{"id":37526,"date":"2020-07-02T01:10:17","date_gmt":"2020-07-01T17:10:17","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/astronauts-complete-second-spacewalk-of-iss-battery-replacement-efforts\/"},"modified":"2020-07-02T01:10:17","modified_gmt":"2020-07-01T17:10:17","slug":"astronauts-complete-second-spacewalk-of-iss-battery-replacement-efforts","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/astronauts-complete-second-spacewalk-of-iss-battery-replacement-efforts\/","title":{"rendered":"Astronauts complete second spacewalk of ISS battery replacement efforts"},"content":{"rendered":"

Chris Cassidy and Bob Behnken have completed the second in a series of four spacewalks, or EVAs, that will complete replacement of the last set of Station batteries, which were delivered to the outpost in May on the Japan HTV-9 cargo vehicle.<\/p>\n

Three years ago, NASA began the effort to replace all of the Station\u2019s Nickel-Hydrogen batteries originally launched with the solar arrays.  Today was the 66th U.S. Station spacewalk in support of the orbital laboratory.<\/p>\n

EVA background:<\/p>\n

The ISS features expansive solar arrays that use sunlight to power the station\u2019s many systems. However, since the ISS spends about half of every orbit in darkness, it also needs batteries to store that solar energy, which can then be used to power the ISS during periods of orbital darkness.<\/p>\n

There are eight independent \u201cpower channels\u201d on the ISS in total (two channels per each of the four solar array Truss segments), with each channel having its own set of solar arrays and batteries.<\/p>\n

Originally, each power channel had six Nickel-Hydrogen (Ni-H2) batteries; however, since these batteries had a lifetime of 6.5 years each (although ultimately they performed for much longer than that), it was always known that they would have to be replaced at some point during the station\u2019s lifetime.
\n\"\"The first Truss element launched to the ISS \u2013 the P6 Truss in December 2000 \u2013 which was used to provide power to the ISS during the early years of its construction, had its batteries replaced with new Ni-H2 batteries throughout 2009 and 2010.<\/p>\n

However, with the remaining solar array Truss segments having been launched in 2006 (P3\/P4), 2007 (S3\/S4) and 2009 (S6), in 2017 an effort to replace all the station\u2019s batteries was initiated.<\/p>\n

The original Ni-H2 batteries had at this point been superseded in battery technology by Lithium-Ion (Li-Ion) batteries, which are lighter and have a much higher power density than Ni-H2 types.<\/p>\n

This proved advantageous for the ISS program, as it meant that one Li-Ion battery could store as much power as two Ni-H2 batteries, which therefore halved the number of batteries that would be needed for the replacement effort.<\/p>\n

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However, since the original Ni-H2 batteries were connected in pairs called a \u201cstring\u201d, Adapter Plates were also needed to enable one new Li-Ion battery to connect to two slots that were previously occupied by Ni-H2 batteries.<\/p>\n

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Adaptor Plate and Battery \u2013 via NASA<\/p>\n

The Japanese HTV-6 cargo craft in December 2016, HTV-7 in September 2018, and HTV-8 in September 2019 each brought six new Li-Ion batteries and Adapter Plates to the station, which were used to replace the Ni-H2 batteries on the P3\/P4, S3\/S4, and P6 Truss segments.<\/p>\n

The batteries on the P3\/P4 and S3\/S4 segments were able to be replaced robotically via the Special Purpose Dextrous Manipulator (SPDM) \u201cDextre\u201d. However, the batteries on the P6 Truss required spacewalks to replace them, as the P6 Truss is located on the very outboard end of the ISS and is out of reach of the station\u2019s robotic arm.<\/p>\n

Most recently, the HTV-9 cargo craft in May 2020 launched the final set of Li-Ion batteries to replace the Ni-H2\u2019s on the S6 Truss segment \u2013 which is being done last as it is the most recent truss segment to launch to the ISS (March 2009).<\/p>\n

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The new ISS batteries ahead of being launched on the HTV \u2013 via JAXA<\/p>\n

As with the P6 Truss, the S6 Truss batteries will also require spacewalks as the worksite is beyond the reach of robotic assets.<\/p>\n

Since there are two power channels located on the S6 Truss, a total of six Li-Ion batteries and six corresponding Adapter Plates (AP) will be required to replace the twelve Ni-H2 batteries on the segment.<\/p>\n

The six new Li-Ions and APs, which are attached to HTV-9\u2019s Exposed Pallet (EP), have been robotically pre-positioned near the S6 Truss worksite in preparation for the spacewalk.<\/p>\n

EVA sequence:<\/p>\n

The first spacewalk occurred on 26 June and was known as U.S. EVA-65. After exiting the Quest airlock, EV-1 Chris Cassidy and EV-2 Bob Behnken translated out to the worksite at the S6 Truss \u2013 specifically the 1B Integrated Electronics Assembly (IEA). They began the task of replacing channel 1B\u2019s Ni-H2 batteries with the new Li-Ions.<\/p>\n

The duo first removed one of the old Ni-H2\u2019s and installed it into an empty slot on the HTV\u2019s EP. They then removed a new Li-Ion from the EP and installed it into the now empty slot on the S6 IEA.<\/p>\n<\/p>\n