A Human-Shaped Spacecraft: The Materials, History, and Technology of the Spacesuit

The Personal Spacecraft

A spacesuit is not merely a piece of clothing. It is, in the most literal sense, the world’s smallest and most personal spacecraft. When an astronaut performs an extravehicular activity (EVA), or spacewalk, they are not just wearing a suit; they are inhabiting a meticulously engineered vehicle shaped in their own image. This garment must perform all the life-sustaining functions of a multi-ton orbiter but be flexible enough to allow a human being to work, explore, and conduct science. It is a self-contained world, a portable bubble of Earth’s environment designed to protect its fragile occupant from the utterly lethal vacuum of space.

The challenges that every spacesuit must overcome are absolute and unforgiving. Without an atmosphere, space is a perfect vacuum. This absence of pressure would cause a person’s bodily fluids to boil away in seconds, a fatal condition known as ebullism. The suit must therefore provide a stable, pressurized atmosphere of breathable oxygen while actively removing the carbon dioxide the astronaut exhales. It must also shield its occupant from a constant barrage of threats. Temperatures in direct sunlight can soar to over 121 °C (250 °F), while in shadow they can plunge to below -157 °C (-250 °F). The suit must insulate the astronaut from these violent swings. It must also provide protection from the invisible threat of solar radiation and the physical danger of micrometeoroids – tiny particles of rock and metal traveling many times faster than a bullet, capable of puncturing a lesser garment with catastrophic results.

Beyond mere survival, a spacesuit must enable work. It must allow the astronaut inside to move their arms, bend their knees, and flex their fingers. This fight for mobility against the natural tendency of a pressurized garment to become a rigid, unbending balloon has been the central engineering conflict throughout the suit’s history. This report will trace the remarkable evolution of this human-shaped spacecraft, from its earliest origins as equipment for high-altitude aviators to the advanced systems being designed today for humanity’s return to the Moon and the eventual journey to Mars. It is a story of materials science, human physiology, and engineering ingenuity, a narrative that follows humanity’s own journey into the final frontier.

Part I: The Genesis of the Spacesuit

The story of the spacesuit doesn’t begin with rockets or dreams of other worlds. It begins in the sky, with the daredevil aviators and military pilots who first pushed their primitive aircraft to the edges of the atmosphere. Long before NASA existed, these pioneers encountered the life-threatening conditions of near-space and, out of necessity, invented the fundamental technologies that would one day allow humans to walk on the Moon.

The First Pressure Suits

The 1930s are often seen as a “Golden Age for aviation,” a time of record-setting flights and rapid technological advancement. As pilots flew higher, they discovered that simply breathing pure oxygen wasn’t enough. Above about 43,000 feet, the ambient air pressure is so low that the lungs cannot absorb enough oxygen to remain conscious, a condition known as “oxygen want”. The human body itself begins to suffer, with trapped gases expanding and body fluids threatening to boil. It became clear that to survive at these altitudes, a pilot needed to be encased in their own personal, pressurized atmosphere.

Early concepts drew inspiration from an existing technology designed to work under pressure: the diving suit. The core problem was similar – creating a fluid-tight seal against a pressure differential, whether it be water or air. In 1931, Soviet engineer Evgeniy Chertovsky created a full-pressure suit he called a “skafandr,” a term that in Russian means both “diving suit” and “spacesuit”. A few years later, in 1935, Spanish engineer Emilio Herrera designed a sophisticated “stratonautical space suit” for a planned high-altitude balloon flight, though it was never used for its intended purpose.

The first person to successfully fly in a practical pressure suit was the famed American aviator Wiley Post. In 1934, funded by Frank Phillips of the Phillips Petroleum Company, Post sought to fly in the stratosphere, where the thin air offered less resistance and promised higher speeds. Since his record-breaking Lockheed Vega aircraft, the Winnie Mae, had an unpressurized cabin, Post collaborated with Russell S. Colley of the B.F. Goodrich Company to create a suit that could keep him alive.

