First all-woman spacewalk starting 5.20 pm today: What will Koch and Meir do on the historic mission?

The mission marks the first time after 220 spacewalks that two women astronauts will embark on such a mission.

Two American astronauts are scheduled to carry out a historic spacewalk from the International Space Station on 18 October. While the mission marks the 221st spacewalk overall, both astronauts carrying it out will, for the first time in history, be women.

Astronauts Jessica Meir and Christina Koch are due to set off on this mission at 5.20 pm IST Friday evening. The spacewalk is part of a regular series of assembly, maintenance and upgrade missions to the space station, and the eighth such spacewalk outside the station in 2019.

Astronauts Christina Koch and Jessica Meir will be on the first woman-only spacewalk. image credit: Twitter/NASA

Astronauts Christina Koch and Jessica Meir will be on the first woman-only spacewalk. image credit: Twitter/NASA

Why is the spacewalk necessary?

The Space Station is powered entirely by four giant solar panel arrays – two on the left of the main passage (called a "truss" in spaceflight lingo), and two on the right. When the orbiting lab was first integrated, it was equipped with 48 nickel-hydrogen (Ni-H) batteries (12 for each solar wing) for providing uninterrupted power when the space station periodically falls under the Earth's shadow.

Like a switch to control charging (in sunlight) and discharging (in darkness), every solar array and its 12 Ni-H batteries are equipped with two charge-discharge units per battery. In a series of upgrades, NASA is giving the electronic power supply of the space station a major upgrade.

Apart from replacing the batteries with more powerful ones, the charge-discharge unit is also being simplified – with every one of the 24 new Li-ion batteries controlled by a single unit.

Flight engineer and astronaut Christina Koch replacing a battery on her 11 October spacewalk. NASA

Flight engineer and astronaut Christina Koch replacing a battery on her 11 October spacewalk. Image: NASA

On two earlier spacewalks (6 and 11 October), astronauts Koch and Morgan replaced three of the six Li-ion batteries on the station's left-side solar panel arrays. But space is hard, and space tech rarely functions exactly as it was meant to. In the present case, trouble came calling when the charge-and-discharge units (called "BCDUs") connecting the batteries failed – and not just in one battery, but several of them.

Before any additional battery installations, NASA wants to ensure the problem isn't a generic one affecting all the Li-ion batteries manufactured before installing any more of them. On 18 October, Koch and Meir will exit the station’s "Quest" airlock and try to replace the failing power controller unit on their spacewalk.

While one of the faulty BCD units has already been returned to Earth for examination, NASA engineers are waiting to find out if the same problem is affecting all the faulty BCD units. This will only be possible in a few months when a second BCD unit will be returned to Earth in a SpaceX Dragon capsule for troubleshooting.

Why is the all-women spacewalk so significant?

The 18 October spacewalk marks the first time (after 220 spacewalks!) that two women astronauts will embark on a spacewalk as a pairing. Meir, who will be on her maiden spacewalk in this mission, will be the 15th woman overall and the 14th American woman to spacewalk since cosmonaut Alexey Leonov's made history with the first one 54 years ago.

For Koch, this isn't her first, but her fourth spacewalk so far. The spacewalk was originally planned for 29 March, but was postponed indefinitely when NASA made a "change in the astronauts to protect the safety of the crew and the timing of the mission."

(Also Read: NASA scraps all-women spacewalk because of a lack of well-fitted at the ISS)

Without a configured spacesuit that fit astronaut Anne McClain, she had to swap places with astronaut Nick Hague on the subsequent spacewalk planned for 8 April 2019. This decision was made by McClain herself, according to NASA, so that "everyone could wear spacesuits that fit them best."

Koch and Meir, who were both selected as candidates in 2013, are currently on their first-ever spaceflight together. Once the spacewalk is complete, Koch will continue working at the space station till her planned 11-month mission is complete. While the all-woman spacewalk wasn't planned as such, Koch's mission at the space station is the first concrete step taken towards understanding how space affects the health of women in space for long periods of time. NASA is keen to study this (and quickly) ahead of its upcoming human moon mission Artemis in 2024.

Astronaut Koch in uniform. Image: NASA

Astronaut Christina Koch in uniform. Image: NASA

The spacewalking women hall of fame

Till the planned milestone on 18 October, there have been fourteen women from both the USA and USSR have carried out spacewalks.

Svetlana Savitskaya, for USSR in 1984

Kathryn Sullivan, for USA in 1984

Kathryn Thornton, for USA in 1992

Linda Godwin, for USA in 1996

Tammy Jernigan, for USA in 1999

Susan Helms, for USA in 2001

Peggy Whitson, for USA in 2002

H Stefanyshyn-Piper, for USA in 2006

Sunita Williams, for USA in 2006

Nicole Stott, for USA in 2009

Tracy Caldwell Dyson, for USA in 2010

Kate Rubins, for USA in 2016

Anne McClain, for USA in 2019

Christina Koch, for USA in 2019

Jessica Meir (planned), for USA in 2019

Find latest and upcoming tech gadgets online on Tech2 Gadgets. Get technology news, gadgets reviews & ratings. Popular gadgets including laptop, tablet and mobile specifications, features, prices, comparison.