Astronauts reflect on critical repairs to space station (Q&A)

The International Space Station's coolant system is back up and running normally after a challenging three-spacewalk repair job, astronauts said Thursday.

The fix allows the crew to power up science equipment and other systems that had to be shut down when an ammonia pump shorted out July 31.

In an interview with CBS News, the station's three NASA astronauts--robot arm operator Shannon Walker and spacewalkers Douglas Wheelock and Tracy Caldwell Dyson--said the impromptu repair went well, despite unexpected problems.

"I think it was really NASA at its finest with all the teams on the ground and the folks up here working together to get this repair done in short order," Walker said.

The pump failure shut down one of the space station's two coolant loops, forcing the crew to implement a widespread powerdown to prevent equipment from overheating. Two spacewalks were quickly planned, one to remove the old pump and install a spare and another to reconnect four ammonia lines.

But Wheelock and Caldwell Dyson, faced with an unexpected leak, were unable to disconnect one of the coolant lines attached to the failed pump and the first spacewalk ended August 7 with the original pump module still in place.

Flight controllers then lowered pressure in the line to stop the leak and during a second spacewalk on August 11, Wheelock and Caldwell Dyson finally got the balky M3 connector to release. The old pump was removed and the replacement was installed during a third spacewalk on Monday.

The astronauts and flight controllers at the Johnson Space Center in Houston then re-activated coolant loop A and restored the station to normal operation.

Walker, Caldwell Dyson, and Wheelock discussed the repair work with CBS News space analyst William Harwood in a space-to-ground interview Thursday. Here is a transcript of the conversation (questions edited for length):

CBS News: Can you give us an update on coolant loop A and where things stand this morning?
Caldwell Dyson: Well, as far as we can tell, everything's coming back up...We've got most of our lab back and our node 2 back, both JEM (Japanese Experiment Module) and Columbus are all back, so to us here on orbit things are looking better than normal.

CBS News: So all the black boxes, all the power converters, all the lab racks are back up and running?
Caldwell Dyson: Yeah, Shannon and Doug removed the last jumpers today and put the racks back so it's all spic and span and it's back to business as usual it seems.

CBS News: This coolant loop problem, you can really look at it two ways. You can say problems like this demonstrate how difficult it's going to be to maintain station after the shuttle's retired and you can't bring big components back to Earth to be repaired. But you demonstrated a pretty impressive ability to respond in real time and deal with a pretty difficult challenge. How do you look at at?
Walker: I think you're right on both accounts. It will be more difficult for the engineers who are designing the hardware and want to understand the failure modes of the hardware that we see up here since we won't be able to bring things back, such as large ORUs (orbital replacement units) and large pumps. But it also demonstrates how we can respond in an emergency. I think it was really NASA at its finest with all the teams on the ground and the folks up here working together to get this repair done in short order.

CBS News: I assume, then, that you're confident down the road that when things like this happen you guys are going to be up for that?
Wheelock: Yeah, I'd have to agree with Shannon that the confidence is real high now. It was a validation, really, of our teamwork, our training, everyone involved. The way everything came together, it was just a great lesson in teamwork and how to stick to it and really solve a problem. I think the confidence is real high now in the team as we press forward.

CBS News: Doug, they told us you and Tracy practiced a pump changeout back in 2009. Compared to shuttle-type training, where it's all very specific and very detailed, you get more generic training on the station. How did that work out? How tough was it to get back up to speed on techniques and procedures for something like this?
Wheelock: Our training in the NBL (Neutral Buoyancy Laboratory) back in Houston, in the pool, a lot of it is skills based ... and those skills came in very handy. But when you get outside with the temperature changes and of course, with the pure vacuum out there, things don't behave sometimes as they do on Earth. So we have to be ready for those things and we're trained to troubleshoot those things and come up with some potential solutions. Some of them are more elegant than others, but we got it done. It was just a real lesson in how to take your skills and a little bit of creative thinking and ingenuity and get the job done.

CBS News: Shannon, how about you, getting up to speed on arm operations for something like this. You played a pretty critical role in all this.
Walker: Yeah, the arm ops were quite interesting because just like with the spacewalk operations, I was trained sort of generically and so I never saw these procedures until right before I needed to do them. In fact, on the second EVA, I did not get the final procedures until the day of (the spacewalk). So I really had to depend on my skills to be able to fly something that I had no prior knowledge of.

CBS News: Let me ask a couple of spacewalk questions. Tracy, these were your first spacewalks and I know it's all work and no play out there, but what were your impressions when you had a moment to look around?
Caldwell Dyson: When I had a moment to look around, it was pretty awe-inspiring. You know, for the last four or five months I've been looking out our cupola window at the sunrises and sunsets and been brought to tears by the multitude of stars once the sun goes down. And I wondered just how I would feel when I went out there. For me, my first EVA was a culmination of 12 years of training and being here and watching and learning and having a huge desire to do that. And so the feeling I was having out there, being on structure, outside the space station, was as emotional as you can get in an EMU (spacesuit), looking out at the sunrise for the first time. It was, like I said, a culmination of so much desire and years of training, it was a feeling I'll never forget.

CBS News: It almost sounds overwhelming. Is it ever difficult to focus on the work at hand?
Caldwell Dyson: I was kind of afraid that it would be, but to be honest when I had those moments where I could look out, it was when either Wheels was doing something and the ground was talking to him and I had a break or it was a moment I stole. It didn't detract at all. It just added to the experience out there. I wish I had better words to describe it.

CBS News:I don't know that anyone else could do any better. Doug, these were your fourth, fifth and sixth spacewalks, you're an old hand at it. That first EVA when fairly smoothly until you got to M3. What were you thinking when you couldn't release that quick-disconnect and then you saw an ammonia leak?
Wheelock: Well, it wasn't a surprise. In fact, when I first started talking to Tracy before we went out I said don't be surprised if things don't go as planned because these 400- to 500-degree temperature changes in 45 minutes, when you're dealing with pieces of metal and rotating parts and things like that that have locking collars, things like that, bales that throw, that things may not be as they seem and not act as we trained in the pool. And sure enough, we saw that.

I think the greatest thing I learned on my earlier EVAs is just to expect that, just take a deep breath, think about the different ways you can finesse the piece of hardware and listen to what your ground trainers are telling you and don't give up trying. We kept at it. M3 became my giant through this whole thing that I had to face out there. We did it together and we needed both of us on either end of the line to find that sweet spot to mate it up and de-mate it as well. I don't know, it sort of became the villain for us. We needed a villain to sort of fight against when we were out there and it became a real challenge for us. But we were able to rise to the challenge as a team.