The final version of Post’s suit was a marvel of 1930s ingenuity. Its body consisted of three layers: a base of long underwear, an inner black rubber bladder to hold the air pressure, and an outer layer of rubberized parachute fabric to provide shape and restraint. The helmet was a metal creation resembling a large can, made of aluminum and plastic, with a window for visibility. Pigskin gloves and rubber boots completed the ensemble, which was supplied with liquid oxygen for breathing. In this suit, Post made a series of high-altitude flights, unofficially reaching heights near 50,000 feet. During these flights, he became the first person to consciously encounter and use the jet stream, at times achieving ground speeds over 340 miles per hour in a plane that could only fly at 179 mph on its own. Wiley Post’s flights were more than just aviation records; they were a proof of concept. They demonstrated that a human could be kept alive and functional inside a personal, pressurized bubble, laying the essential groundwork for all spacesuits to come.

Military Imperatives and Post-War Progress

While individual pioneers like Wiley Post pushed the boundaries of flight, the looming threat of World War II transformed pressure suit development from a niche pursuit into a military imperative. It was clear that aviation would play a dominant role in the coming conflict, and whichever side could solve the physiological problems of high-altitude flight would gain a decisive advantage.

During the late 1930s and early 1940s, the U.S. Army Air Force initiated the classified MX-117 project, contracting with B.F. Goodrich and Goodyear to produce full-pressure suits for the crews of high-flying bombers. These experimental suits, like the XH-5 model nicknamed the “Tomato Worm” for its ribbed, segmented appearance, were ambitious but ultimately unsuccessful. The core problem was mobility. When inflated, the suits became rigid and balloon-like, making it nearly impossible for a crew member to operate controls or move within the tight confines of an aircraft. The project was canceled in 1943, having failed to produce a practical design.

This failure highlighted a fundamental challenge in suit design and led to the development of a competing philosophy: the partial-pressure suit. Instead of enclosing the entire body in a loose, gas-filled bag, a partial-pressure suit uses a different principle. It is a skin-tight garment that applies direct mechanical pressure to the body to counteract the effects of low ambient pressure. The breakthrough came in 1945 from Dr. James Paget Henry at the University of Southern California. His S-1 suit used a system of air-filled bladders, similar to those in an anti-G suit, integrated into a tight-fitting garment. When the aircraft cabin depressurized, these bladders would inflate, squeezing the arms and legs to prevent the dangerous shift of body fluids. This mechanical counter-pressure, combined with a sealed helmet providing breathing oxygen, could keep a pilot alive during an emergency descent.

The David Clark Company refined this concept into the T-1 partial-pressure suit, which became the standard “get-me-down” emergency suit for the military and for the test pilots flying the early experimental X-Planes in the late 1940s and 1950s. These suits were not meant to be worn pressurized for long periods, but they offered a life-saving bridge back to the safety of thicker air.

This era also saw critical contributions from medical research. At the Mayo Clinic, a dedicated Aero-Medical Unit conducted secret research to solve the twin problems of “oxygen want” and the crushing “G” forces of high-speed aerial combat. Using human centrifuges and low-pressure chambers, they developed the G-suit, a full-body uniform with inflatable chambers that counteracted gravitational forces by directing blood flow back to the brain. They also invented advanced oxygen masks like the BLB Mask. These innovations were vital to the Allied war effort and directly informed the design of the life support systems that would become essential components of true spacesuits.

The early history of the pressure suit reveals that its development was not a simple, linear progression. It was a branching path, driven by two distinct and competing philosophies. The full-pressure approach, exemplified by Wiley Post’s suit and the military’s MX-117 project, aimed to create a stable, artificial atmosphere around the body. This offered comprehensive protection but at a great cost to mobility, as the suits became stiff and difficult to bend when inflated. The partial-pressure approach, pioneered with the S-1 and T-1 suits, prioritized mobility by applying a “mechanical squeeze” only where needed, but it was less comfortable and suitable only for short-term emergencies. This fundamental engineering trade-off between mobility and protection, between a gas-filled balloon and a mechanical corset, would define spacesuit design for decades to come. The solutions were not born from abstract dreams of space travel, but from the practical and urgent demands of commercial competition and military superiority.

