How do spacesuits keep astronauts alive?

It’s probably best to think of a spacesuit not as an item of clothing – like a jumper you’d put on when it’s cold or a pair of wellies to keep your feet dry – but as a habitat or a small personal spaceship astronauts wear. Two of the main threats to human life in space are the lack of oxygen and the extreme range of temperatures, which can fluctuate from below -100 degrees Celsius (-150 degrees Fahrenheit) to in excess of 120 degrees Celsius (242 degrees Fahrenheit). But they can face other dangers, too: the extremely low pressure, micrometeorites travelling several times the speed of a bullet and exposure to high levels of radiation, unfiltered by any planetary atmosphere like Earth’s, travelling from the Sun and deep space.

Astronauts need protection from these dangers while on an extravehicular activity (EVA) in space, so the modern spacesuit is designed to do just that. The outer section is divided into several main pieces with flexible and rigid parts, designed to provide mechanical protection from impact and a pressurised, oxygenated environment within the suit.

Underneath that, the astronaut wears a garment that helps regulate their body temperature with tubes that are woven into it, inside which water circulates for cooling. The astronaut’s chunky backpack carries the primary life support subsystem, which pumps the oxygen into the astronaut’s helmet for them to breathe and ‘scrubs’ the excess carbon dioxide out of the air they exhale. It also holds the electricity supply required to run the suit’s systems and a water tank for the cooling system.

How do spacesuits work?

The Z-suit

NASA's Z-suit
NASA’s Z-suit

NASA’s prototype Z-suit is a work in progress on an update to the current incarnation of the spacesuit, whose basic structure has been used for 30 years, ever since the Extravehicular Mobility Unit (EMU) was first made in 1981. At a glance, it doesn’t look radically different to contemporary space suits, but it’s been designed to include several key features that will allow it to be used in both the microgravity of space and for future missions to planets such as Mars, which the Apollo-era spacesuit isn’t capable of. It can be quickly put on and taken off (current spacesuits can take an hour or more to put on) and include a suitport dock, which replaces the airlock on a spacecraft. This means the spacecraft and space suit would be kept at the same pressure, so astronauts wouldn’t need to pre-breathe oxygen for at least 30 minutes before an EVA as they do now to prevent decompression sickness.

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Plus take a look at:

An interview with an astronaut 

Top 5 facts about weird astronaut training 

Why do astronauts train underwater?