Astronaut Piers Sellers has six spacewalks to his credit, including a test run riding the end of the shuttle's robotic arm last summer to check out techniques for repairing damage to the ship's heat-shield tiles. He is working on the team at the Johnson Space Center to plan a spacewalk to repair the damage to the Shuttle Endeavour if it's necessary. He discussed the complexities of planning such a spacewalk with ABC News Correspondent Mike von Fremd.
ABC News: You are one of the only people who have experience riding the arm under a shuttle. How bulky is the equipment you are wearing, and how precarious is it to ride the arm?
Piers Sellers: There are a number of things that factor into this. The first thing is that the shuttle arm that is about 50 feet, would grab this long stick, or boom, which is another 50 feet, and on the end of that you've got a couple of astronauts and all their tools, and then you lift them out of the payload bay and then very carefully extend the whole thing out underneath the shuttle and bring them up to the repair site. That is a complicated effort because you have to move the arm very carefully. You have these two big guys standing on the end of a long skinny 100-foot pole, then you bring them up to the site and they carefully get out their tools and fix the hole.
ABC News: When you say standing on a pole – you are weightless, but do you still have balance issues?
Sellers: You are weightless but you have a little platform that is attached to the end of the pole with a couple of foot loops you can put your toes through, and so you are standing on this little platform the size of a phone book, quite secure and quite relaxed, standing upright on the end of a pole. It looks comical, if you have seen the photo it looks like two fat guys on the end of a telephone pole.
ABC News: How difficult is it to do skilled handiwork when you are in that kind of precarious position?
Sellers: It is a little bit like you are standing on a boat, a small rowing boat, trying to repair something on a dock, or a big boat, there is some movement, you are aware of some slight movement, if you are careful, and you take your time -- it is not too difficult.
ABC News: What is the potential for further damage to the space shuttle on a spacewalk?
Sellers: This is a long flexible object and you have to move very slowly when you are close to delicate surfaces of the shuttle, to make sure you don't overshoot and whack into the tiles and do more damage. So it is a question of going very slowly and very carefully and creeping up on the problem.
ABC News: Are you in constant contact with the robotic arm operator? How do they know where you are and what you are doing?
Sellers: We did a test of that last summer, we managed to get it to go within a couple of inches of where you needed it to be; it takes a little time, but it is quite safe.
ABC News: You are talking about outer space in a bulky spacesuit. This sounds very difficult.
Sellers: Working in the suit is something we have all trained to do, the crew that is up there right now has trained literally for years in a spacesuit and it is like a second skin, a big lumpy second skin, they know how to operate it, the same with all the tools, and with the communications you have access to the brain trust down in Houston, from every point of view there are a lot of problems, there are a lot of difficulties, but each one of them has some expertise to help you out and get the job done.
ABC News: But there is the potential for something bad to happen?
Sellers: That is why you have to be careful, that is why NASA is not jumping into this lightly, why they are doing a lot of analysis to make sure this is the safest thing to do.
ABC: What makes this so daunting?
Sellers: The things you are trying to avoid are making the problem worse by breaking more tiles, impact with a tool, and that is why people are spending a lot of time and effort, analyzing this to find the safest approach to do the work.
ABC News: If you were up there would you be ready to do this?
Sellers: That is an unfair question for a spacewalker because we always like to go outdoors, so the decision will be made by the mission management team down here, the crew is always ready to do anything or not do anything.
ABC News: What are the risk-reward benefits of doing this on orbit?
Sellers: If we could bring the shuttle back right now with no damage at all, that would be the best thing. If we could do a repair and bring it back with no serious damage that would be even better, but if we were to bring it back and there was some damage to the skin, that could put us back a few weeks and many millions of dollars to fix it on the ground. That factors into the equation.
ABC News: Are you discouraged by how often foam is a problem?
Sellers: It is going to be a problem, and we are going to have to watch this one like a hawk through the rest of the shuttle program -- we really are -- that is the nature of the beast.
ABC News: NASA has done a lot to mitigate the problem, will you ever solve it?
Sellers: We have done a lot to mitigate the problem and I think the biggest thing we have done is a complete toenails to ears inspection of the shuttle every time it goes into orbit before we come home. That is critical. We know what damage has been caused, and we have got lots of options if we find damage, so I think we have done a lot to mitigate the problem.
ABC News: Will you be watching the shuttle landing with a lump in your throat?
Sellers: I am taking them at their word that this is not a life threatening event, and I hope it is not even an orbiter singeing event. I hope whatever we decide, whether we repair or don't repair, we cause minimum damage to the shuttle. As far as the crew is concerned, I think they are going to be completely safe.