Part II: The Dawn of the Space Age

With the launch of Sputnik in 1957 and the formal start of the Space Race, the pressure suit was abruptly thrust from the realm of high-altitude aviation into the new and far more demanding world of human spaceflight. The first generation of true spacesuits, developed for the pioneering Vostok, Voskhod, and Mercury programs, were not just pieces of safety equipment; they were national symbols. The divergent paths taken by the Soviet Union and the United States in their design revealed deeply different engineering philosophies, mission architectures, and approaches to risk in the quest to conquer the heavens.

The Soviet Pioneers: Vostok and Voskhod

The Soviet Union achieved the first great milestones of the human space age, and for each one, a new suit was developed by the NPP Zvezda enterprise, a manufacturer that began by making pressure suits for military pilots. These early suits were integral components of the mission, not just backups.

The SK-1: A Suit for the First Man in Space

The first spacesuit ever worn in space was the SK-1, an initialism for “Skafandr Kosmicheskiy #1,” or “diving suit for space #1”. It was developed specifically for one man and one mission: Yuri Gagarin and his historic flight aboard Vostok 1 on April 12, 1961.

The SK-1 was an Intra-Vehicular Activity (IVA) suit, meaning it was designed to be worn inside the spacecraft. Its primary purpose was to protect the cosmonaut during the dynamic phases of launch and reentry, and to provide life support in the event of an emergency cabin depressurization. Critically, its design was dictated by the unique landing profile of the Vostok spacecraft. Unlike American capsules, the Vostok was not designed for a soft landing with the cosmonaut inside. Instead, the mission plan called for the pilot to eject from the capsule at an altitude of about 8 kilometers (26,000 feet) and descend to the ground separately under his own parachute. The SK-1 was therefore not just a pressure suit; it was a personal survival system for a high-altitude bailout.

The suit’s appearance reflected this function. It featured a high-visibility, bright orange nylon oversuit to make the cosmonaut easy to spot after landing. The helmet was not detachable from the suit, forming a single integrated pressure vessel. An inflatable rubber collar was built into the neck ring, designed to act as a life preserver in the event of a water landing. The suit weighed approximately 20 kg (44 lbs) and maintained an internal pressure of about 4.0 psi. After Gagarin’s successful flight, the SK-series suits were used for all subsequent Vostok missions. A nearly identical version, the SK-2, was tailored for Valentina Tereshkova, the first woman in space.

The Berkut: A Suit for the First Spacewalk

Having conquered Earth orbit, the Soviets next set their sights on having a human leave the confines of a spacecraft. For the Voskhod 2 mission in March 1965, the SK-1 suit was modified to create the Berkut (“Golden Eagle”) suit, which would be worn by Alexei Leonov for the first Extra-Vehicular Activity (EVA) in history.

The Berkut was essentially an SK-1 with added layers for thermal insulation and, most importantly, a backpack life support system known as the KP-55. This backpack supplied Leonov with oxygen and vented away heat, moisture, and carbon dioxide, allowing him to survive untethered from the spacecraft’s internal environment.

The spacewalk was a moment of immense triumph for the Soviet program, but it very nearly ended in disaster. In the vacuum of space, the suit’s internal pressure caused it to inflate and become unexpectedly rigid, a phenomenon engineers call “ballooning”. While the risk was known, its severity was underestimated. Leonov’s hands slipped out of his gloves, and his feet came loose in his boots. He could not effectively control his movements. When it was time to return to the spacecraft, he discovered he was too stiff and bulky to fit back through the narrow, inflatable airlock. With his oxygen supply dwindling and his body temperature soaring, Leonov made a desperate and dangerous decision. Without informing mission control, he opened a valve on his suit and bled off precious air, reducing the internal pressure to a dangerously low level. This made the suit just flexible enough for him to squeeze headfirst into the airlock, exhausted and on the verge of heatstroke. Leonov’s harrowing experience was a stark and terrifying lesson: an IVA suit could not simply be adapted for EVA. The physics of a pressurized soft garment in a vacuum presented a significant challenge to mobility that would have to be solved before any meaningful work could be done in space.

