Third ISS EVA Takes Place Today

NASA officials have finally agreed to allow two Expedition 24 flight engineers to go outside the International Space Station (ISS) today, in order to conduct a new spacewalk.

The extravehicular activity (EVA) will be conducted by astronauts Doug Wheelock and Tracy Caldwell Dyson, who will attempt to replace a broken ammonia pump on the outside of the orbital facility.

The pump broke down on July 31, when the Loop A segment of the ISS' cooling system failed. The glitch meant that the labs and modules which were served by the Loop could no longer have their excess heat removed.

This prompted the six astronauts who make up the Expedition 24 crew to power down some systems, in order to prevent them from overheating.

Ever since the situation began unfolding, NASA officials have been adamant that the lives of the six astronauts were never in any danger.

Initially, after the first estimates of the situation were completed, engineers and mission planners said that two spacewalks would be enough to repair the glitch, but it would now appear that the number has doubled.

The first EVA was stifled by an ammonia leak, which saw the two astronauts struggling to contain the dangerous liquid.

During the second spacewalk, the team managed to remove the troublesome pump, setting the site of their intervention up for the third EVA, which is to take place today, August 16.

Today's “trip” will see Wheelock and Caldwell Dyson trying to install one of the four ammonia pump they have in storage aboard the ISS on its position in the main truss rod.

“To prepare for the spacewalk, Wheelock and Caldwell Dyson will spend the night Sunday in the Quest airlock, beginning their 'campout' to start purging nitrogen from their bloodstreams in advance of exiting Quest Monday morning for the planned 6 ½ hour excursion,” NASA says in a press release.

“The failed pump will, for the time being, remain grappled to a payload attachment bracket on the starboard truss,” the document reads.

“No decision has been made as to whether a fourth spacewalk will be conducted by Wheelock and Caldwell Dyson to move it back to the external spare platform or defer that activity to a future spacewalk by a different crew,” it concludes.