Posted on May 28, 2012 by Samantha Cristoforetti
We expect the best, but prepare for the worse
There are also specific risks inherent to a spacewalk and one of the most dreaded scenarios involves a spacewalker going unconscious due to a medical issue or a malfunction of the pressurized suit. Over 150 spacewalks have been performed to assemble the Space Station and such a dramatic scenario has never occurred. However, you will not be surprised to hear that it does materialize quite often during training in the Neutral Buoyancy Laboratory (NBL).
During the EVA training flow future crewmembers are required to demonstrate the ability to rescue an unconscious fellow spacewalker by bringing him or her safely back into the airlock within 30 minutes. I had a chance to try the rescue for the first time last Thursday during a six-hour run in the NBL with veteran spacewalker Steven Swanson (Swanny).This being my first attempt at the rescue, the scenario was extremely simple. I knew in advance that Swanny was going to simulate unconsciousness and I was right next to him on the truss. Also, neither of us was carrying anything at that point, and we were both attached to structure only with our respective safety tethers and one extra tether. We call this latter the local tether, since we attach it locally at a worksit to be able to work with both hands.
Safety tethers, on the other hand, are thin steel cables that are coiled in a reel. We attach one end to structure as soon as we exit the airlock, and since we carry the reel with us, the cable uncoils as we move away and recoils when we come back. If we need to go far out on the truss, we might even have to carry a second safety tether to attach when the first one runs out, and having to make the swap on the way back with an unconscious crewmate would require extra precious time.
But it was not the case for me on my first try. I merely had to detach Swanny’s local tether and use it secure him to myself, and then stow his safety tether, since we would be both secured by mine. Sounds quick and easy, right? Well, I guess it could have been. In reality, when I was ready to move, I realized that I had created a tether tangle and I would have to take the time to fix it if I was going to go anywhere. Good lesson learned!Nothing in the suit is easy, but the rescue seems to be in a category of its own. It’s quite a challenge to manage the bulky suit of the unconscious crewmate by pushing or pulling it on a tether, while at the same time making sure that it doesn’t bump into structure, especially not with the relatively fragile visor. And it’s quite a challenge to manoeuvre him or her into the airlock in an expedient manner, and to enter as second without the colleague helping, or at least getting out of the way. I was sure thankful to Swanny for showing me some veteran’s tricks to do that!
For a scheduling coincidence, I had my first rescue scenario as a robotic operator the very next day. When EVA crewmembers are attached to the Space Station Robotic Manipulator System, or Canadarm 2, they must count on the robotic operator to bring them quickly and safely back to structure in case of an emergency. One more skill I’ll be trying to acquire in the next few weeks, but the details are for another day...