Walking in space is a daunting enough task but the bulky design of the 127-kilogram suit makes it even tougher.
They wear extravehicular activity suits, commonly known as EVA suits, that allow them to breathe in the vacuum of space while protecting them from a harsh environment with temperature extremes and the risk of radiation damage.
But the complicated design of these suits has not changed since the 1980s, with astronauts often complaining about how difficult it is to perform tasks while wearing them.
“It is almost like you are putting on a different person when you get into the suit,” Kate Rubins, the 60th woman to go to space, said in a podcast by The Economist last week.
“So, it is like squeezing yourself through the smallest hole you can possibly fit … You also almost do the thing where you double-join your elbows to get your elbows through. That is actually kind of problematic, and we have had a lot of suit injuries just from donning and doffing this suit.”
She told the British weekly magazine that fixing panels on the ISS was similar to “doing car repairs while wearing stiff oven gloves and standing on a skateboard”.
How does the EVA suit work?
The suit is made of up several pieces, including a hard upper torso that covers the astronaut’s chest, an arm assembly piece that covers the arms and connects to bulky gloves. A lower-torso component covers the astronaut's legs and feet.
A helmet, which comes with an extravehicular visor to allow the astronaut to see as much as possible, protects the head.
There are flexible parts in the suit that are made up of several layers of material, which keeps oxygen within the spacesuit.
“On the back of the spacesuit is a backpack called the 'primary life support subsystem',” said Nasa on its website.
“This backpack contains the oxygen that astronauts breathe during a spacewalk. It removes carbon dioxide that astronauts exhale. The backpack also provides electricity for the suit.
“A fan moves the oxygen through the spacesuit and life support systems, and a water tank holds the cooling water that flows through the 'liquid cooling and ventilation garment'.”
The garment is underneath the spacesuit, with tubes woven into a tight-fitting piece of clothing that covers the entire body, except the head, hands and feet.
Water flows through these tubes to keep the astronaut cool during the spacewalk.
The back of the suit also has a device called the “simplified aid for extravehicular activity rescue”, which has several small thruster jets that an astronaut can use to fly back to the space station in the event they become untethered.
What is the problem?
While it sounds as if this design is flawless, the suit has actually put astronauts in life-threatening situations.
One incident was in 2013, when water leaked into the helmet of Italian astronaut Luca Parmitano during a spacewalk.
His eyes, nose and ears and part of his mouth were filled with water, but he managed to return to the airlock in time.
Once he was safely inside, he and his colleagues discovered that 1.5 litres of water had filled the helmet.
The spacewalk, which was meant to be 6.5 hours long, was cut short after only about 45 minutes.
Last June, a spacewalk by French astronaut Thomas Pesquet and Nasa astronaut Shane Kimbrough was cut short because there were issues with their spacesuits.
About three hours into the spacewalk, Mr Kimbrough lost data on his spacesuit’s display unit, and then there was a sharp increase in the pressure reading on his spacesuit.
They were supposed to install a new set of solar arrays on the station but the trip was cut short after a nearly seven-hour spacewalk.
Nasa is working towards developing next-generation spacesuits for spacewalks outside of the space station and for future crewed missions to the Moon under the Artemis programme.
The space agency wants to work with commercial partners, rather than build them in-house with traditional government contracts.
It wants to develop the xEVA system, or exploration extravehicular activity suits, that would be used in future missions.
“Nasa needs xEVA suits and capabilities to support the International Space Station and lunar surface missions under Artemis, which will bring humans back to the lunar surface for the first time since 1972,” the space agency said.
“One or more commercial partners, in collaboration with Nasa, will design, develop, build, assemble, test and maintain a fleet of flight and training xEVA equipment.
“This includes spacesuits and associated hardware to be used during Artemis missions on the lunar surface and at the Gateway lunar-orbiting outpost, as well as on the International Space Station.
“The commercial partner(s) also will train crew members and manage their xEVA system hardware during spacewalks. This approach continues Nasa’s focus on International Space Station commercial services and is a logical next step.”