Extravehicular Mobility Unit
For more than four decades, astronauts conducting spacewalks outside the International Space Station (ISS) have relied on a single, proven design: the Extravehicular Mobility Unit, or EMU. This suit, a veteran of the Space Shuttle program, is a marvel of engineering. It’s also a product of 1970s technology. As humanity prepares to return to the Moon and establish a commercial economy in low Earth orbit (LEO), the need for a new generation of spacesuits has become undeniable.
The old model, where NASA designed, built, and owned every piece of hardware, is shifting. In its place, a new commercial paradigm is rising. NASA is now seeking to be a customer, purchasing services – including spacewalks – from private companies. This strategy is intended to foster innovation, drive down costs, and create a sustainable space infrastructure independent of government-only funding.
Entering this new market is Axiom Space, a company building the world’s first commercial space station. To service that station and to support NASA’s ambitious lunar goals, Axiom Space is developing a state-of-the-art spacesuit. Known as the Axiom Extravehicular Mobility Unit (AxEMU), this suit represents a significant leap forward in design, capability, and versatility. It’s not just an upgrade; it’s a fundamental reimagining of how humans will work, explore, and live outside the confines of a spacecraft. This article explores the design, purpose, and technology of the AxEMU, the spacesuit intended to take astronauts to the lunar surface for the Artemis program and beyond.
The Case for a New Suit
The existing EMU spacesuit is one of the most reliable systems ever flown by NASA. Astronauts have used it to build the International Space Station, repair the Hubble Space Telescope, and perform thousands of hours of extravehicular activity (EVA). But its age presents serious challenges.
The EMU was designed decades ago, and its inventory is limited. The suits currently on the ISS are refurbished and pieced together from components, many of which have been flying for longer than the astronauts wearing them have been alive. This creates a significant maintenance and logistics burden. Refurbishing a suit on the ground is a costly and time-consuming process, taking months or even years.
A primary limitation of the EMU is its sizing. The suit is built around a Hard Upper Torso (HUT) that comes in a few fixed sizes. This means not all astronauts can be comfortably, or even safely, accommodated for a spacewalk. This lack of modularity has led to scheduling issues on the ISS when suits in the correct size weren’t available.
Furthermore, the EMU was designed purely for microgravity. An astronaut in an EMU primarily uses their hands to translate along handrails, with their legs and feet used mostly to anchor themselves to workstations. The suit isn’t designed for walking, bending, or kneeling. Using it on a planetary surface like the Moon would be impractical and dangerous. The stiff, high-pressure design severely restricts lower-body mobility, which is why the Apollo astronauts developed their famous “bunny hop.”
As NASA set its sights on the Artemis program and the commercial space industry began planning private space stations, it was clear that a new solution was needed. The requirements for a 21st-century spacesuit are demanding: it must be more mobile, more modular, easier to maintain, and adaptable to different environments, from the vacuum of orbit to the dusty plains of the lunar south pole.
Axiom Space and the Commercial Model
Axiom Space was founded in 2016 with the goal of building a commercial successor to the International Space Station. The company’s business plan involves launching its own modules, beginning with attaching them to the ISS before separating to become a free-flying independent station, known as Axiom Station. This station will serve a mix of clients, including government astronauts from various nations, private researchers, and space tourists.
To operate this station, Axiom Space needs its own infrastructure, including the ability to conduct spacewalks. This internal need positioned the company perfectly to answer NASA’s call for commercial spacesuit services.
In 2022, NASA awarded two contracts under the Exploration Extravehicular Activity Services (xEVAS) program. This was a major policy shift. Instead of paying a contractor to build suits that NASA would then own and manage, the xEVAS contract allows NASA to purchase spacewalking services from qualified providers. Axiom Space was one of the two companies selected, along with Collins Aerospace.
This “Spacesuit as a Service” model places the responsibility for design, development, certification, and maintenance squarely on the private company. Axiom Space isn’t just delivering a product; it’s providing an end-to-end service that includes the suit, all the necessary support equipment, and the training for astronauts to use it. In return, NASA gets access to cutting-edge technology without the massive upfront development cost and long-term logistics burden. This competitive, service-based approach is expected to lower costs and accelerate timelines, allowing NASA to focus on its core exploration mission.
