NASA astronauts Robert Behnken and Douglas Hurley launched to the International Space Station (ISS) aboard SpaceX’s Crew Dragon spacecraft on May 30th. They joined Astronaut Chris Cassidy at the ISS laboratory and are now conducting scientific experiments as part of Expedition 63. Before returning aboard the Dragon capsule, the astronauts are assigned to work alongside Cassidy. They are tasked with completing two spacewalks to upgrade the space station’s old battery system. The first spacewalk took place today, Friday, June 25. The second spacewalk is scheduled for July 1st.
Today, at around 7:25 a.m. EDT, astronauts Cassidy and Behnken prepared for their Extravehicular Activity (EVA) mission, also known as a spacewalk. Astronaut Hurley helped them suit up and assisted with controlling the ISS’s robotic arm during the mission. They set their spacesuits to internal power at around 7:35 a.m. EDT. to exit the space station’s hatch and begin their spacewalk towards the battery replacement unit. “Cassidy is extravehicular crew member 1 (EV 1), wearing the spacesuit with red stripes, and using helmet camera #18. Behnken is extravehicular crew member 2 (EV 2), wearing the spacesuit with no stripes and helmet camera #20. It is the seventh spacewalk for both astronauts,” NASA shared.
Astronauts wear a small set of mirrors on their wrist bands during spacewalks to view hard-to-see areas. The mirror is just 5 inches by 3 inches. Today, Cassidy’s mirror on his left wrist unattached and floated away in zero gravity, as he exited the station’s door hatch into space. It floated away at around one foot per second. NASA TV commentator said during the live-broadcast that it posed no danger to the astronauts, nor affected the mission tasks; Cassidy still had a mirror on his right wrist to utilize.
During the spacewalk, they were tasked with switching the space station’s batteries. The brave pair changed the old nickel-hydrogen batteries with new lithium-ion batteries on a structure called ‘Starboard-6’. These batteries are used to store solar energy from the station’s solar arrays. ISS orbits Earth very fast at approximately 4.76 miles per second; It completes a full orbit around the entire planet every 90 minutes – which means the space station remains in daylight for 45 minutes and darkness for 45 minutes, so, every 24 hours the space station remains in darkness 16 times per orbit. The batteries store energy to power the laboratory when there is no sunlight during orbital night periods. “We are going with newer technology with the lithium-ion battery. Basically, a newer technology with a smaller footprint. You can get way more [energy] storage capacity on orbit, which is the reason that we made the leap of technology several years ago. […] For the past four years now, over four years, we have been slowly swapping out from the nickel-hydrogen to the lithium-ion,” ISS Deputy Program Manager Kenny Todd explained.
Behnken and Cassidy’s spacewalk lasted 6-hours, it was completed at around 1:39 p.m. EDT. They successfully swapped the battery unit on a structure called ‘Starboard-6.’ For hours, the astronauts carefully spacewalked back and forth between the truss and the battery area. To install the new batteries into place, and store the older batteries inside a metal box for disposal. Cassidy and Behnken would verbally tell each other their actions “I’m in control of the battery,” one would say to ensure they let each other know who has a grip of the object, “You’re in control,” the other would respond.
Five out of six old nickel-hydrogen batteries for one of two power channels in the Starboard-6 truss were removed. The astronauts then installed two of three new lithium-ion batteries along with two adapter plates that are part of the power circuit to the lithium batteries. NASA Mission Control reports that the two newly installed batteries are working. The battery replacement spacewalk was successfully completed 2-hours ahead of schedule.
During the second spacewalk scheduled for Wednesday, July 1st, Cassidy and Behnken will remove the sixth nickel-hydrogen battery and replace it with a lithium-ion battery and add one more adapter plate.
NASA said – “This was the seventh spacewalk for both astronauts. Cassidy now has spent a total of 37 hours and 21 minutes spacewalking, and Behnken has spent a total of 43 hours and 40 minutes spacewalking.”