Cosmonauts Sergei Volkov, the International Space Station commander, and Oleg Kononenko, flight engineer, ventured outside the space station to remove an explosive bolt from their docked Soyuz space vehicle.

The pyrotechnic bolt will be examined back on Earth, as experts in Moscow attempt to figure out why two Soyuz landings have been marred with ballistic descents and partial separations of components on the spacecraft.

In one rough Soyuz landing, a South Korean and a Russian suffered back injuries.

Volkov and Kononenko were spacewalking for 6 hours, 18 minutes, inspecting their docked Soyuz and retrieving the bolt.

Meanwhile, a U.S. astronaut, flight engineer Greg Chamitoff occupied the Soyuz vehicle as a precaution in the unlikely event the spacewalkers would have to enter if the Pirs airlock failed to repressurize.

Tomorrow, Volkov and Kononenko will go spacewalking again, a shorter 5.5 hour stroll in the void. They will remove and install science experiments, as well as install rendezvous equipment for an upcoming Russian mission. That mission, scheduled for next summer, will see an automated docking of a Russian airlock compartment module.