Under this contract, Axiom Space was tasked with developing a suit that could be used both on the ISS and for the Artemis III mission, which is planned to be the first human lunar landing since 1972.
Anatomy of the AxEMU
The Axiom AxEMU spacesuit is a complex, multi-layered system designed to function as a self-contained, human-shaped spacecraft. It must protect the astronaut from the vacuum of space, shield them from extreme temperatures and micrometeoroids, provide breathable air, and allow enough mobility to perform useful work.
While the suit’s architecture builds on the lessons learned from the EMU and Apollo suits, it incorporates modern materials, manufacturing techniques, and a design philosophy centered on mobility and modularity.
The Pressure Garment System
The main body of the suit is the Pressure Garment System (PGS). This is the part that holds in the oxygen and provides the correct pressure for the astronaut to survive. A spacesuit is essentially a personalized balloon. The challenge is that when you pressurize a balloon, it becomes very stiff. Every movement requires bending the stiff, pressurized fabric, which is incredibly fatiguing.
The AxEMU’s primary innovation is its enhanced mobility. The suit is designed to operate at a pressure similar to the EMU (around 4.3 psi), but it achieves greater flexibility through advanced joint design. The suit incorporates carefully placed bearings and “constant volume” joints. A constant volume joint, like in the elbows and knees, is designed so that bending it doesn’t significantly change the internal volume of the suit. This means the astronaut isn’t fighting against the pressure of the air inside, making movement far less strenuous.
The suit’s arms and legs are a significant departure from the EMU. They are designed to provide a much wider range of motion, especially in the shoulders, hips, and knees. This is a direct requirement for the lunar mission, where astronauts will need to walk, bend over to pick up rocks, kneel, and get up if they fall. The AxEMU allows for walking, crouching, and traversing uneven terrain in a way the old EMU simply cannot.
Sizing and Modularity
Addressing the sizing limitations of the EMU was a key design driver for the AxEMU. Instead of just a few fixed-size upper torsos, the AxEMU is built to be highly modular. It features components that can be mixed and matched to fit a much wider range of astronaut body types, from the 5th percentile female to the 95th percentile male.
This is achieved through a combination of adjustable components and a wider variety of part sizes. This modularity not only improves safety and comfort but also streamlines logistics. It’s easier to fit a diverse crew and to have the right-sized parts available when needed, whether on the ISS or at a base on the Moon.
The Helmet and Display
The AxEMU helmet provides a wide field of view, which is essential for situational awareness. Integrated into the helmet system are high-definition video cameras to broadcast the astronaut’s point of view back to Earthand a sophisticated lighting system. The old EMU requires astronauts to attach external lights and cameras, adding to their pre-EVA setup time. The AxEMU integrates these systems directly.
Perhaps the most futuristic element is the information display. While details are evolving, the system is expected to feature a head-up display (HUD) projected inside the visor. This would give the astronaut real-time data on their suit’s status – oxygen levels, battery power, carbon dioxide readings – as well as procedural checklists and navigation cues. This is a massive improvement over the EMU, which uses a chest-mounted display with text and codes that the astronaut must look down to read.
Gloves: The Unsung Challenge
Spacesuit gloves are widely considered the single most difficult part of the suit to design. The human hand is a masterpiece of dexterity, and replicating any fraction of that in a pressurized, protective glove is an enormous engineering challenge. The gloves must protect against the vacuum and temperatures that can swing hundreds of degrees, yet they must be flexible enough for an astronaut to grip a tool, flip a switch, or pick up a small object.
EMU gloves are notoriously tough on astronauts’ hands. The combination of stiffness and the need to constantly grip against pressure can cause blisters, abrasions, and even damaged fingernails after a long spacewalk.
The AxEMU gloves are a major area of focus. Axiom Space is leveraging advanced materials and new fabrication techniques to create gloves that offer greater dexterity with less fatigue. This includes using 3D scanning to custom-fit gloves to an astronaut’s hands and exploring new joint patterns and materials that bend more easily under pressure. For lunar missions, the gloves will also have a tough outer layer to protect against the sharp, abrasive lunar regolith.
