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Science Space Junk: Maybe we need Andy Griffith’s Salvage 1?
Science Space Junk: Maybe we need Andy Griffith’s Salvage 1? | Space Junk: Maybe we need Andy Griffith’s Salvage 1? |
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| by William Atkins | |
| Friday, 18 April 2008 | |
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Science DiscussionsSpace junk, sometimes also called space debris, space waste, or orbital debris, are the objects that remain in orbit about the Earth from past human ventures into space, whether they be manned or unmanned expeditions. They consist of spent rocket stages, antique satellites that no longer function, cameras, gloves, garbage bags, toothbrushes, paint flakes, coolant, dust, and other such materials. These pieces of space junk are a major concern for space agencies around the world because of the possible collisions they may have with active satellites and current space missions. The International Space Station, for instance, is armor plated to minimize the possibility of damage from space junk, along with micrometeorites. In fact, the NASA commander of the STS-48 mission in September 1991 had to perform an unplanned maneuver in order to avoid a near-collision with debris from the Cosmos 955 satellite Most of the space junk still in orbit about the Earth is in low Earth orbit (LEO), but some of it exists in geosynchronous orbit. The European Space Agency (ESA) recently announced that over twelve thousand objects are now trackable by humans on Earth while they orbit around the Earth. The ESA states that about 11,500 objects are in a range of altitudes of 500 to 930 miles (800 to 1,500 kilometers). Another 1,146 pieces are in geostationary orbit, at an altitude of about 22,240 miles (35,785 kilometers). Currently, geostationary satellites are usually raised to a “graveyard” orbit instead of de-orbiting them back to Earth. A graveyard orbit is a few hundred kilometers in altitude above their operational orbit. They are less of a danger to functioning satellites and space missions at this graveyard orbit. It costs much less (in fuel) to raise them than to deorbit them. It is estimated that a burn of about 5,000 feet (1,500 meters) per second is needed to take a satellite from geostationary orbit and to deorbit it to Earth. On the other hand, only one-hundredth the size of burn--about 36 feet (11 meters) per second--is needed to raise it to a higher graveyard orbit. Officials with the ESA state that about six hundred working satellites are now in orbit about the Earth. Each year about two hundred more pieces of space junk are added to our garbage dump in space. Without an active system to deorbit these objects, pieces in LEO can stay circling the Earth for tens, maybe hundreds, of years. The United States Strategic Command keeps a catalogue of about 13,000 objects orbiting the Earth. Its personnel’s efforts are mostly to prevent countries from thinking a piece of space junk is really a missile. According to the ESA Meteoroid and Space Debris Terrestrial Environment Reference-2005 model, there are more than 600,000 objects larger than 0.4 inch (one centimeter) in length in orbit about the Earth. An ESA computer generated image of space junk circling Earth is found at the Telegraph.co.uk website “Spacejunk in Earth’s atmosphere Revealed," just to get a perspective on the amount of junk out there in space. In other close-call incidents, in 2006, an Latin American Airbus, with 270 passengers onboard, flew very close to debris from a Russian spy satellite that was descending through the atmosphere of Earth over the Pacific Ocean. In July 1979, the largest piece of space debris, Skylab, came down and many pieces of the 78-ton space station landed along a ground track on the Australian Outback. Some techniques have been suggested or even implemented. Please read on. |
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