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.