Astronauts will use robotics in at least one of two emergency spacewalks that have been set up to make critical repairs to the International Space Station after part of its cooling system stopped working over the weekend. To get the ailing space station back up and running, an astronaut will ride a robotic arm 210 miles above the Earth and while moving at 17,500 miles an hour.
A failed ammonia pump on the orbiting station triggered alarms Saturday evening, waking the six astronauts on board. Astronauts immediately began shutting down several systems that aren't needed for life support to lessen the strain on the station's one remaining working coolant system. According to NASA, two gyroscopes were shut down, along with power converters and communication and GPS back-up systems.
NASA reported that engineers working from Ground Control tried to remotely restart the ammonia pump on Sunday but could not get it working again.
Rob Navias, a NASA spokesman at the Johnson Space Center, said today that the agency expects astronauts Doug Wheelock and Tracy Caldwell Dyson, who have been living on the station, to conduct two emergency spacewalks. The first spacewalk is expected on Thursday; the second will likely take place on Sunday or next Monday.
There are two spare pumps already onboard the space station. The pumps push extremely cold liquid ammonia through the station to get rid of excess heat from the orbiter's systems and laboratories. They're critical to keeping the orbiter from overheating, which would affect the people onboard, as well as the technology supporting the astronauts and their scientific work.
The spacewalkers will need to detached the failed ammonia pump from the outside of the space station and then replace it with a new pump.
According to Navias, the astronauts will rely on the station's primary robotic arm, dubbed Canadarm II, for much of the work scheduled for Thursday. One astronaut will be secured in a foot restraint on the end of the robotic arm while he removes the failed ammonia tank from the station.
"Instead of being tethered and free floating, this provides leverage for the crew member," said Navias. "With their feet planted they're able to move the mass of this object around with less difficulty... It'll save us a lot of time."
Canadarm II is frequently used during spacewalks at the station. In April, the robotic arm was used to lift a replacement ammonia tank out of space shuttle Discovery and move it into place on the outside of the station.
Canadarm also was used in February when it helped to move and attach a seven window cupola was attached to the space station. The cupola, which now serves as a central command post for the station's robotics work, also has the added bonus of providing the space station crew with a stellar view.