An American astronaut and Russian cosmonaut will climb into bulky spacesuits on Wednesday for a rare internal spacewalk at the International Space Station, one that will never venture outside the orbital outpost.
Station commander Gennady Padalka of Russia and NASA astronaut Michael Barratt will take their second spacewalk in less than a week tomorrow when they replace an old station door with a docking cone inside the outpost's Russian segment.
"It's all done internally," said David Korth, spacewalk flight director for the station's six-man Expedition 20 crew. The spacewalkers should finish the work swiftly in about an hour, he added.
The internal spacewalk is slated to begin at about 2:45 a.m. EDT (0645 GMT). Padalka and Barratt will wear their new Orlan MK spacesuits while working in a vacuum inside a spherical, multi-hatch compartment at the forward end of the station's Russian-built Zvezda service module. They will remain connected to the station's interior via spacesuit umbilical lines and tethers.
Only one other time in the 124 spacewalks performed so far to build the station over the last 10 years have spaceflyers performed a similar internal spacewalk, though cosmonauts did stage three spacewalks inside the former Russian Space Station Mir to inspect and repair a damaged module in 1997, NASA officials said.
The last time an internal spacewalk was performed on the International Space Station was in 2001. During that spacewalk, two spaceflyers primed the station to receive its Earth-facing Russian Pirs docking compartment.
On Wednesday, Padalka and Barratt will replace a flat roof-mounted hatch inside the Zvezda module's transfer compartment with a docking cone. The cone, which has been used twice before by Zvezda to dock with Pirs and the Russian Zarya control module, will allow a new room — the Mini-Research Module 2 — to latch onto the space station in November.
The Mini-Research Module 2 is a cylindrical room that will dock to Zvezda's rooftop berth to double as a new airlock and docking port for the space station. It will launch atop an unmanned Russian rocket. Another Russian-built room, the Mini-Research Module 1, will be ferried to the station next year aboard a NASA space shuttle.
Wednesday's spacewalk will be the second this month by Padalka and Barratt to prepare for the new module's arrival. The two spacewalkers ventured outside the space station on June 5 to install a pair of antennas that will help the module dock at the outpost.
The station is currently home to six spaceflyers: two Russian cosmonauts, and one astronaut each from the United States, Japan, Belgium and Canada.
SPACE.com will provide live coverage of tomorrow's spacewalk by Senior Editor Tariq Malik in New York. Click here for live spacewalk coverage, mission updates and SPACE.com's live NASA TV video feed. Friday's spacewalk coverage will begin at 2:15 a.m. EDT.