space_junk_010514 Spacecraft and launch vehicles need urgent safety modifications in light of a growing
sea of orbiting debris from 30 years of spaceflight, a group of Russian scientists say. Some 9,000 catalogued nuts, bolts and other objects create a ring of debris around Earth, and the researchers say many of these things will be there for hundreds, or even thousands of years.
Space shuttles, the International Space Station (ISS) and Mir have all taken evasive actions to avoid space debris, and a French satellite was once destroyed after a collision. The risk of a dangerous collision with a space object is 5 to 10 percent within the 15-year estimated operation period of the ISS, the researchers say in a press release issued by the Russian science news agency Informnauka last week.
But the cost of designing safe ships will challenge engineers, the researchers say.
What's up there?
The fate of an object in space depends on its altitude. In the general neighborhood of the International Space Station, around 250 miles (400 kilometers) up, enough atmosphere exists to slow junk down and force a reentry, often within two years or so. But higher up, things hang around longer.
The scientists found that objects are concentrated at about 500 miles (800 kilometers) up, and again at 930 miles (1,500 kilometers). Another group of objects is located in geostationary orbit, about 22,300 miles (35,900 kilometers) above Earth, where important communication and weather satellites orbit in perches fixed over a given spot on the ground. At this altitude, there is not enough atmospheric drag to tug at space debris and pull it down.
Generally, space debris can be divided into two categories: objects that can be seen through a telescope -- roughly 9,000 objects 8 inches (20 centimeters) or larger -- and those too small for regular observations.
A 1999 study estimated there are some 4 million pounds (1.8 million kilograms) of space junk in low Earth orbit, just one part of a celestial sea of roughly 110,000 objects larger than 0.4 inch (1 centimeter) -- each big enough to damage a satellite or space-based telescope.
These smaller particles, including paint chips and other bits of debris down to a few millimeters in size, can spoil a solar battery or punch a hole in a fuel tank. But these objects are too numerous to count.
Looking ahead
Scientists involved with the ISS are developing simulators that allow them to forecast the behavior of such small objects. Applying their model, the specialists from the Russian Aviation and Space Agency's Center for Space Observations in Russia have investigated how the space pollution problem may develop.
They have reviewed five scenarios:
- Everything remains unchanged.
- The number of rocket explosions, which create much of the debris, is reduced by half.
- The number of carrier rockets in space is reduced by half.
- All (or half) of the satellites and carrier rockets return to Earth.
- All of the above measures are taken simultaneously.
In the case of scenarios one through three, the debris volume in orbit will increase two to three times by the 22nd century. Provided all the above steps are implemented -- the number of explosions goes down and all flying objects return to Earth -- debris volume would be reduced by 1.5 times within the next 100 years.
At a March meeting of the International Committee on Space Contamination, a resolution was adopted regarding the necessity to bring order to the region of space where satellites and stations orbit. The spaceflight standards for all countries should include a requirement for the space device developers to ensure
, the resolution states.Because of costs, however, the Russian researchers say there is no way to achieve this goal. First of all, it is necessary to change the carrier rockets' design so that the waste stages descend to the lower orbits, where they will reenter. Secondly, additional fuel will be needed for each satellite to allow its descent to the atmosphere.
But the space debris problem "is close to critical, so these expenses appear to be unavoidable," the researchers said in the press release.
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