NASA astronauts Christina Koch and Dr. Jessica Meir have exited the International Space Station to begin an Extravehicular Activity – EVA, or spacewalk – that will largely see the duo replace a failed Battery Charge/Discharge Unit on the Station’s P6 truss structure.
The unit failed to reactivate after the first two of a five spacewalk sequence to replace 12 old batteries with six new and improved Lithium-ion batteries.
Overall, the International Space Station has 24 Battery Charge/Discharge Units (BCDUs) along its Integrated Truss Structure – the part of the Station that houses the solar arrays and all of the batteries and electrical distribution systems for the outpost.
BCDUs control the amount of charge put into each battery on the Station’s truss during the 16 sunlight orbital passes each day as well as the amount of power taken off the batteries during the 16 orbital night passes each day.
In preparation for the first two EVAs earlier this month to begin the battery replacement sequence on the P6 truss, three BCDUs on the same power channel as the first batteries to be replaced were turned off.
The two post-battery swap configurations: without an old nickel hydrogen battery on ...