Transcript for NASA Begins Series of Spacewalks to Fix Space Station Cooling System
We're going to turn to the high drama happening right now at the international space station. A dangerous spacewalk this morning to fix the crucial cooling system. And abc's mike boettcher has the latest on how the risky repair is going from inside the johnson space center in houston. Good morning to you, mike. Reporter: Good morning, bianna. I'm inside the mockup of the international space station at the johnson space center in houston. And this is the airlock module, that astronauts use to train for spacewalks. This is the compartment they will enter the vacuum of space to fix their alien spacecraft. The mission is critical. Fix a failed cooling system that keeps the space station functioning. A repair that nasa says cannot wait, despite concerns about another possible problem. A spacesuit failure. It's like doing a ballet with a washing machine. It's true. We're here -- it has to be really, really graceful. Reporter: Veteran american spacewalker, rick mastracchio will be teamed with hopkins during the operation. Tracy coldwell-dyson repaired the same pump three years ago. You have this really important task. And when you realize that it's just the two of you, out in the vacuum of space, your own breath becomes something very loud inside your helmet. Reporter: Complicating matters is the potential of water selecting in their space helmets. A problem that came close to drowning an italian astronaut during a spacewalk last july. My head is really wet. Reporter: Nasa is not sure what is causing the problem. But in typical nasa fashion, engineers came up with two ingenious fixes. A pad placed inside the helmet. And a 20-inch plastic tube that would allow spacewalkers to breathe air from the bottom of their suits. Spacewalks only look easy. The anticipation of knowing what it feels like to be outside in the vacuum of space, to have something between you and the earth, but your visor. Reporter: At this moment, the astronauts are still in this space lock. When they do walk, it could last up to seven hours. An is the first of possibly three walks to repair their station. Dan? Mike boettcher inside the mockup of the international space station. Thank you.
This transcript has been automatically generated and may not be 100% accurate.