Astronauts Complete Shortened Spacewalk to Replace Faulty Power Unit

Two astronauts aboard the International Space Station have completed an abbreviated four hour, forty three minute-long spacewalk to replace a faulty power unit on the exterior of the International Space Station.

On their 32nd day in space, NASA astronaut Tim Kopra and Tim Peake of the European Space Agency began their Extra-Vehicular Activity(EVA) from the U.S. Quest airlock at 12:48 p.m. GMT. while the ISS was flying 250 miles over the Southern Indian Ocean.

Tim Peake smiles for the camera as he became Britain's first astronaut
to walk in space. credit: NASA

They quickly translated some 200 feet to the S6 truss on the starboard edge of the space station to remove a faulty power regulator known as a Sequential Shunt Unit(SSU) that failed on November 13 2015.

Working in tandem, the pair removed the old Sequential Shunt Unit while the station was in orbital night time. This removed the possibility of sparking as no power was being generated by the station's solar arrays at this time. Kopra and Peake installed a new SSU a short while later. The new unit is nicknamed "Dusty" as it has been aboard the complex since 1999.

Aboard the International Space Station are eight power channels along which solar power generated by the station's eight solar arrays flows to operate on board systems. The purpose of the SSU is to regulate power output of the solar arrays to 160 volts. The ISS can operate with only seven channels in operation, but if another were to fail some on board systems would need to be shut down.

With the primary task of the Extra-Vehicular Activity(EVA) complete, the spacewalking duo focused their attention on routing a series of cables that will be used to prepare the orbiting laboratory for the upcoming installation of International Docking Adapters on Pressurised Mating Adapters that will serve as docking ports for future commercial crew and resupply vehicles visiting the International Space Station.

However shortly after 4 p.m. lead spacewalker Kopra soon noticed that a volume of cold water had found its way into his helmet. He also noted that his shoulders and wrists were also wet as a result of the leak.

The drinking water astronauts use to keep hydrated is kept at ambient temperature, indicating that the water stemmed from a leaking cooling garment inside his spacesuit.

Although the spacewalkers were in no immediate danger, lead Flight Director Royce Renfrew made the decision to terminate the EVA early and bring Kopra and Peake back inside.
Renfrew later spoke to NASA Public Affairs Officer Rob Navias on his decision which you can watch here.

"We're in a terminate case," radioed NASA astronaut Reid Wiseman in Mission Control, relaying Renfrew's decision. "We want you to start heading back to the airlock."

This follows a similar incident in July 2013 in which ESA astronaut Luca Parmitano's helmet filled with a large volume of water, leading to the immediate abort of that particular spacewalk.

This was the 192nd spacewalk in support of space station assembly and maintenance. Today also marks the first time a British citizen has conducted an EVA with Tim Peake making the first spacewalk of his career. Today's excursion marks the third spacewalk for Tim Kopra.