Three astronauts got an unpleasant taste of what early spacefarers had to cope with this week, when their spacecraft executed a fiery nosedive through Earth鈥檚 atmosphere.
On 19 April, a Russian Soyuz TMA-11 capsule unexpectedly switched to 鈥渂allistic re-entry mode鈥� on its journey home from the International Space Station. It was carrying South Korea鈥檚 first astronaut, Yi So-Yeon, Russia鈥檚 Yuri Malenchenko and NASA鈥檚 Peggy Whitson.
Ballistic re-entry relies solely on atmospheric drag to slow a spacecraft and can expose crew members to gravitational forces 10 times those on Earth. It was standard for the early US Mercury and Soviet Vostok spacecraft, but is a last resort for modern spacecraft. The Soyuz capsule design usually allows for some aerodynamic lift during re-entry, which provides a slower, more shallow descent.
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鈥淥bviously, we鈥檇 rather they had a normal re-entry,鈥� says John Petty of NASA鈥檚 Johnson Space Center in Houston, Texas, but ballistic re-entry is 鈥渟omething that we鈥檙e familiar with and reasonably comfortable with鈥�.
During the capsule鈥檚 descent, mission controllers in Moscow apparently lost track of it for about half an hour. So they were unaware that the capsule had switched re-entry modes and that as a result had touched down 475 kilometres from its expected landing site.
It is not the first time a Soyuz capsule has resorted to this mode of re-entry. It happened in 2003, and again in October last year. Software and hardware glitches were factors in these cases. The cause of this latest mishap is under investigation.
