How Space Suits Work

Modern Space Suit: EMU

Astronaut in LCVG preparing for a spacewalk
Photo courtesy NASA

While early space suits were made entirely of soft fabrics, today's Extravehicular Mobility Unit (EMU) has a combination of soft and hard components to provide support, mobility and comfort. The suit itself has 13 layers of material, including an inner cooling garment (two layers), pressure garment (two layers), thermal micrometeoroid garment (eight layers) and outer cover (one layer). The materials used include:

  • Nylon tricot
  • Spandex
  • Urethane-coated Nylon
  • Dacron
  • Neoprene-coated Nylon
  • Mylar
  • Gortex
  • Kevlar (material in bullet-proof vests)
  • Nomex

All of the layers are sewn and cemented together to form the suit. In contrast to early space suits, which were individually tailored for each astronaut, the EMU has component pieces of varying sizes that can be put together to fit any given astronaut.


The EMU consists of the following parts:

  • Maximum Absorption Garment (MAG) - collects urine produced by the astronaut
  • Liquid Cooling and Ventilation Garment (LCVG) - removes excess body heat produced by the astronaut during spacewalks
  • EMU Electrical Harness (EEH) - provides connections for communications and bio-instruments
  • Communications Carrier Assembly (CCA) - contains microphones and earphones for communications
  • Lower Torso Assembly (LTA) - lower half of the EMU including pants, knee and ankle joints, boots and lower waist
  • Hard Upper Torso (HUT) - hard fiberglass shell that supports several structures including the arms, torso, helmet, life-support backpack and control module
  • Arms
  • Gloves - outer and inner gloves
  • Helmet
  • Extravehicular Visor Assembly (EVA) - protects the astronaut from bright sunlight
  • In-suit Drink Bag (IDB) - provides drinking water for the astronaut during the spacewalk
  • Primary Life Support Subsystem (PLSS) - provides oxygen, power, carbon dioxide removal, cooling water, radio equipment and warning system
  • Secondary Oxygen Pack (SOP) - provides emergency oxygen supply
  • Display and Control Module (DCM) - displays and controls to run the PLSS

Maximum Absorption Garment (MAG)

Spacewalking astronauts can spend up to seven hours spacewalking. During that time, their bodies produce urine. Because it takes too much time to pressurize and depressurize both the space suits and the airlocks/spacecraft, astronauts cannot simply go inside the spacecraft and use the toilet to relieve themselves. Therefore, each spacewalking astronaut wears a large, absorbant diaper to collect urine and feces while in the space suit. The astronaut disposes the MAG when the spacewalk is over.

Liquid Cooling and Ventilation Garment (LCVG)

LCVG is a set of Nylon tricot and spandex "long underwear" that is laced with thin plastic tubes. Cool water flows through these tubes to remove the heat produced by the astronaut. The cooling water comes from the space suit's backpack unit or from the spacecraft through an umbilical cord (used in the airlock while preparing for the spacewalk).

EMU Electrical Harness (EEH)

This is a set of communications wires and bioinstruments that is worn by the astronaut inside the suit. It provides connections to the radio and bioinstruments in the suit's backpack. It allows for communication and for monitoring of the astronaut's vital signs (respiration rate, heart rate, temperature, etc.).

Communications Carrier Assembly (CCA)

The CCA is a fabric cap worn by the astronaut. It contains microphones and speakers for use with the radio. It allows hands-free radio communications within the suit.

Lower Torso Assembly (LTA)

The LTA is a one-piece unit that contains the lower half of the EMU, including pants, knee and ankle joints, boots and lower waist. It is fitted to the upper half of the EMU by a metal connect ring. The LTA has loops to tether tools so that they do not float away in space.