Astronauts Christina Koch and Jessica Meirfor 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 thein 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, 40
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 Hague
- 10/06/19: 7 hours 1 minute; solar array battery replacement (right outboard array); with Drew Morgan
- 10/11/19: 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., 42
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 be
- The 221st International Space Station spacewalk, or EVA
- The 8th ISS EVA this year (7 by U.S., plus 1 Russian)
- The 3rd EVA for the Expedition 61 crew
- The 4th EVA for Koch
- The 1st EVA for Meir
- The 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 spacewalkers
- Svetlana Savitskaya, USSR; 1984
- Kathryn Sullivan, U.S.; 1984
- Kathryn Thornton, U.S.; 1992
- Linda Godwin, U.S.; 1996
- Tammy Jernigan, U.S.; 1999
- Susan Helms, U.S.; 2001
- Peggy Whitson, U.S.; 2002
- H. Stefanyshyn-Piper, U.S.; 2006
- Sunita Williams, U.S.; 2006
- Nicole Stott, U.S.; 2009
- Tracy Caldwell Dyson, U.S.; 2010
- Kate Rubins, U.S.; 2016
- Anne McClain, U.S.; 2019
- Christina Koch, U.S.; 2019
- Jessica Meir, U.S.; 2019 (planned)
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.