The second spacewalk of space shuttle Discovery鈥檚 13-day mission began on Monday with astronauts Piers Sellers and Mike Fossum lifting a huge pump with their gloved hands. On Earth the pump would weigh 635 kilograms (1400 pounds).
鈥淚t鈥檚 very, very easy to hold it steady,鈥� Sellers said. 鈥淚鈥檓 very relaxed.鈥� The pump needed to be moved so that the space station鈥檚 Canadian-built robotic arm could take hold of it. The pump is a spare part for the station鈥檚 heating system and is being stored on a spare parts platform on the station for use at a later date.
The spacewalk began at 0814 EDT (1214 GMT) on Monday and is scheduled to last 6.5 hours.
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Among the astronauts鈥� other tasks will be to replace a system that sends power and commands to a railcar attached to the station鈥檚 truss. The truss acts like a backbone to the station and supports its power-generating solar arrays.
The station鈥檚 robot arm moves on the railcar to access hard-to-reach areas. The railcar is critical for future missions to install more solar arrays and truss segments.
Blade-blocker
In December 2005, a cable was inadvertently cut on one of two systems that power and send commands to the railcar. The device can operate with just one system, but NASA prefers to move it only when both systems are working.
On the mission鈥檚 first spacewalk on Saturday, Sellers and Fossum installed a 鈥渂lade-blocker鈥� to ensure that the other system鈥檚 cable cannot be inadvertently cut.
At one point during Monday鈥檚 spacewalk, Sellers will take the broken railcar system in one hand while holding its replacement in the other 鈥� each would weigh 150 kilograms (330 pounds) on Earth.
The pair has one more spacewalk after this, which will aim to test repair equipment for the shuttle鈥檚 heat shield.
Keep up-to-date on the mission by visiting our .
