Suit up17 August 2020

ESA (European Space Agency) astronaut Luca Parmitano is pictured attached to the Canadarm2 robotic arm while finalizing thermal repairs on the Alpha Magnetic Spectrometer, a dark matter and antimatter detector, during a spacewalk. Credit: NASA

The International Space Station is a modular space station in the low Earth orbit and just like industrial, commercial and domestic facilities across our planet, it typically needs to be maintained, repaired and upgraded by its residents. External tasks call for some serious personal protective equipment

On Saturday 30 May this year, NASA astronauts launched from American soil in a commercially-built and -operated American crew spacecraft for the first time ever. The SpaceX Crew Dragon spacecraft, carrying NASA astronauts Robert Behnken and Douglas Hurley, lifted off on the company’s Falcon 9 rocket at NASA’s Kennedy Space Center in Florida, US. The mission: an end-to-end test flight to validate the SpaceX crew transportation system, including launch, in-orbit, docking and landing operations (

A mere 19 hours later – on Sunday 31 May – the crew successfully docked at the International Space Station (ISS).

The ISS is a large spacecraft in orbit around Earth that serves as a home and research facility for astronauts (people trained and certified by NASA, the European Space Agency (ESA), Canadian Space Agency, or Japan Aerospace Exploration Agency) and cosmonauts (people trained and certified by the Russian Space Agency).

The first piece of the station was launched into space in November 1998 and construction was finally completed in 2011. It includes laboratory modules and living areas, as well as solar arrays for collecting energy from the sun to provide electrical power, radiators for temperature control, docking ports for spacecraft, and airlocks to allow the astronauts to conduct spacewalks (see small box out for more ISS details).


The latter – spacewalks – are an important activity as they allows residents to carry out maintenance, repairs and upgrades to the external aspects of the station ( Damage may have occurred from space debris, for example, or external equipment may be in need of an upgrade.

In-fact, four astronauts ventured outside of the ISS for three spacewalks in January this year to complete battery upgrades and finalise repairs to a cosmic ray detector. Expedition 61 flight engineers Jessica Meir and Christina Koch of NASA conducted spacewalks to replace nickel-hydrogen batteries with new lithium-ion batteries that store power generated by the station’s solar arrays. NASA astronaut Andrew Morgan and space station commander Luca Parmitano of ESA then finished installing the Alpha Magnetic Spectrometer’s (AMS) new cooling apparatus (

And at the end of June and start of July, NASA astronauts Chris Cassidy and Behnken (of the SpaceX Crew Dragon, pictured below) also conducted spacewalks to again replace aging nickel-hydrogen batteries with new lithium-ion batteries (

NASA astronaut Bob Behnken is pictured during a spacewalk to swap batteries and upgrade power systems on the International Space Station's Starboard-6 truss structure. Behnken was joined during the six-hour and seven-minute excursion by NASA astronaut Chris Cassidy (out of frame). Credit: NASA


Undertaking spacewalks to conduct external work to the ISS, such as those mentioned above, would not be possible without appropriate personal protective equipment (PPE), also known as an Extra-Vehicular Activity (EVA) suit or Extra-Vehicular Mobility Unit (EMU) ( Astronauts that partake in a spacewalk face many dangers – from dust and debris, to radiation, extreme temperatures (ranging from -155°C (-250°F) to 121°C (250°F)) and lack of oxygen – so these suits provide a means of survival when venturing ‘outside’. They are, in essence, miniature spaceships.

Before we get into the details though, it is important to note that the spacewalk suit is not worn in the spacecraft on the way up to, or down from, space. Instead astronauts wear a different kind of suit for launch, ascent, re-entry and landing. That is not covered here.

The spacewalk suit has two main parts – the pressure garment, which consists of various components (detailed below) and the life support system. The former is the human-shaped portion of the space suit that so many would have seen from photographs and videos over the years. It effectively protects the body and enables mobility.

The most inner part of the pressure garment is a cooling garment that covers the entire body except for the head, hands and feet. It is made of a stretchy spandex material with around 300 feet of woven-in water tubes. Within these tubes flows chilled water to regulate body temperature and remove extra heat during the spacewalk. Vents in the garment also draw sweat away and help with air circulation.

The hard upper torso of the suit is made of fibreglass and connects the inside of the suit with the appropriate systems in the portable life support system (see below). It is shaped like a sleeveless shirt and connects to the arm assembly that covers the arms and joins the heated gloves. As the astronauts do not wear custom-made suits, different sizes of arm assembly parts are available with sizing rings allowing the arm parts to be made longer or shorter.

The lower torso section, meanwhile, consists of spacesuit trousers, boots and the lower half of the waist closure. A metal body-seal closure connects the lower torso to the hard upper torso. D-rings are also present so that tethers (cords) can be attached to the station when conducting a spacewalk to stop the astronauts from floating away.

Finally, there is the headgear, which consists of a communications system and helmet. The communications system features a cap – often referred to as a ‘Snoopy’ cap because of its resemblance to the aviator cap worn by the cartoon character – as well as earphones and microphones. These components connect to a radio on the suit and enable the astronaut to communicate with mission control and crew members. Changes to the design are also being introduced with the next generation spacesuit for the Artemis generation of astronauts (see box for more information).

