Over the last 20 years, new technologies developed by NASA resulted in a new spacesuit prototype, xEMU (Exploration Extravehicular Mobility Unit). It is from this research that the future AxEMU spacesuits for the Artemis III mission emerged, the aim of which is to relaunch lunar exploration by humanity.
The new combinations are in development at Axiom Space (under contract with NASA). This company created a surprise by announcing, in October 2023, a partnership with the famous Italian fashion house Prada.
A spacesuit is like a spaceship… designed for a single user and capable of movement, with two main components: the pressurized suit and the life support system.
The pressurized garment, which can have up to sixteen layers, fits the contours of the body, protects it and allows a certain freedom of movement.
In space, astronauts face a hostile environment where heat is transmitted primarily via radiation. The outer layers of the suits are exposed to extreme temperatures (between +120°C and -180°C) depending on whether the astronaut receives solar radiation or faces outer space, the temperature of which is – 270°C. To thermally insulate the astronauts from the outside, a system is used consisting of many layers of aluminized mylar.
In addition, the outer layer, made of “Ortho-Fabric”, must not only protect the astronaut against various dangerssuch as ionizing radiation, ultraviolet rays, plasma and micrometeorites, but also play a key role in the absorption and emission of radiation.
Its thermo-optical properties are essential for keeping astronauts at the right temperature. The suits’ characteristic white color reflects much of the direct solar radiation and that of the lunar surface (albedo) while emitting a large amount of radiation.
Lunar dust, the biggest problem
A big challenge is the abrasive dust from the lunar surface, which must not penetrate the suit. In addition, this dust, which constitutes the lunar regolith (or soil), carries electrostatic charges. These charges cause dust to adhere to the surface of the suit, which considerably complicates even the smallest task for astronauts.
Gene Cernan, the commander of the Apollo 17 mission, discussed the challenges of lunar dust when speaking about his experiment on the Moon :
“I think we can overcome all physiological, physical and mechanical problems except dust. », Gene Cernan, commander of the Apollo 17 mission.
This is why current xEMUs integrate a electrodynamic dust shield. This system exploits these electrostatic charges to dislodge lunar dust from the outer surfaces of the suits.
Spacesuits sweat too
If we completely isolate the astronaut from the external environment, we are faced with a considerable challenge: the body itself radiates heat through metabolism, generating between 200 and 400 watts depending on the activity physical, which should lead to an increase in temperature inside the suit. To avoid this problem, under the pressurized layer, the liquid cooling and ventilation garment (LCVG) is in direct contact with the astronaut’s skin.
In the 1970s, it was realized that airflow cooling was not sufficient for spacesuits and the closed-loop liquid cooling of the LCVG began to be used.
In this system, water circulates around the body using a pump and absorbs heat. It is then directed to a heat exchanger in the life support system. In this device, the water in a tank is exposed to vacuum and freezes, which reduces the temperature of the cooling circuit: when the ice in the tank absorbs the heat of the fluid in the cooling circuit, it is sublimated, c that is to say, it goes directly into the gaseous state. This vapor is released into space through a porous system.
Despite the effectiveness of this type of “sublimator”, the quantity of water it consumes is too high (nearly half a liter per hour), which current xEMU suits cannot handle.
It was therefore replaced by a system called SWME, where a membrane composed of polypropylene fibers with very small diameter pores is exposed to a vacuum. Liquid water from the cooling system cannot pass through the membrane (and therefore cannot exit the system. On the other hand, steam can pass through the pores of the membrane: the pressure drop in the SWME causes evaporation of part of the water, which is thus released into space – the system thus evacuates a large part of the heat produced by the astronaut’s metabolism.
CO₂ and water filters that regenerate
One of the fundamental requirements of spacesuits is the need to eliminate CO2 and water vapor from the inside. Excess humidity, in addition to being uncomfortable for astronauts’ activities, can lead to condensation inside the suit.
Older EMU suits used a silver oxide filter that had to be replaced after a few hours of use. The new xEMU suits will incorporate a significant improvement: the system “Rapid Cycle Amine”. In this technology, the CO2 and the H2O are absorbed by an absorbent layer. While this first layer is exposed to vacuum, allowing molecules to be released into space (desorption), a second layer continues the absorption process.
This self-regeneration cycle increases the autonomy of the suits.
What effect does emptiness have on us?
One of the challenges we face when working in space is vacuum. When air pressure decreases, the amount of oxygen becomes insufficient for astronauts to survive.
One of the problems is that this low pressure lowers the boiling point of water. At an altitude of more than 19 kilometers, at a pressure of 3.5 kilopascals, water begins to boil at room temperature… which poses a serious problem because the human body contains more than 60% water. Thus, this altitude is known as the “Armstrong limit”, beyond which humans would not survive more than a few minutes.
Without protection, water from our body would escape through the pores of the skin. As it evaporates, it would absorb internal heat, which would cause the nose and mouth to gradually freeze. Even if the rigidity of our skin and the continuous pumping of our circulatory system kept the blood from boiling, it would only take about a minute to cause cardiac arrest.
It goes without saying that spacesuits must be pressurized, but too high a pressure would hamper the astronaut’s mobility. For extravehicular activities, spacesuits are therefore generally pressurized to 30 kilopascals (i.e. one third of the ambient pressure on Earth), with pure oxygen.
One of the main improvements of the xEMU suits is their variable pressurization system, which reduces the time needed for astronauts to adapt their breathing to this relatively low pressure generated by pure oxygen. If the transition is too abrupt, the nitrogen contained in the blood can form fatal bubbles, just as happens to divers when they return to the surface, or like CO bubbles.2 which form when opening a soft drink.
Spacesuits are relatively new technologies – with barely 60 years of history – and the only shield against the most adverse conditions humans face in space. They must also be our allies in the exploration of the Moon and other planets in the solar system. We are perhaps not so far from what, just yesterday, was science fiction.
Translated from Spanish by Jean-Louis Duchamp for FastForWord.