Astronauts Christina Koch and Jessica Meir for a five-and-a-half-hour spacewalk — the first ever carried out by two women — to replace a faulty component in the lab's solar power system.
It will be the in the 54 years since the late carried out history's first spacewalk, or EVA (extravehicular activity), in 1965. Cosmonaut Svetlana Savitskaya became the first woman to walk in space during an outing with a male cosmonaut in 1984. NASA astronaut Kathryn Sullivan followed suit later that year, joining astronaut David Leestma for a shuttle spacewalk.
Koch became the 14th woman to walk in space earlier this year and Meir will be the 15th. Other than Savitskaya, all are current or retired NASA astronauts.
Here are a few facts and figures about Friday's excursion and the astronauts taking part.
Christina Koch, 40NASA astronaut Christina Koch aboard the International Space Station. NASA
14th woman to walk in space
Previous spacewalks: 3
03/29/19: 6 hours 45 minutes; solar array battery replacement (left inboard array); with Nick Hague10/06/19: 7 hours 1 minute; solar array battery replacement (right outboard array); with Drew Morgan10/11/19: 6hours 45 minutes; solar array battery replacement (right outboard array); with Drew Morgan
Spacewalk call sign: EV-1
Spacesuit: EMU 3008 (red stripes)
Helmetcam: No. 18
Hometown: Jacksonville, N.C.
Education: Master's degree in electrical engineering
Hobbies: Backpacking, rock climbing, sailing
Launch (first space flight): Soyuz MS-12/58S, 3/14/19, Baikonur Cosmodrome, Kazakhstan
Landing (planned): Soyuz MS-13/59S, 02/06/20, Kazakhstan
Mission duration (planned): 328 days (female single flight world record)
Jessica Meir, Ph.D., 42Astronaut Jessica Meir during training at the Johnson Space Center in Houston. NASA
Will be the 15th woman to walk in space
Previous EVAs: None
Spacewalk call sign: EV-2
Spacesuit: EMU 3004 (no stripes)
Helmetcam: No. 11
Hometown: Caribou, Maine
Education: Master's degree in space studies, Ph.D. in marine biology
Hobbies: Skiing, hiking, running; private pilot
Launch (first flight): Soyuz MS-15/61S, 9/25/19, Baikonur Cosmodrome, Kazakhstan
Landing (planned): Soyuz MS-51/61S, 04/01/20, Kazakhstan
Mission duration (planned): 188 days
Friday's spacewalk will beThe 221st International Space Station spacewalk, or EVAThe 8th ISS EVA this year (7 by U.S., plus 1 Russian)The 3rd EVA for the Expedition 61 crewThe 4th EVA for KochThe 1st EVA for MeirThe 2nd EVA to replace a failed battery charge/discharge unit (BCDU)The 168th US/ISS EVA (Russian EVAs: 53)
Total spacewalkers to date: 227 (Meir will be the 228th)
Total female spacewalkers to date: 14 (Meir will be the 15th)
Total ISS EVA time logged to date: 1,381 hours and 12 minutes, or 57.6 days
List of female spacewalkersSvetlana Savitskaya, USSR; 1984Kathryn Sullivan, U.S.; 1984Kathryn Thornton, U.S.; 1992Linda Godwin, U.S.; 1996Tammy Jernigan, U.S.; 1999Susan Helms, U.S.; 2001Peggy Whitson, U.S.; 2002H. Stefanyshyn-Piper, U.S.; 2006Sunita Williams, U.S.; 2006 Nicole Stott, U.S.; 2009Tracy Caldwell Dyson, U.S.; 2010Kate Rubins, U.S.; 2016Anne McClain, U.S.; 2019Christina Koch, U.S.; 2019Jessica Meir, U.S.; 2019 (planned)Astronaut Christina Koch, visible near top center with a red stripe on her spacesuit, moves along the International Space Station's power truss during an Oct. 11 spacewalk to install new batteries for the lab's outboard solar arrays. NASA Why this spacewalk is necessary
The International Space Station is powered by four huge solar array wings, two on the left side of a football field-long truss and two on the right. The lab originally was equipped with 48 nickel-hydrogen batteries in four sets of 12 (one set per solar wing) to provide uninterrupted power when the space station is in the darkness of Earth's shadow.
To control battery charging in sunlight and discharging in darkness, each solar array wing, with its 12 nickel-hydrogen batteries, was equipped with six battery charge-discharge units, two per battery.
Because batteries lose their ability to recharge over time, NASA is in the process of replacing all 48 nickel-hydrogen batteries with 24 more powerful lithium-ion power packs and circuit-completing "adapter plates" to fill in where older batteries were removed but not replaced. In the upgraded system, each lithium-ion battery is charged and discharged by a single BCDU.
In 2017, spacewalkers replaced the 12 right-side inboard solar array batteries with six lithium-ion units. Last March, the 12 left-side inboard batteries were replaced. NASA currently is working to replace the left-side outboard batteries. The final set of lithium-ion batteries will be installed in the right-side outboard arrays next year
Three of six lithium-ion batteries were installed on the left outboard array during spacewalks by Koch and Morgan on Oct. 6 and 11. Shortly thereafter, engineers discovered one of the three BCDUs in that circuit had failed, reducing the power output by up to 5 kilowatts. Work to install the three remaining batteries was put on hold pending resolution of the BCDU issue.
The failure is troubling because an identical charger failed last March after a new battery was installed for the left inboard array. Only three spares are available, and NASA engineers want to make sure a generic problem of some sort is not present before proceeding with additional battery installations.