Table of Contents

Why Wear a Spacesuit?

The need to breathe is probably the most obvious reason that an astronaut needs to wear a spacesuit. But did you ever consider that a spacesuit is like a spacecraft only smaller? Like a spacecraft, the suit offers a stable environment to work in and protection from the harsh realities of space!

Breathing Space: How Oxygen Moves in the Suit

On Earth, humans breathe by taking in oxygen from the air and exhaling carbon dioxide as waste from their bodies. In space, the Primary Life Support System (PLSS) on the astronaut’s back has to perform the same role in space: it has to provide oxygen and get rid of carbon dioxide.

Oxygen is a gas that’s moved throughout the suit using a closed-loop system—a system that measures and monitors how oxygen is being used, conserves and recycles oxygen, and if necessary, activates the secondary oxygen pack when oxygen pressure drops to a certain level.

Oxygen travels from the PLSS through a number of ducts built into the Hard Upper Torso and gets warmed up before getting passed up into the back of the helmet--this prevents the visor from fogging up.

The gas then travels from the back of the head, over the head, and down the front so that it can pick up the carbon dioxide and humidity that’s created as the astronaut breathes. From there, it travels down to the rest of the suit and collects heat, humidity from sweat, and any trace contaminants as it gets drawn towards the ducts built into the Liquid Cooling-and-Ventilation Garment (LCVG).

A fan sucks the "dirty" oxygen back into the PLSS to draw it through a Contaminant Control Cartridge. This cartridge filters out carbon dioxide and contaminants, while a heat exchanger and sublimator remove the humidity from the gas. The heat exchanger trades warm air being removed from the suit with cooler air coming into the suit. The plates in the sublimator freezes the water into ice. This ice is converted directly into water vapor that is released into space. This process removes heat from the water and so any water returning from the sublimator is very cold. This cold water mixes with any warm water that did not pass through the sublimator and then it travels back into the LCVG.

The remaining gas goes through a carbon dioxide sensor before it travels through the same loop again. More oxygen gets added from the supply in the PLSS as required.

Should the fan ever stop working, the Secondary Oxygen Pack gets activated: the closed loop is broken and an open loop is started. The oxygen will still follow the same path from the PLSS, but before it reaches the Contaminant Control Cartridge, it will get dumped into space.

Feeling the Pressure

On Earth, pressure is exerted in all directions. If there were no pressure, the air in our lungs would rush out. The gases in our body fluids would expand and boil off. That would mean game over!

No pressure is exerted in space because it is a vacuum. A vacuum can be described as the absence of matter. (In space, the gravitational attraction between planets and stars is low which means that that there are large gaps of nothingness between them. Any gas molecules that might be found floating between the planets and stars have such a low density that they’re considered of as non-existent.)

So, to ensure the astronaut’s survival in space, the suit needs to be pressurized. The suit’s pressure operates only at one-third of the pressure we experience on the surface of the Earth. That’s because the lack of pressure in space makes the suit act like a rigid balloon. Keeping the pressure as low as possible makes it easier for the astronauts to bend and move in the suit as they perform their tasks.

Therefore, the spacesuit is necessary in providing an environment that supplies oxygen for breathing and maintains pressure around the body.

Not Your Regular Coat of Armour

The suit can also be thought of as a coat of armour—only not as difficult to move in! The suit consists of a seven-layer thermal micrometeoroid garment that protects the astronaut from micrometeoroids. Even though the prefix "micro" is used, don’t be fooled! These little bits of rock travel at such high velocities that they can pierce through human skin and thin sheets of metal!

It also protects the wearer from the extremely hot and cold temperatures in space. On Earth, we have the atmosphere to act as a filter for the Sun’s rays. In space, there is no filter. What does this mean for the astronauts? If they are facing the Sun, they are exposed to broiling temperatures well over 100 °C—that’s hot! If they are working in the dark, the temperature can drop below -100°C.