The Portable Life Support System (PLSS)
If the pressure garment is the body, the “backpack” is the heart and lungs. The Portable Life Support System (PLSS) contains all the equipment needed to keep the astronaut alive. The AxEMU’s PLSS is a highly integrated and miniaturized system.
It performs several functions:
- Oxygen: It provides 100% oxygen for the astronaut to breathe and maintains the suit’s pressure.
- CO2 Removal: It actively scrubs the carbon dioxide (CO2) that the astronaut exhales. A buildup of CO2 is toxic and one of the greatest dangers during an EVA.
- Thermal Control: The suit’s interior gets very hot from the astronaut’s body heat. The PLSS circulates cool water through a network of tubes in an undergarment worn by the astronaut. This water absorbs the body heat. The hot water then flows back to the PLSS, where the heat is rejected into space through a process called sublimation.
- Power and Communications: The PLSS houses the batteries that power the entire suit – its computers, fans, pumps, lights, and radios – as well as the communication system that links the astronaut to their crewmates, the spacecraft, and Mission Control.
The AxEMU PLSS is designed to be more efficient and easier to service than the EMU’s backpack, incorporating modern electronics and more robust systems to support longer and more complex spacewalks.
Developing and Testing the Future
Creating a new, human-rated spacesuit from scratch is one of the most difficult tasks in aerospace engineering. The AxEMU has been undergoing a rapid and intensive development and testing campaign to prepare it for its first flights.
When Axiom Space unveiled its first AxEMU prototype in March 2023, it captured public attention with its sleek, dark design. This outer cover was just a protective layer to conceal the suit’s proprietary technology. The final, operational suits will be white.
A white outer layer is essential for thermal control. In direct sunlight in space or on the Moon, a dark surface would absorb too much heat. A white surface reflects the vast majority of solar radiation, helping to keep the astronaut cool. This outer layer, known as the Thermal Micrometeoroid Garment (TMG), is composed of multiple layers of advanced fabrics like Kevlar, Gore-Tex, and Mylar to insulate the astronaut and protect them from impacts by tiny, high-speed space debris.
The suit’s testing regimen is rigorous. Engineers and test subjects wear the suit in vacuum chambers to ensure it holds pressure and that its life support systems function correctly in a vacuum.
The most visible form of testing takes place at NASA’s Neutral Buoyancy Laboratory (NBL) in Houston, Texas. The NBL is a massive swimming pool, large enough to hold full-scale mockups of the International Space Station. By carefully weighting the astronaut and the suit, engineers can simulate the weightlessness of microgravity. Here, astronauts practice moving, using tools, and rehearsing emergency procedures, providing direct feedback to the suit’s designers. The AxEMU’s performance in the NBL is a key part of its certification for use on the ISS.
The Artemis Challenge: From Orbit to the Moon
The AxEMU is not just one suit; it’s a platform. It’s being designed as a base architecture that can be adapted for two very different environments. The first version is intended for microgravity EVAs at the ISS and Axiom Station. The second, more complex version, is the lunar suit for the Artemis program.
NASA selected the AxEMU to be the suit worn by the Artemis III astronauts, who will be the first to walk on the Moon in the 21st century. This mission presents a set of challenges far different from those in low Earth orbit.
The Gravity Problem
The Moon has one-sixth the gravity of Earth. This is not zero gravity, so the suit must be able to support its own weight and the astronaut’s weight, while allowing for natural, fluid movement. The EMU, designed for weightlessness, is not built to handle this.
The AxEMU’s lunar variant must have a robust lower-body system with flexible joints at the hips, knees, and ankles. Astronauts won’t be floating; they’ll be walking, climbing slopes, bending to collect geological samples, and setting up equipment. The suit’s center of gravity must be carefully managed to prevent astronauts from toppling over, and if they do fall, the suit must give them the mobility to get back up on their own – a feat that was extremely difficult for Apollo astronauts.
The lunar boots are also completely different. In microgravity, boots are just covers with simple foot restraints. On the Moon, they need flexible, high-traction soles, similar to hiking boots, to grip the loose lunar soil.
The Dust Problem
The single greatest environmental threat on the Moon is not radiation or temperature; it’s dust. Lunar regolith is not like sand on Earth. It’s the product of billions of years of micrometeoroid impacts, which have shattered the rock into tiny, razor-sharp particles. It’s electrostatically charged by the solar wind, so it clings to everything.
