Insulation in Space – How do Astronauts Keep Warm?


Space suits have to be designed to cope with extreme temperatures. Depending on the position of the sun, temperatures can plunge to -233°C (-387°F) or soar to reach around 135°C (275°F), so the suit needs to be very well insulated to be able to cool and warm the astronaut, as needed.

A huge amount of research goes into new suit designs and developing improvements to enable the astronaut to be more comfortable and have better mobility. This is crucial to the astronaut as they routinely perform fiddly repair jobs both inside a craft and when they are outside on a spacewalk or, to use the technical term, an EVA (Extra-Vehicular Activity). EVA suits need to protect the wearer from the conditions in the space environment, maintaining a safe pressure, temperature and oxygen supply, and shielding against water, fire and small space objects that could harm the astronaut.

The space suit design currently used by NASA has 14 layers of material and takes 45 minutes to put on. Materials include ortho-fabric, aluminised mylar, neoprene-coated nylon, dacron, urethane-coated nylon, tricot, nylon/spandex, stainless steel, and high-strength composite materials. After ‘donning’ their suit, an astronaut must spend over an hour breathing oxygen inside it to adjust to the lower pressure.

Over this LCVG, the next layer of the suit is called the bladder layer, which maintains the correct pressure in the suit and holds oxygen. Over this, a layer of material like that of a camping tent holds the bladder layer in place. Next is the tear-resistant ripstop liner, followed by seven layers of Mylar insulation. All these layers enable the suit to keep a constant temperature inside, working like a thermos. They pad the suit and protect it from damage by flying objects in space.The astronaut’s body temperature is carefully controlled. The liquid cooling and ventilation garment (LCVG) sits closest to the body and makes up the first three layers of the suit. It keeps the astronaut cool with 91.5m (300ft) of narrow tubes that circulate chilled water, which carry heat away from the body. Sweat is removed through vents and recycled back into the water-cooling system. To boost circulation in the suit, the stretchy spandex garment pulls in oxygen at the wrists and ankles.Space suits are made up of interlocking parts, which rotate around bearings and allow the astronaut to move around more easily. The parts also mean suits are more customisable to the individual, as pieces can be put together of the size required, rather than making full suits in different sizes. The main parts of a suit are: a liquid cooling and ventilation garment (thermo-regulating space underwear), a helmet, gloves, soft lower torso assembly, upper torso, hard upper torso vest, arm assembly, and maximum absorption garment (space nappy for long spacewalks). On top of this, the astronaut carries a lot of gear  – displays, life support, a joystick-controlled emergency jetpack (called a SAFER), a drink bag, communicators, and even a cuff checklist of things to do in space – out with him on spacewalks. The suit needs to be fully equipped so it is basically a personal spacecraft.

A blend of three fabrics make up the outermost layer of the suit, the Thermal Micrometeoroid Garment: one is waterproof, another is fire-resistant, and the third is the same sturdy material used to make bulletproof vests. It insulates, protects against solar radiation and minimises damage done to the suit or wearer by micrometeoroids or other orbital debris.

The Helmet

EVA Gloves
A space helmet does the important task of covering the astronaut’s head, and regulating the oxygen pressure inside. It has a vent pad which directs oxygen from the life support subsystem and hard upper torso. The clear bubble is a familiar feature on a space suit, and allows the astronaut to see what they are doing. It is covered by a visor to shield against extreme temperatures and small objects in space, and a thin layer of gold to filter out dangerous solar rays. The helmet can be fitted with a TV camera and lights as well.

Hand fatigue and injuries are a very common problem for astronauts, and, according to one report, they have made up around 47% of all recorded injuries in the last twenty years. New technologies are in constant development to address this, like robotic mechanisms in the glove to reduce the strain on astronauts’ hands. This is especially relevant for deep space exploration to other moons and planets, as the current design is not fit for use in environments other than ones relatively free of debris, asteroids and dust.It is important for a suit to pay attention to the fingers, since these get the coldest in space. On a spacewalk, an astronaut might be carrying out tricky repairs or measuring with small instruments, so the gloves need to balance safety and protection from the elements with functionality and mobility. The gloves above connect to the sleeve by a bearing that allows the astronaut to turn their wrist, and are fitted with thermofoil fingertip heaters. Astronauts also have the option of wearing ‘comfort gloves’ and adjustable thermal mittens to guard against extreme cold.

The Apollo space missions needed 15 space suits each: the three members of the prime crew used three suits each, one for training, one for flight, and one back-up; and the three-man back-up crew also had a suit each for training, and one for flight.

Fun facts:

  • Space suits are white to reflect heat into space, but they have stripes around the knees, usually red or candy cane patterned, so spacewalkers can tell each other apart.
  • Putting on a suit is called ‘donning’, whereas taking it off is called ‘doffing’. Astronauts need special ‘donning handles’ to pull their space trousers up.
  • A spacesuit weighs around 127kg (280 pounds) on the ground – in space, with microgravity, it weighs nothing!


Naomi Pyburn

Naomi is an English graduate with an itch to write. Her free time is spent blogging, reading feminist writing, cycling, cooking and managing her food Instagram account. Her not-so secret talent is the ability to nap anywhere.

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Last modified: 16th April 2018