Nasa’s two ‘stranded’ astronauts will get a trip outside this week, having spent over seven months in orbit unexpectedly.
They will leave the International Space Station for a surprise spacewalk together on Thursday, which will be Butch Wilmore’s first time outdoors since his ride home malfunctioned last June.
His partner Sunita Williams, now commander of the station having only intended to stay eight days, will be doing her second spacewalk in the space of around a week.
They will carry out repairs and collect samples to see if microorganisms exist on the exterior of the station.
Butch and Suni are seen by some as space castaways, but they’re super-skilled professionals and will be taking on the mission every astronaut dreams of before their return trip is finally due this spring.
But what does a space walk actually involve, and how risky is it?
Dr Kirsty Lindsay, assistant professor of Aerospace Medicine at Northumbria University and an expert in astronaut health, told Metro that space walks are like the ‘heaviest gym session’ you could have on earth.
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It’s not a case of floating around admiring the view: You will be wearing a heavy, bulletproof, pressurised suit, while doing tricky manouevres and breathing canned air, for six to eight hours without food and with only limited water.
As well as the physical challenges, the mental impact can be profound – especially after being inside for months.
Dr Lindsay said: ‘If you think about how everyone was feeling in 2020 when we all got stuck in the house [during the Covid-19 lockdowns], how nice was it when we were told you can go out for your constitutional walk and have some fresh air?
‘Going for a spacewalk, an EVA, is the astronaut equivalent.’
Something astronauts often describe after a spacewalk is the Overview Effect, a state of awe and connection where they look at Earth against space’s blackness and suddenly have a new understanding of it as a whole, fragile world.
‘I imagine that the first moment coming out of the ISS is going to be wonder and excitement, but also professional focus,’ Dr Lindsay said.
For Butch, it will be his first time outside in months, and not only outside but floating in space.
For Suni, she may still be feeling sore from her previous spacewalk, which will have been physically punishing, on top of the effects on the body which come from being in microgravity in general.
They will probably have a lighter workload the day before, to allow them to rest and prepare.
Before stepping outside the ISS, Suni and Butch will have to prepare to be in an environment with much less pressure, so will have to breathe 100% oxygen in a special airlock compartment, to reduce the risk of them getting the Bends like deep sea divers, when nitrogen forms bubbles in the blood and tissue.
Once they are outside, they will be in constant radio communication with their partner spacewalker and with their buddy inside, but will be working essentially alone.
Dehydration can be a problem, with astronauts having only a limited amount of water to drink while sweating profusely.
Their heart rates will be constantly monitored so that if they start showing signs of stress, they can be pulled back inside.
The other big thing Nasa is careful of is vertigo and dizziness, which can happen as astronauts come out of the airlock.
‘There can be a change of perspective because of where you see the globe. It feels like you’re falling endlessly into space,’ Dr Lindsay explained.
To combat this, part of the ISS such as a solar panel is rotated so it is always in view beneath them so they have something as a floor reference to anchor their vision: ‘You don’t want to throw up in a space suit.’
Nasa astronauts Suni Williams and Butch Wimore
Sunita Lyn ‘Suni’ Williams
- Age: 59
- Total spacewalks: 8 (the second highest number by a woman)
- Total spacewalk time: 56 hours and 40 minutes
Barry Eugene ‘Butch’ Wilmore
- Total spacewalk time: 25 hours and 36 minutes
Both astronauts are veteran pilots of the US Navy.
They took on the first crewed mission of the Boeing Starliner in June 2024, but due to concerns over its safety, it came back to Earth without them.
They will fly home on a SpaceX Crew Dragon capsule, which will return to the ground via splashdown.
Another worry is the presence of micrometeoroids, which could possibly smash into the space suit and puncture it.
The risk is illustrated by craters and holes seen sometimes on the ISS exterior, but there has never yet been an incident of one hitting an astronaut.
Tracking stations on earth monitor every space rock in the area larger than 1cm, and the spacewalk is scheduled to avoid any that threaten to come close.
There is an emergency procedure if an astronaut is hit, however. The spacesuit is designed to immediately seal up around the impact site so the damage is localised.
It is also designed to resist impact in the first place, with heavy-duty Kevlar, as well as to protect from radiation.
‘I’ve been told it’s quite a relief to get the suit off,’ Dr Lindsay said. ‘They’re often sweaty because they’ve been working really hard, so they have to dry the inside of the suit with cloth.
They’ll have a food break, and a toilet break. Then they’ll put their suits away.’
Of course, with spacewalks lasting six to eight hours, they may have needed to use the loo while out there.
If they did have to go to the toilet during the spacewalk, they will also have to deal with their Maximum Absorbency Garment (essentially, a space nappy).
‘The rule is if you use it, you tidy it up,’ Dr Lindsay said.
The following day will be a quiet day where they can rest, phone home, and do some light exercise as active recovery.
Spacewalks which went wrong
Most spacewalks go to plan, reflecting the extremely detailed risk assessment and planning beforehand – but some have had problems.
When Russian cosmonaut Alexei Leonov performed the first spacealk in 1965, crew had not realised that his suit would expand in the vacuum of space.
It swelled so much that he couldn’t squeeze back inside the airlock, and his body temperature increased putting him at risk of heatstroke. He managed to release some of the air and get safely back inside, and amendments were made to space suits to avoid this happening again.
In 2013, Nasa astronaut Luca Parmitano nearly drowned in space when his suit malfunctioned.
A litre and a half of water flooded into his helmet due to a clogged filter, and he had to rapidly make his way back into the airlock as the liquid reached his ears and nose.
While Suni and Butch were not expecting to be in space for so long, it is not unusual for astronauts to spend so long on the ISS.
In fact, the length of time spent there has lately been getting longer, Dr Lindsay said, because our ambitions for space travel are changing.
A place to live and work in orbit around the Moon is currently being developed with the Gateway space station.
Going to Mars is also a target, with Elon Musk hoping his Starship rocket will be the first one to take us there.
‘People are going to be spending longer and longer in space,’ Dr Lindsay said, so it is important we learn about the effects of longterm residence there.
An unplanned mission like the one Suni and Butch are currently conducting will also help us learn more about how to respond in future missions which go beyond Low Earth Orbit and cannot be entirely planned from the ground, on to Mars or potentially even further beyond.
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