Jul 15, 2008, 17:26 GMT
Moscow - Two Russian cosmonauts floated out of the International Space Station (ISS) Tuesday in their second spacewalk in less than a week to install a docking target and retrieve an earlier experiment.
ISS Commander Sergei Volkov and Flight Engineer Oleg Kononenko exited the hatch at 1708 GMT. The spacewalk is expected to last five- and-a-half hours.
In their spacewalk debut last Thursday, the cosmonauts successfully retrieved an explosive bolt from the Soyuz space capsule docked in orbit.
The bolt is to be examined later on Earth, in hopes of revealing why the Soyuz spacecraft have been so badly off-course on their last two jolting flights back from orbit.
The main objective of Tuesday's spacewalk is to set up a new seismological experiment - dubbed Vsplesk or Burst - on the exterior of the station, which would act as an early warning system for large earthquakes.
They will also retrieve tubes of bacteria, fungi and larvae left 18 months back, as part of the Biorisk experiment, to study the effects of space on micro-organisms.
The two cosmonauts will mount a docking target for a new laboratory that Russia plans to send up in 2009. The ISS addition will be used for future experiments and expand the crew's living space.
US Flight Engineer Greg Chamitoff, the ISS's third crew member, will remain in the Soyuz during the spacewalk as a precaution, in case the airlock cannot be re-pressurized.
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