Utilizator:Jobava-ro/ciorne/Gunoi spațial
From Wikipedia, the free encyclopedia
Space debris, also known as orbital debris, space junk and space waste, is the collection of defunct objects in orbit around Earth. This includes spent rocket stages, old satellites and fragments from disintegration, erosion and collisions. Since orbits overlap with new spacecraft, debris may collide with operational spacecraft.
As of 2009[update] about 19,000 pieces of debris larger than 5 cm (2 in) are tracked,[1] while an estimated 300,000 pieces larger than 1 cm exist below 2.000 kilometri (1.200 mi).[1] For comparison, the International Space Station orbits in the 300–400 kilometri (190–250 mi) range and the 2009 satellite collision and 2007 antisat test events occurred at from 800 la 900 kilometri (500 la 560 mi).[1]
Most space debris is smaller than 1 cm (0,4 in), including dust from solid rocket motors, surface-degradation products (such as paint flakes) and frozen coolant droplets released from RORSAT nuclear-powered satellites. Impacts by these particles cause erosive damage, similar to sandblasting, which can be reduced by the addition of ballistic shielding (such as a Whipple shield, used to protect parts of the International Space Station) to a spacecraft. Not all parts of a spacecraft can be protected in this manner; solar panels and optical devices such as telescopes or star trackers are subject to constant wear from debris and micrometeoroids. Below 2.000 kilometri (1.200 mi), the flux from space debris is greater than that from meteoroids.[1] Decreasing risk from space debris larger than 10 cm (4 in) is often obtained by maneuvering a spacecraft to avoid a collision. If a collision occurs, the resulting fragments can become an additional collision risk.
Since the chance of collision is influenced by the number of objects in space, there is a critical density where the creation of new debris is theorized to occur faster than natural forces remove them. Beyond this point a runaway chain reaction (known as the Kessler syndrome) may occur, rapidly increasing the amount of debris in orbit and the risk to operational satellites. Whether the critical density has been reached in certain orbital bands is a subject of debate.[2] A Kessler syndrome would render a portion of useful polar-orbiting bands difficult to use, increasing the cost of space missions. The measurement, growth mitigation and potential removal of space debris are conducted by the space industry.