America’s Response: Project Mercury

While the Soviets were designing bespoke suits for their specific mission profiles, NASA took a more pragmatic approach for Project Mercury, its first human spaceflight program. Rather than starting from scratch, the agency chose to adapt a proven piece of military hardware.

The Navy Mark IV: From Jet Pilot to Astronaut

After evaluating several options, including the suit used by X-15 rocket plane pilots, NASA selected the U.S. Navy’s Mark IV high-altitude pressure suit in 1959. Developed by the B.F. Goodrich Company, the Mark IV was designed by Russell Colley, the same engineer who had created Wiley Post’s pioneering suit two decades earlier. It was chosen because it was lighter and less bulky than its competitors and could be easily modified for the new role of a “space suit”.

The modifications for Project Mercury were significant. The suit’s original dark gray or green nylon outer shell was replaced with a layer of heat-reflective, aluminized nylon fabric to help with thermal control in the intense sunlight of orbit. The breathing system was converted from a simple “open loop” to a “closed loop” system. Oxygen was piped into the suit, circulated around the astronaut’s body for cooling, and then exited through the helmet, a more efficient design. Each suit was custom-fitted to one of the seven Mercury astronauts and weighed about 10 kg (22 lbs).

The Mercury suit’s function was fundamentally different from its Soviet counterpart. It was a pure backup system, a “get-me-down” garment that was worn unpressurized. It was only intended to inflate and save the astronaut’s life in the event of an unexpected and catastrophic loss of cabin pressure – an emergency that, fortunately, never occurred during any of the Mercury flights.

The designs of these first-generation spacesuits reveal the deeply different engineering philosophies that characterized the early Space Race. The Soviet SK-1 was an active and essential component of the Vostok mission architecture. The mission could not succeed without it, as the cosmonaut’s survival depended on the suit’s performance during the planned high-altitude ejection. This shows a Soviet approach that designed for a complex, multi-stage landing procedure where the suit played a critical role. In contrast, the American Mercury suit was a passive, redundant safety device. The mission plan relied entirely on the integrity of the spacecraft capsule for a safe landing; the suit was a layer of insurance against an unplanned failure. This reflects an American approach that prioritized the robustness of the primary vehicle, treating the suit as a secondary system. Both were valid paths to putting a human in orbit, but they demonstrated contrasting views on risk, redundancy, and the role of the human within the larger machine.

Part III: The Giant Leap

The years between 1965 and 1969 saw a period of incredibly rapid and revolutionary advancement in spacesuit technology. The lessons learned from the first tentative steps into orbit were applied to solve the immense challenges of long-duration flight, complex spacewalks, and ultimately, exploring the surface of another world. This era, defined by the Gemini and Apollo programs, transformed the spacesuit from a simple pressure garment into a true, autonomous spacecraft, culminating in the iconic A7L suit that allowed humanity to take its first steps on the Moon.

Gearing Up for EVA: The Gemini Suit

Project Gemini served as the important bridge between the single-astronaut flights of Mercury and the ambitious lunar missions of Apollo. Its primary purpose was to develop and master the technologies and skills necessary for a trip to the Moon, with a particular focus on rendezvous, docking, and, most importantly, Extra-Vehicular Activity. Alexei Leonov’s near-fatal spacewalk had made it painfully clear that a new kind of suit was needed – one that was not just a survival garment, but a functional tool for working in a vacuum.

