Two American astronauts Jessica Meir and Christina Koch are ready to set off on a mission today at 5.20 pm IST, Friday evening. They are scheduled to carry out the historic spacewalk from the International Space Station that marks the 221st spacewalk, the mission marks the first time after 220 spacewalks that two women astronauts for the first time in history will be carrying it out.
According to NASA the spacewalk is necessary to assemble, maintain and upgrade the Space Station that 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. The space station is equipped with a 48 nickel-hydrogen (Ni-H) battery, (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.
As the space stations several charge-and-discharge units (called “BCDUs”) connecting the batteries failed and 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.