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<\/p>\nNASA astronauts Christina Koch and Dr. Jessica Meir exited the International Space Station to begin an Extravehicular Activity \u2013 EVA, or spacewalk \u2013 on Friday that largely saw the duo replace a failed Battery Charge\/Discharge Unit on the Station\u2019s P6 truss structure. <\/p>\n
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. The replacement work was successful.\n<\/p>\n
Unit failure:<\/b><\/p>\n
Overall, the International Space Station has 24 Battery Charge\/Discharge Units (BCDUs) along its Integrated Truss Structure \u2013 the part of the Station that houses the solar arrays and all of the batteries and electrical distribution systems for the outpost.<\/p>\n
BCDUs control the amount of charge put into each battery on the Station\u2019s 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.<\/p>\n
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.<\/p>\n
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The two post-battery swap configurations: without an old nickel hydrogen battery on an Adaptor Plate and with an old nickel hydrogen battery on an Adaptor Plate. (Credit: NASA)<\/p>\n
Last Friday, all three were commanded to reactivate as their associated batteries had completed their replacement sequence.<\/p>\n
Two of the BCDUs reactivated without issue, but a third failed to do so. <\/p>\n
According to NASA, \u201cOn Friday, October 11th, after the completion of US EVA 57 P6 Battery EVA #2, the BCDU 2B2 converter did not close when commanded. The Li-ion battery connected to BCDU 2B2 was safed and still shows good health & status. <\/p>\n
\u201cThe other two BCDUs, 2B1 & 2B3, were successfully activated and are healthy and nominal. BCDU 2B2 troubleshooting was completed \u2026 to power cycle the BCDU and the converter; however, it was not recovered.\u201d<\/p>\n
This resulted in only two-thirds of the potential power from this particular BCDU\/battery channel being available for the Station.<\/p>\n
When the failure occurred, NASA decided to stop the current battery replacement spacewalks and change the next EVA in the sequence to a removal and replacement operation for the failed BCDU.<\/p>\n
While a single failed BCDU might not seem like a critical issue, it follows on the heels of a similar failure earlier this year when a BCDU on a channel of newly replaced batteries failed as well.<\/p>\n