The helmet serves as a pressure bubble and is made of ‘strong plastic’ to keep the pressure of the suit contained. It also has a ventilation system to provide oxygen to the user, a small foam block to scratch the nose, and a protective visor on the outside of this bubble to keep the pressure bubble from getting bumped or scratched. Furthermore, there is also a sun visor and movable sun shades. The former has a gold coating that works like the astronaut's sunglasses. Both, together, provide protection from the sun's strong rays.

In total, the spacewalk space suit is constructed from as many as 16 layers of material that all perform different functions: the cooling garment makes up the first three layers, followed by the bladder layer, which is filled with gas to create proper pressure for the body, and holds in the oxygen. The next layer holds the bladder layer to the correct shape around the astronaut's body while the ‘rip-stop liner’ acts as a tear-resistant layer. The next several layers are insulation and act like a thermos to help maintain the temperature inside the suit, while the white outer layer reflects heat from sunlight and is made of a fabric that blends three kinds of threads (one thread provides water resistance, another is used to make bullet-proof vests, and the third is fire-resistant).


Of course, what has been mentioned above only makes up one of the main parts of the spacewalk suit. Indeed, the second part – the life support system, which is housed in a backpack – is just as critical.

This backpack houses the supplies and equipment to make the suit work. It includes the oxygen that astronauts breathe and that pressurises the suit, as well as a regulator to keep the suit at the correct pressure. A fan also circulates oxygen through the suit and life support system where the carbon dioxide that astronauts exhale is removed from the suit.

In addition, the backpack also provides electricity for the suit and holds the communication radio, water for the cooling garment, a chiller to cool the water and a pump that circulates the chilled water.

The longest spacewalk that has ever been conducted lasted eight hours and 56 minutes and was performed by NASA astronauts Jim Voss and Susan Helms in 2001 as they worked on the ISS. But any spacewalk – regardless of its length of time – can be a gruelling task.

Luckily, there are also some additional components that astronauts can use for health and safety purposes, as well as the task at hand ( They include:

  • In-suit drink bag: This plastic, water-filled pouch attaches to the inside of the hard upper torso and allows the user to drink (stopping dehydration). The user bites down on a valve, which is connected to a plastic tube, releasing the drinking fluid
  • Maximum absorption garment: This adult-sized nappy absorbs material under the spacesuit
  • Cuff checklist: Worn on the wrist, this checklist provides a breakdown of the tasks to be carried out on the spacewalk
  • Simplified Aid for EVA Rescue (SAFER): Similar to a life jacket, spacewalk astronauts also wear SAFER as a safety precaution. If an astronaut should become untethered and float away, the system can help him or her fly back to the station. It uses small nitrogen-jet thrusters and is controlled by a small joystick.

Spacewalk space suits are complicated pieces of PPE, but make sense when broken down into functions. The main purpose of any PPE is, of course, to protect the wearer – and with so many additional health and safety factors in space, it is easy to see why this kit has been so successful in enabling astronauts to conduct external tasks around the ISS. Health and safety is, and will always be, a critical factor across industry, and that focus applies everywhere – even 250 miles up in the sky.

Box out 1: ISS statistics

  • The ISS orbits Earth at an average altitude of approximately 250 miles
  • The ISS travels at 17,500 mph and orbits Earth every 90 minutes
  • The first crew arrived on at the ISS on 2 November 2000
  • The ISS cover the area of an American football field
  • The ISS has the volume of a five-bedroom house or two Boeing 747 jetliners
  • The ISS can support a crew of six people, plus visitors.

Source: NASA (

Box out 2: Kitting up the Artemis generation astronauts

NASA’s Artemis programme is aiming to land the first woman and next man on the Moon by 2024. Using ‘innovative’ technologies, the aim is to explore more of the lunar surface than ever before and use those learnings to take the next giant leap – sending astronauts to Mars.

The new suit that will be worn on Artemis missions is called the Exploration Extra-Vehicular Mobility Unit (xEMU). It shares most of the same basic elements as the current spacewalk suit but also includes several new features and technological advances, such as:

  • A suite of dust-tolerant features to prevent inhalation or contamination of the suit’s life support system
  • Miniaturised electronics and plumbing systems, making it possible to build-in duplicates for much of the life support system – increasing safety and making some failures less of a concern
  • A new lower torso made from ‘advanced materials’ and joint bearings that allow bending and rotating at the hips, increased bending at the knees, and hiking-style boots
  • Shoulder enhancements so arms can more freely and easily lift objects
  • A redesigned communications system that scraps the Snoopy caps and replaces them with a new audio system that includes multiple, embedded, voice-activated microphones inside the upper torso that automatically pick up the astronaut’s voice
  • A rear-entry hatch to allow astronauts to climb into a spacesuit from the back of the suit, as well as a quick-swap protective visor on the helmet.

Source: NASA (

Adam Offord

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