Video: Expedition 50 spacewalk highlights

Two Russian cosmonauts used the International Space Station’s Poisk docking compartment as an airlock for the first time Wednesday in a six-hour 48-minute spacewalk to begin preparing the nearly identical Pirs module for removal next year. A new laboratory module will be parked in its place later.

After prepping their patient — a $2 billion cosmic ray detector — during two earlier spacewalks, two space station astronauts ventured back outside for a third outing Monday to carry out what amounted to transplant surgery, installing replacement coolant pumps in a bid to revive the costly instrument and extend its life.

The next launch of a Soyuz spacecraft carrying three space station fliers has been delayed indefinitely after testing at the Baikonur Cosmodrome in Kazakhstan revealed an unspecified technical problem, the Russian space agency announced Saturday.