14 DAY TRIAL // Earlier today, two STS-131 mission specialists stepped out of the International Space Station's (ISS) Quest airlock, to conduct the third and final spacewalk in their schedule. NASA astronauts Rick Mastracchio and Clayton Anderson each performed the sixth extra-vehicular activity (EVA) of their careers, and they managed to successfully complete all the major chores allotted to them. They successfully replaced a large, old ammonia tank on the outer hull of the ISS with a new one and then deposited the old one back into the payload bay of space shuttle Discovery.
Their sortie began at 2:14 am (0614 GMT) and was originally programmed to last for about six and a half hours. However, the two hit an obstacle in their efforts when Mission Control announced them that one of the valves on the four hoses they had just installed appeared to be stuck. The hoses transport liquid ammonia coolant to the tank and are essential for maintaining proper temperature levels on the ISS. As experts on the ground struggled to fix the glitch on their end, Mastracchio and Anderson had their own problems with installing the old ammonia tank in the orbiter's payload.
A stubborn bolt gave them some trouble, which was nothing new. In the previous two STS-131 EVA, the astronauts encountered other instances in which bolts would not budge. They needed to use prybars and even brute force at times to get them loose. This instance was different in the sense that the small metal piece was misaligned. Therefore, the two astronauts needed to unscrew another bolt, align the entire plate properly, and then affix them all back into place. After they completed this chore, they removed some unneeded aluminum coverings from the outer hull of the orbital facility. This task was originally planned for their second EVA, but delays made them leave this job for today.
“We have two roll-over tasks that were originally planned as part of [the second spacewalk] that are going to be added to the front end. After they do that, they'll go on and essentially proceed with the remainder of [the third spacewalk], in large part what was planned pre-flight,” explained Mike Sarafin, the Lead Shuttle Flight Director at NASA. As the astronauts were working outside, their colleagues inside the ISS continued the task of unloading some of the 17,000 pounds (7,711 kilograms) of supplies from the newly-arrived MPLM (Multi-Purpose Logistics Module) Leonardo. Completely unloading the container will take a few more days, NASA officials announce, quoted by Space.