Kessler Syndrome

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The Kessler Syndrome is a scenario, proposed by NASA consultant Donald J. Kessler, in which the volume of space debris in Low Earth Orbit is so high that objects in orbit are frequently struck by debris, creating even more debris and a greater risk of further impacts. The implication of this scenario is that the escalating amount of debris in orbit could eventually render space exploration, and even the use of satellites, too prone to loss to be feasible for many generations.

The Kessler Syndrome is especially insidious because of the "domino effect." Any impact between two objects of sizable mass will create additional shrapnel debris from the force of collision. Each piece of shrapnel now has the potential to cause further damage, creating even more space debris. With a large enough collision (such as one between a space station and a defunct satellite), the amount of cascading debris could be enough to render Low Earth Orbit essentially impassable.

Every satellite, space probe and manned mission has the potential to create space debris. As the number of satellites in orbit grow and old satellites become obsolete, the risk of a cascading Kessler Syndrome becomes greater.

The Kessler Syndrome presents a unique problem to human space travel. Space debris is very difficult to deal with directly, as the small size and high velocities of most debris would make retrieval and disposal impractically difficult. Given thousands of years, most debris in Low Earth Orbit would eventually succumb to air resistance in the rarefied atmosphere and plunge to the Earth. If magnetically susceptible, the debris could fall in a few decades due to the drag of the Earth's magnetic field.

To minimize the chances of damage to other vehicles, designers of a new vehicle or satellite are frequently required to demonstrate that they can be safely disposed of at the end of its life, for example by use of a controlled atmospheric reentry system.

Fortunately at the most commonly used Low Earth Orbits residual air drag helps keep the zones clear. Altitudes under 300 miles will be swept clear in a matter of months.