What are the parts of a space suit?
A space suit is really a small spacecraft shaped like a person. Every spacewalking suit has the same basic parts: a cooling garment worn next to the skin, a pressure garment that holds air around the body, protective outer layers, a helmet with a sun visor, gloves and boots, and a life support backpack that supplies oxygen, removes carbon dioxide, cools the astronaut and handles communications [1][2].
John Lawson’s cutaway diagram above shows these parts on the suit Apollo astronauts wore on the Moon, the A7L, with the backpack opened up to show what was inside. The sections below go through each part, how it worked on Apollo and how today’s suits on the International Space Station (ISS) compare.
Why astronauts need a space suit
Space is a vacuum with no air to breathe and huge swings in temperature. NASA lists what a suit has to do: supply oxygen to breathe, protect against temperatures that in Earth orbit run from about minus 157°C (minus 250°F) in shadow to about 121°C (250°F) in sunlight, shield against radiation and tiny fast-moving particles of space dust, and protect the eyes from bright sunlight [1]. It also carries drinking water for long spacewalks [1].
The lunar surface added more. The Apollo suits needed boots made for walking on rock and dust, and their own life support so astronauts could walk away from the lunar module [1].
The layers of a space suit
From the skin outwards, the Apollo A7L had three main garments:
- Liquid cooling garment. Lunar crews wore a three layer garment, a bit like long underwear, with plastic tubes running through it. Cool water flowed through the tubes to carry away body heat and reduce sweating and fogging of the helmet [3]. The diagram’s sleeve cutaway shows this tubing next to the skin.
- Pressure garment. A rubber bladder held the suit at about 3.7 psi (25.5 kPa), roughly a quarter of the air pressure at sea level, with joints built in so the astronaut could bend arms, legs and waist [3]. A zip ran from the neck ring down the back and round the crotch [3].
- Integrated Thermal Micrometeoroid Garment. The outer cover protected against heat from the Sun, abrasion and micrometeoroids. It had 13 layers, from rubber coated nylon on the inside, through aluminised Mylar, Dacron and Kapton, to fireproof Teflon coated Beta cloth on the outside [3].
Today’s ISS suit, the Extravehicular Mobility Unit (EMU), uses the same idea. Astronauts first put on a Liquid Cooling and Ventilation Garment, then the soft lower half of the suit, then a rigid chest piece called the Hard Upper Torso, which the backpack and arms attach to [1][4].
Helmet, visor, gloves and boots
The Apollo suit used a clear “fishbowl” helmet, chosen because it gave an unrestricted view and needed no visor seal [3]. Over it went an extravehicular visor assembly with a sun visor to protect the eyes from bright sunlight [1]. Gloves and helmet locked onto the suit with quick disconnect rings at the wrists and neck [3]. The boots and gloves had uppers of Chromel-R, a woven nickel chrome fabric that stood up to abrasion [3].
Under the helmet, astronauts wore a fabric communications headset known as the “Snoopy cap”, with earphones and microphones built in. ISS crews still wear one today [4].
The life support backpack
The backpack, which NASA called the Portable Life Support System (PLSS), is what lets an astronaut work without a hose to the spacecraft. On Apollo it did five jobs, all visible in the diagram’s backpack cutaway [5]:
- Oxygen. A primary oxygen tank supplied breathing gas and kept the suit pressurised.
- Carbon dioxide removal. A canister of lithium hydroxide absorbed the carbon dioxide the astronaut breathed out. The diagram describes this as separating carbon dioxide from oxygen; in fact the lithium hydroxide absorbs the carbon dioxide chemically and removes it from the breathing air [5].
- Cooling. A water tank and pump fed the cooling garment. The water was cooled by a sublimator, a metal plate with tiny pores that let a little water freeze, thaw and boil off into space, taking heat with it [3][5].
- Communications. A radio and antenna relayed voice and data through the lunar module to Earth [5].
- Emergency backup. A separate Oxygen Purge System sat on top of the backpack, just behind the helmet. If the main system failed, it kept the suit pressurised and flushed out carbon dioxide and heat with a steady flow of oxygen vented to space [5].
For the first four landings (Apollo 11 to 14) the backpack supported moonwalks of up to 4 hours. For Apollo 15 to 17 it was upgraded with more oxygen, lithium hydroxide, cooling water and battery power, doubling the limit to 8 hours [5]. The modern ISS backpack does the same jobs and supports about 8.5 hours, including a 30 minute reserve [4]. ISS suits also carry SAFER, a small jet pack an astronaut could use to fly back if they became separated from the station [1].
How much does a space suit weigh?
The Apollo lunar suit with its backpack weighed about 81.6 kg (180 lb) on Earth, which matches the figure on the diagram. In the Moon’s weaker gravity that felt like about 13.6 kg (30 lb) [3]. Other figures you will see depend on what is counted: specification tables give a total of about 91 kg for the full Apollo 7 to 14 suit system and about 96 kg for the longer missions [3]. The backpack on its own weighed about 38 kg (84 lb) on Earth [5].
The ISS suit is heavier, at about 115 kg (254 lb) in total, but in orbit it is weightless [4].
Who made the Apollo space suit?
The pressure garment was made by ILC (the International Latex Corporation, now ILC Dover), and the backpack by Hamilton Standard [3]. The International Latex Corporation, later known as Playtex, was best known for women’s underwear, and its Apollo suits were made by a team of skilled seamstresses [3][6]. The Smithsonian, which holds Neil Armstrong’s Apollo 11 suit, lists its materials as beta cloth, rubber, nylon and plastic, with aluminium connectors and a brass zip [2].
The next generation of space suits
NASA’s suits for the Artemis Moon missions are being built by Axiom Space. Its design, the AxEMU, is meant to handle the temperature, dust and radiation expected on Artemis moonwalks, and it uses the same basic parts: cooling garment, pressure garment, outer layers, helmet and backpack [7]. Axiom worked with Prada on the outer cover and the cooling garment [7].
Questions about space suits
What are the main components of a space suit?
A cooling garment, a pressure garment, protective outer layers, a helmet and visor, gloves, boots and a life support backpack. On the ISS suit the chest is a rigid Hard Upper Torso that the backpack attaches to [1][4].
How many layers does a space suit have?
It depends on the suit. On the Apollo A7L the outer thermal and micrometeoroid cover alone had 13 layers, on top of the pressure bladder and the three layer cooling garment [3].
What is inside a space suit backpack?
Oxygen tanks, a carbon dioxide scrubber, a fan, a water tank and pump for cooling, a sublimator, batteries and a radio, plus an emergency oxygen supply [5].
How do astronauts breathe in a space suit?
The backpack supplies oxygen and circulates it through the suit, removing carbon dioxide, moisture and odours before the gas is breathed again [5].
How hot or cold can a space suit handle?
Spacewalk suits are built for conditions in Earth orbit of about minus 157°C (minus 250°F) to about 121°C (250°F) [1].
Sources
- NASA, What Is a Spacesuit?
- Smithsonian National Air and Space Museum, Pressure Suit, A7-L, Armstrong, Apollo 11, Flown.
- Wikipedia, Apollo/Skylab A7L spacesuit.
- Wikipedia, Extravehicular Mobility Unit.
- Wikipedia, Primary life support system.
- Wikipedia, ILC Dover.
- Wikipedia, Axiom Extravehicular Mobility Unit.
Last reviewed 3 November 2026
