Astronauts Mastravvhio and Hopkins Complete First in Series of Spacewalks

On Sunday, Dec. 22, NASA astronaut Mike Hopkins tweeted this photo of Saturday's spacewalk, saying, "Wow... can't believe that is me yesterday. Wish I could find the words to describe the experience, truly amazing."

Expedition 38 Flight Engineers Rick Mastracchio and Mike Hopkins wrapped up a 5-hour, 28-minute spacewalk outside the International Space Station at 12:29 p.m. EST Saturday. 

They completed the first in a series of excursions aimed at replacing a degraded ammonia pump module associated with one of the station's two external cooling loops that keeps both internal and external equipment cool.

A second spacewalk to install a replacement pump module is scheduled for Tuesday, Dec. 24 at 7:10 a.m. EST, with NASA TV coverage beginning at 6:15 a.m. EST.

Credit: NASA

NASA Shuttle Atlantis: Era’s Final ISS EVA

Spacewalker Ron Garan rides on the International Space Station's robotic arm as he transfers a failed pump module to the cargo bay of space shuttle Atlantis. 

Garan and fellow Expedition 28 astronaut Mike Fossum wrapped up a six-hour, 31-minute spacewalk Tuesday afternoon, performing upgrades and maintenance on the orbiting outpost.

It's the final scheduled spacewalk during a NASA Shuttle mission.

Image Credit: NASA

The Astronauts bounced between the International Space Station and the payload bay of the shuttle Atlantis during a demanding July 12 spacewalk in which they exchanged a failed thermal control system coolant pump from the orbiting science laboratory for a robotic satellite refueling demonstrator.


Though the astronauts got off to a late start at 9:22 a.m. EDT, the two men drew on their experience gained over three station assembly spacewalks in 2008 to recover. Atlantis astronaut Rex Walheim choreographed the 6-hr. 31-min. excursion.

The balky pump’s retrieval was a high priority for the Atlantis crew, who docked at the space station July 10, two days after lifting off on the STS-135 supply mission, NASA’s final shuttle flight.

The device that circulates ammonia coolant through the station’s outstretched starboard radiators failed prematurely on July 31, 2010.

The shutdown prompted a dramatic power down of the station, from which station managers recovered with a series of hastily planned spacewalks over three weeks.

 The source of the pump loss, an internal short circuit, remains unexplained. Once the hardware is back on Earth, it will undergo a failure analysis that could lead to a design change for circulation hardware.

Next, the spacewalkers hauled the boxy refueling demonstrator from the orbiter to Dextre, the two-armed Canadian robot secured to the station’s exterior. The demonstrator, developed by the NASA Goddard Space Flight Center and the Canadian Space Agency, is tentatively scheduled for trials later this year.

In other activities, the spacewalkers activated the Optical Reflector Materials Experiment that was placed on the station’s starboard solar power truss in May. The collection of optical material samples is scheduled to be retrieved next year to evaluate how well they weathered vacuum, solar radiation and the effects of atomic oxygen. Each sample is a candidate for future spacecraft fabrication.

NASA-International Space Station - Coolant Pump Repair EVA

Expedition 24 Flight Engineers Doug Wheelock (left) and Tracy Caldwell Dyson work to remove a failed ammonia pump module on the International Space Station's S1 Truss. Credit: NASA TV

The next spacewalk to complete the removal of a failed ammonia pump module and installation and activation of a new pump module on the International Space Station’s S1 Truss will take place no earlier than Wednesday.

Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson completed the first spacewalk to remove and replace the pump module at 3:22 p.m. EDT Saturday. As the result of an ammonia leak in the final line that needed to be disconnected from the failed pump module, the day’s tasks were only partially completed. The decision was made to reconnect the line on the pump module and install a spool positioning device to maintain proper pressure internal to the ammonia line.

Teams on the ground are evaluating the impact of the leak on plans to replace the failed pump, as well as possible fixes for the leak. The completion of the process will most likely require at least two additional spacewalks.

Saturday’s excursion lasted 8 hours, 3 minutes, making it the longest expedition crew spacewalk in history and the sixth longest in human spaceflight history.

Wheelock conducted the fourth spacewalk of his career. Caldwell Dyson made her first spacewalk. Flight Engineer Shannon Walker operated Canadarm2, the station’s robotic arm, and assisted the spacewalkers from inside the station.

After the loss of one of two cooling loops July 31, ground controllers powered down and readjusted numerous systems to provide maximum redundancy aboard the orbiting laboratory. The International Space Station is in a stable configuration, the crew is safe and engineers continue reviewing data from the failed pump.