two cooling systems, one goes down, that's okay, we still have another one, but you want to get it back up. bill: can you fix it with a says walk? >> well, they're trying to figure out if that's necessary. right now there's a valve that's involved that is causing some trouble for them. if they have to replace the whole unit, they practice doing that on the ground. you've got two very good space walkers, very experienced astronaut. mike hopkins is a rookie astronaut, but he's a great space walker. i've been in the pool with him, so i think the space station's in good hands. if they have to replace a module, if that's necessary, they can -- bill: what do you mean in the pool? >> that's where we practice our space walks, and we do a lot of training in there to prepare for things like this. will: you can certainly relate to things they're going through right now. are they concerned? >> i think they're definitely concerned about it, and they're trying to work with the ground be, the control team. you've got these really smart people who are working around the clock to try to fix this