New space suits will take us to the moon

Over the past 20 years, At NASA A new spacesuit prototype called xEMU (Exploration Extravehicular Mobility Unit) has developed new technologies. xEMU was the starting point for designing the AxEMU spacesuits for the Artemis III mission, the mission of which was to return humans to the lunar surface.

The company is developing these new clothes Axiom Space (under contract with NASA), it announced in October last year and surprised Cooperation agreement With famous Italian fashion brand Prada.

The AxEMU spacesuit is provided by Axiom Space. Axiom Space

Multi-layered skin

A spacesuit resembles a spaceship designed for a user and equipped with mobility. The structure of a spacesuit can be divided into two main components: the pressure garment and the life support system.

A pressure suit with up to 16 layers, part of a human-shaped spacesuit, protects the body and allows movement.

In space, astronauts are exposed to a very hostile environment where heat is dissipated mainly by radiation. The outer layers of the suits reach extremely extreme temperatures (+120ºC and -180 ºC) when the astronaut receives solar radiation or he is only exposed to deep space, with a temperature of -270 ºC. A system is in place to thermally insulate the astronauts from outside Multiple layers A substance known as Aluminum mylar.

Also, the ortho-fabricated outer layer should only protect the astronaut. Various risksIonizing radiation plays a fundamental role, as do ultraviolet radiation, plasma, and meteorites, but also by absorbing and emitting radiation.

Its thermo-optical properties are important to keep astronauts at an adequate temperature. The characteristic white color of the soot reflects much of the direct solar radiation and they emit a large amount of radiation at the same time as it reaches it from the lunar surface (albedo).

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Moon dust, the biggest problem

On the lunar surface, a significant challenge is added: abrasive dust that should not enter the suit. In addition, the lunar regolith contains electrical charges that cling to the surface of the suit, making any task very difficult.

Astronaut Harrison Schmidt traveled in space during the Apollo 17 mission. NASA, CC BY

Apollo 17 commander Gene Cernan expressed difficulty reflecting when lunar dust spoke of itself. Experience on the moon: “Besides dust, I think we can deal with physiological or physical or mechanical problems.”

Current xEMUs are a Electrodynamic dust shield. The system uses these electrostatic charges to dislodge lunar dust from the outer surface of the spacesuit.

Space suits are also sweaty

If we completely isolate the astronaut from the external environment, we face a considerable challenge: the organism itself dissipates heat through metabolism, generating between 200 and 400 W depending on physical activity. This will increase the temperature inside the suit. To avoid this problem, there is a ventilated and liquid cooling suit below the pressure-maintaining layer and in contact with the astronaut's skin. (LCVG).

In the 1970s air cooling in spacesuits was found to be insufficient and LCVG was used for liquid cooling through a closed circuit.

In this system, pump-driven water circulates around the body, absorbing heat. It then goes to a heat exchanger located in the life support system. In this device, water from a tank is exposed to a vacuum and freezes, lowering the temperature of the cooling circuit. When snow absorbs heat from it, sublimation occurs, which turns directly into water vapor and is released into space through a porous structure.

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Despite the efficiency of this sublimator, the amount of water it consumes is very high (almost half a liter per hour), something that cannot be afforded in current xEMU cases. For this reason, it is replaced by a system called a sublimator SWME, based on the use of a vacuum-exposed membrane composed of polypropylene fibers with small pores. This membrane prevents liquid water from the cooling system from passing through it, while allowing steam to pass through. The pressure drop in the SWME causes a portion of the water to evaporate and release into space, absorbing much of the metabolic heat of the circulation.

How do spacesuit cooling systems work? Source: NASA Johnson.

CO₂ and water regeneration filters

A basic requirement for spacesuits is to remove CO₂ and water vapor from the interior. High humidity is not comfortable for astronauts' operations and can cause water condensation inside the suit.

Unlike older EMU suits that used a silver oxide filter that could be replaced after a certain number of hours of use, the xEMU suits have a significant improvement over the system. “Rapid Cycle Amine”. Once the CO₂ and H₂O are absorbed by the absorbent bed, it is exposed to a vacuum, allowing the molecules to be released into space while another bed continues the absorption process. This self-healing cycle increases the spacesuits' autonomy.

How does emptiness affect us?

The challenge we face when we have to work in space is “emptiness”. As the pressure in the air decreases, the amount of oxygen is insufficient for the survival of the astronauts.

A stress-related problem It is related to the boiling point of water. At a pressure of 3.5 kPa, above an altitude of 19 km (called the Armstrong limit), water begins to boil at room temperature. Since approximately 60% of our body is made up of water, a serious problem develops under these conditions.

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The water in our body starts to leak out through the pores of our skin. During evaporation, the water absorbs heat from our body and gradually freezes the nose and mouth. Although the stiffness of our skin and the continuous pumping of our circulatory system prevent the blood from boiling, unfortunately, it only takes a minute for the heart to stop.

It is clear that spacesuits must be pressurized, even if excess pressure can impede the astronaut's movement. For this reason, in extravehicular operations, spacesuits are usually pressurized with pure oxygen up to 30 kPa (one third of ambient pressure).

One of the notable improvements in xEMU suites is a Variable pressure system This reduces the amount of time astronauts have to replace their breathing with pure oxygen at low pressure. If this is done suddenly, the nitrogen in the blood can form dangerous bubbles for astronauts, similar to what happens to divers when exposed, or CO₂ bubbles form when opening a soft drink.

In its 60-year history, spacesuits have proven to be our shield against the harshest conditions we've encountered beyond Earth, and promise to be our partner in exploring not just the Moon, but the rest of the planet. . It's possible that we weren't that far removed from science fiction until recently.

David Gonzalez-BarsenaAssistant Professor at ETSIAE's Department of Fluid Dynamics and Space Propulsion and Researcher at the “Ignacio da Riva” University Institute of Microgravity, Polytechnic University of Madrid (UPM)

This article was originally published Conversation. to read Original.

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