ESA astronaut Thomas Pesquet and NASA astronaut Shane Kimbrough will exit the International Space Station on Friday 13 January on a spacewalk to upgrade the Station’s power supply. A carefully planned and detailed affair all spacewalks require coordination and lots of work from many people on ground support.
New lithium-ion batteries arrived on the Space in December on the Japanese cargo ship HTV-6 and the batteries have been moved using the Station’s robotic arm operated from Earth into place on the Space Station’s power channels. Six new batteries arrived on the Space Station to replace the older nickel-hydrogen batteries. One Li-On battery replaces two older batteries – an adapter plate is installed in one of the free slots and the plate also acts as storage for one of the nickel-hydrogen batteries being replaced – the other nickel-hydrogen battery is returned to HTV-6 where it will be trashed.
Thomas and Shane’s spacewalk this week is the second to install the batteries. NASA astronaut Peggy Whitson and Shane spent six hours and 32 minutes outside installing adapter plates and connecting three of the six new batteries on Power channel 3A on Friday 6 January. For this spacewalk Thomas and Roscosmos astronaut Oleg Novitsky helped Peggy and Shane suit up.
This week’s spacewalk “EVA39” will see Thomas and Shane work on power channel 1A, but only leave one old battery on an adapter plate.
The six-hour spacewalk needs to be thought through in detail and is choreographed minutely. Every detail, down to the order in which tools and equipment are attached to the astronaut’s suits is worked-out in advance.
On the day itself, Thomas and Shane will start “prebreathing” up to two hours before they start the spacewalk. The pressure inside their so-called EMU suits is lower than the Space Station which is pressurised at sea level. Similar to scuba divers, astronauts would suffer from the ‘bends’: quickly changing pressure can nitrogen in human bodies to turn into bubbles with serious symptoms. To avoid this, astronauts breathe pure oxygen to purge their bodies of nitrogen.
Peggy and Oleg will help the spacewalkers into their suits, an ordeal in itself in weightlessness. Once suited up the duo will enter the Quest airlock and begin lowering the pressure. When they open the outside hatch, scheduled for 12:00 GMT, their spacewalk will officially begin.
Shane leaves the Station first, first order is to do a ‘buddy-check’ to make all equipment is as it should be and to orient themselves in this new environment. The astronauts must always be tethered to specific Space Station supports, much like rock climbers or cave explorers.
They frequently check their suits and especially their gloves that are the most fragile and come into contact with the most objects. Even a small hole in a pressurised spacesuit in space is not a good idea.
Shane will move to the power channel to prepare a foot restraint so he can hold on to the Station with his feet while Thomas goes to the HTV-6 pallet with the adapter plates. Thomas will release two adapter plates and attach one to himself and hand one to Shane who returns to collect the plate. The duo will then go to the power channel 1A and Thomas will hand his adapter plate to Shane for installation. They then remove the last old-type battery and install it on the adapter plate. With this done they will install the second adapter plate. By this time they should be around three hours into their spacewalk.
The third and last adapter plate is still on the external pallet from HTV-6 so Shane and Thomas will go and collect it to return and install it. They will then clean up and collect all the tools and the foot restraint and store it on the so-called CETA or Crew Equipment and Translation Aid before heading back to the airlock.
As spacewalks are complicated and time-consuming there are always extra tasks planned in case the astronauts have more time on their hand.
If time allows, Shane will head to the Space Station’s truss and retrieve a failed camera called the Camera Light Pan Tilt Assembly that was on the Station’s robotic arm. It will be retrieved and replaced with a new one for robotic installation later.
All these operations will take around six hours and 20 minutes when the spacewalkers will return to the airlock. For all this time there will be no food and no toilet break. Water is supplied in a pouch with a drinking straw. The work is tiring as the astronauts fight against the pressurised suit that becomes stiff in the vacuum of space. A spacewalk is a test of patience and alertness.
Throughout the spacewalk they will check their suit and especially their gloves for wear and tear. Every 90 minutes the Space Station orbits Earth so Shane and Thomas will be continuously working 45 minutes in daylight and 45 minutes in complete darkness. The spacesuits have lights for the dark moments, but as the Sun rises it can be blinding for moments.
After a 25 minute clean-up and further checks the airlock repressurises in around five minutes. Inside, Peggy and Oleg will be waiting to welcome them and help them out of their suits.
Live coverage starts at 11:30 CET (10:30 GMT) and can be followed via NASA TV or via CNES with French commentary here. The spacewalkers can be recognised by a red stripe on the suit. Shane will be “extravehicular crew member 1” or EV1 wearing a suit with red stripes while Thomas will be EV2 without strip. At Houston mission control in USA, ESA astronaut Luca Parmitano will be guiding the two spacewalkers over the radio. You will hear his voice on the live coverage. Follow the spacewalk on Twitter from @esaspaceflight in English and @CNES in French.