The G3C and G4C: A New Generation

The David Clark Company, which had manufactured the partial-pressure suits for the X-Plane program, was tasked with developing the suits for Gemini. The resulting designs were a significant leap forward from the modified Mercury suit. The first flight version, the G3C worn on the Gemini 3 mission, introduced a key innovation to combat the “ballooning” effect: a link-net restraint layer. This was a mesh net woven from strong Dacron and Teflon cords that was worn over the inner, rubberized nylon pressure bladder. Because the net was slightly smaller than the bladder, it physically restrained the suit when pressurized, preventing it from expanding into a rigid, immobile balloon. This net acted as a structural shell, much like a tire contains the pressure of an inner tube, making the entire suit more flexible and controllable.

The G4C suit was the definitive EVA version, worn by Ed White during America’s first spacewalk on Gemini 4 and on most subsequent Gemini missions. It built upon the G3C’s foundation with critical additions for surviving the harsh environment outside the spacecraft. For thermal protection against the extreme temperature swings between direct sunlight (121 °C / 250 °F) and shadow (-157 °C / -250 °F), the G4C incorporated additional layers of super-insulating, aluminized Mylar. The outer layer was made of white Nomex, a heat- and flame-resistant fabric.

The suit continued to evolve based on mission experience. During Eugene Cernan’s grueling Gemini 9A spacewalk, he was slated to test the Air Force’s experimental Astronaut Maneuvering Unit (AMU), a jetpack-like device. To protect his legs from the AMU’s hot thruster exhaust, his G4C suit was reinforced with an outer layer of Chromel-R, a woven fabric of stainless steel fibers. Despite these improvements, Cernan’s spacewalk demonstrated that there were still major challenges to overcome. He became so overheated and exhausted from fighting the suit’s resistance that his helmet visor completely fogged over, blinding him. The experience proved that even with better mobility, managing an astronaut’s body heat was a fundamental problem that air cooling alone could not solve.

Life support for the Gemini suits also represented a new approach. Primary oxygen and power were supplied from the spacecraft through an umbilical cord. For spacewalks, astronauts relied on chest-mounted life support units. Ed White on Gemini 4 used a simple Ventilation Control Module (VCM) to manage oxygen flow. Later missions used the more advanced Extravehicular Life Support System (ELSS), a larger chest pack that could provide up to 30 minutes of emergency backup life support if the umbilical connection was severed.

The Apollo A7L: A Spacesuit for the Moon

The Apollo program demanded a spacesuit unlike any that had come before. It had to be more than just a garment for surviving in zero gravity; it had to be a complete, self-contained personal spacecraft that could protect an astronaut on the rugged, hostile surface of another world for up to eight hours. The resulting A7L suit remains one of the most complex and iconic pieces of engineering in human history.

Designing a Lunar Spacecraft

The development of the Apollo suit brought together a unique and, at the time, unconventional partnership. The contract was awarded to a team that included Hamilton Standard, an established aerospace contractor responsible for the life support systems, and International Latex Corporation (ILC), a division of the Playtex company, best known for making women’s bras and girdles. ILC’s decades of experience in creating form-fitting, flexible, and durable garments from rubber and fabric gave them an unexpected edge. Their expertise in industrial sewing and molding rubber proved to be precisely what was needed to build the suit’s complex, flexible pressure garment, allowing them to beat proposals from more traditional military contractors.

The suit was a bespoke creation. Each one was meticulously hand-stitched and custom-tailored for its specific astronaut, a process that required 64 different body measurements and multiple fittings to ensure a perfect fit. The development was iterative, but a tragic event forced a critical redesign. After the deadly Apollo 1 fire in 1967, in which the crew perished in a pure-oxygen, high-pressure cabin environment, the suit was upgraded with fire-resistant materials. This new, safer version was designated the A7L.

The Layers of Protection: A Detailed Breakdown

The A7L was a masterpiece of materials science, a soft suit composed of numerous layers, each with a specific and vital function. An astronaut dressing for a moonwalk would don these layers in sequence, building their personal spacecraft around them.

