TODAY | December 22, 2013
>>> let's turn to the daring space walk outside the international space station we watched yesterday to fix a crucial cooling system. the second planned walk will take place on tuesday, this after one of the space walkers accidentally turned on a water switch when he got back in the space station , apparently compromising his suit. as kerry sanders reports for nasa, it's so far so good.
>> reporter: today, a day to shore up the details for the next space walk on christmas eve . two astronauts will again spend several hours tethered to the space station , orbiting earth at 17,000 miles per hour as they try to replace the pump on a malfunctioning cooling system.
>> good news from both crew members. everything is still dry.
>> reporter: a problematic suit almost drown an italian astronaut last july. now there are absorbant bad inside the helmet, even a type of snorkel in the event a suit fills with water again.
>> flying in space has everything to do with the unknown and doing things people have never done before. so you expect things to go wrong. you expect to be surprised. so what you do is you plan extremely carefully.
>> reporter: on saturday the space walk went better than anyone expect sgld i don't know if you guys believe in miracles, but i got the hitch pin on the first try.
>> that's awesome rick.
>> reporter: the astronauts are working urgently to repair the pump because as things currently stand tlrks's only one working cooling pump and the space station has turned off many non-essential systems. on tuesday if all goes well, it will slip into position. it's 7200 pounds, maneuvering it into place will take patience.
>> we'll do a challenge and response and go through slowly and methodically through the timeline.
>> reporter: depending on how things go christmas eve , the astronauts may again be floating back out into the blackness of space on christmas day . for "today," kerry sanders , nbc news, miami.