How will the Mir space station be deorbited?

When it was launched in 1986, the Russian Mir space station was only supposed to have a life span of about five years, but it proved to have more longevity than anyone expected. Feb. 20, 2001, marked the 15th anniversary of the station’s launch, but old-age has finally caught up with the spacecraft. Mir has been plagued by technical and structural problems, and in November 2000, the Russian government announced that it would destroy the space station.

The process of deorbiting the Mir space station has already begun. A Russian cargo ship, the Progress, was launched on Jan. 24, 2001, carrying twice its normal amount of fuel. The extra fuel has been used to fire the Progress’ thrusters and push the 137-ton station into a controlled descent through the Earth’s atmosphere.

The descent of Mir has been made in stages. The first firing of Progress’ thrusters dropped Mir from its original altitude of about 195 miles (315 kilometers) to an altitude of about 143 miles (230 km). Mir is now in a slow descent. When it reaches an altitude of about 135 miles (217 km) on Friday, March 23, Progress will fire its thrusters somewhere over Afghanistan and send Mir into the thicker layers of the Earth’s atmosphere. When the station reaches the thick layers of the Earth’s atmosphere at about 50 miles (80 km) above the Earth’s surface, the majority of the spacecraft will fall apart and burn up. Whatever pieces that are left of the station are expected to crash down into the South Pacific Ocean about 1,900 miles (3,000 km) east of New Zealand. It will take about 30 minutes between the time the station enters the atmosphere and the time it crashes into the ocean.

Russia has decided to dump Mir because the wear and tear that the station has endured over 15 years has made it unfit for further missions. The destruction of Mir will also delay the space tourism plans of MirCorp, a Dutch company that had planned to send a millionaire to Mir. One Russian official has said that the station is in such poor condition that it could fall into an uncontrolled deorbit at any moment. Additionally, Russia plans to concentrate more of its attention and money on the International Space Station Alpha, which is being built by a consortium of 16 countries.

Mir’s demise began when a fire that broke out on board the spacecraft in February 1997 was followed by a near-fatal collision with an unmanned cargo ship in June of the same year. Since then, Mir has experienced a series of technical and structural problems. Most recently, the Russian Space Agency lost contact with the space station for more than 20 hours in December 2000.

While Russian officials have promised that Mir will be brought down out of orbit safely, the process of bringing spacecraft out of orbit does not always go as planned. In 1978, Russia deorbited a satellite that flew out of control, crashing into northern Canada. No one was hurt by the crash, but radioactive fragments were strewn over the wilderness. A year later, the U.S. had similar problems when Skylab unexpectedly fell from orbit into an uncontrollable descent. The spacecraft crashed into Western Australia. Chunks of debris were scattered across the countryside, some pieces weighing as much as 1,800 pounds (816 kg). Again, no one was injured, but it showed the need for better deorbiting technologies for unmanned spacecraft.

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