NORAD employee John Gabbard kept a separate database. Studying the explosions, Gabbard developed a technique for predicting the orbital paths of their products, and Gabbard diagrams (or plots) are now widely used. These studies were used to improve the modeling of orbital evolution and decay.
When the NORAD database became publicly available during the 1970s, NASA scientist Donald J. Kessler applied to the database of known objects a technique developed to study the asteroid-belt. In June 1978, Kessler and Burton Cour-Palais co-authored "Collision Frequency of Artificial Satellites: The Creation of a Debris Belt", demonstrating that the process controlling asteroid evolution would cause a similar collision process in LEO in decades rather than billions of years. They concluded that by about 2000, space debris would outpace micrometeoroids as the primary ablative risk to orbiting spacecraft.
At the time, it was widely thought that drag from the upper atmosphere would de-orbit debris faster than it was created.[citation needed] However, Gabbard was aware that the number and type of objects in space were under-represented in the NORAD data and was familiar with their behavior. In an interview shortly after the publication of the 1978 Kessler paper, Gabbard coined the term Kessler syndrome to refer to the accumulation of debris; it became widely used after its appearance in a 1982 Popular Science article, which won the Aviation-Space Writers Association 1982 National Journalism Award.
The lack of hard data about space debris prompted a series of studies to better characterize the LEO environment. In October 1979, NASA provided Kessler with funding for further studies. Several approaches were used by these studies.
Optical telescopes and short-wavelength radar were used to measure the number and size of space objects, and these measurements demonstrated that the published population count was at least 50% too low. Before this, it was believed that the NORAD database accounted for the majority of large objects in orbit. Some objects (typically, US military spacecraft) were found to be omitted from the NORAD list, and others were not included because they were considered unimportant. The list could not easily account for objects under 20 cm (8 in) in size—in particular, debris from exploding rocket stages and several 1960s anti-satellite tests.
Returned spacecraft were microscopically examined for small impacts, and sections of Skylab and the Apollo Command/Service Module which were recovered were found to be pitted. Each study indicated that the debris flux was higher than expected and debris was the primary source of micrometeoroids and orbital debris collisions in space. LEO already demonstrated the Kessler syndrome.
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Kessler syndrome
The Kessler syndrome, also known as the Kessler effect, collisional cascading, or ablation cascade, is a scenario proposed by NASA scientists Donald J. Kessler and Burton G. Cour-Palais in 1978. It describes a situation in which the density of objects in low Earth orbit (LEO) becomes so high due to space pollution that collisions between these objects cascade, exponentially increasing the amount of space debris over time. This proliferation of debris poses significant risks to satellites, space missions, and the International Space Station, potentially rendering certain orbital regions unusable and threatening the sustainability of space activities for many generations. In 2009, Kessler wrote that modeling results indicated the debris environment had already become unstable, meaning that efforts to achieve a growth-free small debris environment by eliminating past debris sources would likely fail because fragments from future collisions would accumulate faster than atmospheric drag could remove them. The Kessler syndrome underscores the critical need for effective space traffic management and collision avoidance strategies to ensure the long-term viability of space exploration and utilization.
Willy Ley predicted in 1960 that "In time, a number of such accidentally too-lucky shots will accumulate in space and will have to be removed when the era of manned space flight arrives". After the launch of Sputnik 1 in 1957, the North American Aerospace Defense Command (NORAD) began compiling a database (the Space Object Catalog) of all known rocket launches and objects reaching orbit: satellites, protective shields and upper- and lower-stage booster rockets. NASA later published[when?] modified versions of the database in two-line element set, and during the early 1980s the CelesTrak bulletin board system re-published them.
The trackers who fed the database were aware of other objects in orbit, many of which were the result of in-orbit explosions. Some were deliberately caused during the 1960s anti-satellite weapon (ASAT) testing, and others were the result of rocket stages blowing up in orbit as leftover propellant expanded and ruptured their tanks. To improve tracking, NORAD employee John Gabbard kept a separate database. Studying the explosions, Gabbard developed a technique for predicting the orbital paths of their products, and Gabbard diagrams (or plots) are now widely used. These studies were used to improve the modeling of orbital evolution and decay.
When the NORAD database became publicly available during the 1970s, NASA scientist Donald J. Kessler applied to the database of known objects a technique developed to study the asteroid-belt. In June 1978, Kessler and Burton Cour-Palais co-authored "Collision Frequency of Artificial Satellites: The Creation of a Debris Belt", demonstrating that the process controlling asteroid evolution would cause a similar collision process in LEO in decades rather than billions of years. They concluded that by about 2000, space debris would outpace micrometeoroids as the primary ablative risk to orbiting spacecraft.
At the time, it was widely thought that drag from the upper atmosphere would de-orbit debris faster than it was created.[citation needed] However, Gabbard was aware that the number and type of objects in space were under-represented in the NORAD data and was familiar with their behavior. In an interview shortly after the publication of the 1978 Kessler paper, Gabbard coined the term Kessler syndrome to refer to the accumulation of debris; it became widely used after its appearance in a 1982 Popular Science article, which won the Aviation-Space Writers Association 1982 National Journalism Award.
The lack of hard data about space debris prompted a series of studies to better characterize the LEO environment. In October 1979, NASA provided Kessler with funding for further studies. Several approaches were used by these studies.
Optical telescopes and short-wavelength radar were used to measure the number and size of space objects, and these measurements demonstrated that the published population count was at least 50% too low. Before this, it was believed that the NORAD database accounted for the majority of large objects in orbit. Some objects (typically, US military spacecraft) were found to be omitted from the NORAD list, and others were not included because they were considered unimportant. The list could not easily account for objects under 20 cm (8 in) in size—in particular, debris from exploding rocket stages and several 1960s anti-satellite tests.
Returned spacecraft were microscopically examined for small impacts, and sections of Skylab and the Apollo Command/Service Module which were recovered were found to be pitted. Each study indicated that the debris flux was higher than expected and debris was the primary source of micrometeoroids and orbital debris collisions in space. LEO already demonstrated the Kessler syndrome.
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