itself are not in danger and it's a problem they have dealt with before but their work is cut out for them. as some non-critical systems have been powered down. >> any problem in space is a critical problem. i wouldn't say it is expected but planned for. that's why they have spares. that's why they monitor everything. >> reporter: if it is hardware problem, a space walk could be in the plan and u.s. astronauts would have the best training to make the repair but the first space walk since nasa commanders aborted one this past summer. an italian astronaut could have drowned during routine maintenance when water got in his helmet. engineers are yet to determine the source of the problem in his suit. we expect to hear from mission management thursday morning. at johnson space center, abc news. >> one of the women at the space center described it like a car's radiator that keeps the car cool. when the radiator is clogged and the engine overheats it is almost the same principle.