This dust is incredibly abrasive. It can wear through fabric, clog mechanisms, and destroy seals. The Apollo astronauts found it to be a major nuisance; it got into every part of their lunar module and spacesuits. For a short, three-day stay, it was manageable. For the sustained presence planned for Artemis, it’s a mission-critical engineering problem.
The AxEMU’s lunar design must incorporate advanced dust-mitigation strategies. This includes using special materials that don’t hold a static charge, designing seals and bearings that are impervious to the fine powder, and developing procedures for cleaning the suits before astronauts re-enter their lander. The Apollo suits were essentially disposable; they were worn for one mission and discarded. The AxEMU must be reusable for multiple EVAs on a single mission and for many missions over its lifespan.
The Thermal Problem
An astronaut on the ISS experiences a “day” and “night” every 90 minutes, with temperatures swinging rapidly. The suit’s cooling system is designed for this cycle.
On the Moon, a day lasts for 14 Earth days, followed by 14 days of night. In direct sunlight, the lunar surface can reach 120°C (250°F). In shadow, it plummets to -130°C (-208°F). The Artemis missions are targeting the lunar south pole, in part because there are areas of near-permanent sunlight for power, but also areas of permanent shadow that are thought to contain water ice.
An astronaut on a lunar EVA could walk from a brightly lit area into a permanently shadowed crater, experiencing a thermal swing of hundreds of degrees. The AxEMU’s PLSS must be far more powerful and responsive than the EMU’s. It needs to be able to dump massive amounts of heat when the astronaut is working hard in the sun, yet protect them from a hypothermia-inducing cold soak the moment they step into shadow. This requires a highly advanced thermal control system, likely with upgraded radiators and potentially new methods of heat management.
Axiom Space Is the Sole Service Provider
The AxEMU is being developed under NASA’s xEVAS contract, which was originally awarded in 2022 to two providers: Axiom Space (for the AxEMU) and Collins Aerospace (partnered with Oceaneering and ILC Dover, the company that built the Apollo and current EMU suits). This dual-award approach was a deliberate NASA strategy to promote competition, innovation, and risk reduction. However, in June 2024, NASA and Collins Aerospace mutually agreed to descope (remove) Collins’ task orders due to development challenges, leaving Axiom Space as the sole active provider for next-generation spacesuits for both the International Space Station and lunar surface operations. As of November 2025, the AxEMU remains on track for certification and use in future Artemis missions.
NASA won’t be Axiom’s only customer. Axiom Space is building these suits for its own private astronauts who will be working on Axiom Station. The company could also sell or lease suit services to other space agencies, private research firms, or even in-space manufacturing and media companies that may one day operate in LEO. This diversified customer base creates a stable commercial market, ensuring that spacesuit technology will continue to advance, driven by the needs of multiple users, not just a single government agency.
Summary
The Axiom AxEMU spacesuit is far more than just a new piece of clothing. It is a cornerstone of the next chapter in human space exploration. It represents a pivot from a government-owned and-operated model to a commercial, service-based economy in space.
Born from the need to replace the venerable but aging EMU, the AxEMU is designed for a new generation of astronauts and a new set of destinations. Its modular design promises to fit a wider range of people. Its advanced joints and bearings offer a level of mobility that will be essential for meaningful work on the lunar surface. Its integrated digital displays, lighting, and cameras provides astronauts with unprecedented awareness and capability.
The development of this suit is a significant engineering undertaking, requiring solutions to the classic challenges of pressure and mobility, as well as the new and harsh problems posed by lLunar regolith and extreme temperatures. As the suit selected for the historic Artemis III mission, the AxEMU is on a path to be the first suit to carry humans on the Moon in over half a century.
By providing “Spacesuit as a Service,” Axiom Space is not only supporting NASA’s exploration goals but also building the infrastructure for its own commercial space station and the broader LEO economy. The AxEMU, and its competitor from Collins Aerospace, are the first examples of what will likely become a competitive market for the most complex human-rated hardware, ensuring that as humanity’s reach extends, the technology to support it will be ready.
