The troubled Mir spacecraft could land on populated areas when it ends its 13-year endurance trial in orbit, say British scientists.
Russian scientists plan to nudge the elderly space hotel and laboratory into the atmosphere and lose it in the Pacific Ocean at the end of next year, but British experts warn that it could hit populated areas instead."The trouble is that Mir is a very complex vehicle," said Richard Crowther, a space scientist at DERA, Britain's defense research agency. "It's very easy to de-orbit a vehicle such as the shuttle, which has well-defined and symmetric aerodynamic surfaces.
"The problem with the Mir station is that it is asymmetric and it is difficult to predict how such a shape would behave when it gets into the lower reaches of Earth's atmosphere. Unlike the shuttle, which has rigid surfaces, the Mir station has solar arrays which will bend and buckle quickly."
The last NASA astronaut on Mir, Andrew Thomas, has checked out, leaving only a Russian crew. Moscow space chiefs may decide they can't afford to supply the space station for much longer. Mir's managers plan to let it sink gradually closer to Earth and then in December 1999 help the last supply ship nudge it into the atmosphere on a trajectory that will let it splash down harmlessly.
Crowther said that once Mir had been pushed into the atmosphere, it would be difficult to control its terminal trajectory. Mir would come streaking from the heavens at a shallow angle at 17,500 mph, heated, braked and buffeted by an increasingly thick atmosphere.
"If you are out by several minutes, you could be out by hundreds of kilometers," he said. "The issue is where the station would end up."
Mir's forerunner, the Salyut-7 space base, came back in 1991. It should have landed in the Atlantic. "It ended up striking South America," Crowther said. "The Americans had a similar experience with Skylab. Again, they aimed for the Pacific and ended up going into Western Australia.
"It seems that even though people have very large targets, just because of the complex configurations of these vehicles, it's difficult to predict where they are going to fall along the track."
Mir's orbital pathway could take it as far north as London, as far south as the Falkland Islands. But the worry is where along the ground track the larger pieces will fall.