The Liquid Cooling and Ventilation Garment (LCVG): The first layer to go on was perhaps the most revolutionary innovation of the entire suit. The overheating and exhaustion that plagued Gemini spacewalkers had to be solved for Apollo. The solution was the LCVG, a one-piece undergarment made of nylon-spandex mesh that fit snugly against the body. Woven into this mesh was a network of over 90 meters (300 feet) of fine PVC tubing. During a spacewalk, chilled water was constantly pumped through these tubes, circulating across the astronaut’s body to directly absorb and carry away the immense amount of heat generated by strenuous work. This system was far more effective than the gas cooling used in Gemini and was the key enabling technology that made long, productive moonwalks physically possible. Without it, astronauts would have been limited to brief, exhausting excursions.

The Pressure Garment Assembly (PGA): This was the heart of the suit, the part that held in the life-sustaining atmosphere. It consisted of an inner comfort layer of lightweight, fire-resistant Nomex, a neoprene-coated nylon pressure bladder that was the airtight gas-retention layer, and a robust outer nylon restraint layer to prevent the bladder from ballooning. To provide mobility, the suit featured convoluted, bellows-like joints made of molded rubber at the shoulders, elbows, wrists, hips, ankles, and knees. These joints were designed to bend and flex while maintaining a relatively constant internal volume, reducing the effort needed to fight against the suit’s pressure.

The Integrated Thermal Micrometeoroid Garment (ITMG): Worn over the PGA, the ITMG was the suit’s white outer shield, its armor against the harshness of the lunar environment. This removable over-garment was a complex laminate of at least 13 distinct layers. From the inside out, it began with a layer of rubber-coated nylon for micrometeoroid protection. This was followed by five layers of super-insulating, aluminized Mylar film, each separated by a spacer layer of non-woven Dacron to create a vacuum gap, functioning like a high-tech thermos. Next came two layers of aluminized Kapton film laminated to Beta marquisette for extreme heat protection. The outermost layer was made of Beta cloth, a specially developed, woven fiberglass fabric coated with Teflon to make it both fireproof and resistant to abrasion. For extra durability against the sharp, abrasive lunar dust, patches of woven stainless-steel Chromel-R fabric were added to the knees, shoulders, and the uppers of the lunar boots.

The Portable Life Support System (PLSS)

The iconic “backpack” worn by the Apollo astronauts was the Portable Life Support System, or PLSS. Manufactured by Hamilton Standard, this unit was what transformed the A7L suit into a truly autonomous spacecraft, allowing astronauts to explore the lunar surface for hours, completely untethered from their lander.

The PLSS was a marvel of miniaturization, containing all the systems needed for survival. It housed a tank of high-pressure oxygen for breathing and for maintaining the suit’s 3.7 psi internal pressure. As the astronaut breathed, a fan circulated the oxygen through the suit. The exhaled air returned to the backpack, where it passed through a replaceable canister containing lithium hydroxide (LiOH), a chemical that scrubbed the toxic carbon dioxide from the air. The backpack’s battery-powered pump circulated the water through the LCVG to cool the astronaut. This heated water then flowed to a device called a sublimator. Here, the water was exposed to the vacuum of space through a porous plate. This caused the water to instantly freeze and then sublimate – turn directly from a solid (ice) to a gas (water vapor). This phase change wicked an enormous amount of heat away from the cooling loop, efficiently rejecting it into space. The PLSS also contained the radio for communications with the lander and Mission Control, and a battery to power the entire system. Mounted on top of the PLSS was the Oxygen Purge System (OPS), a separate, emergency oxygen supply that could provide about 30 minutes of breathable air in a high-flow purge in case the main backpack failed.

Part IV: Living and Working in Orbit

Following the triumph of the Apollo program, the focus of human spaceflight shifted from the sprint to the Moon to the marathon of long-term habitation in low Earth orbit. This new era, defined by the Space Shuttle and the construction of space stations like Mir and the International Space Station (ISS), demanded a new philosophy in spacesuit design. The bespoke, single-mission suits of Apollo gave way to reusable, modular workhorses – durable, serviceable systems designed to support hundreds of spacewalks over many years. This period saw the rise of two dominant designs: NASA’s Extravehicular Mobility Unit (EMU) and the Russian Orlan suit, each a reflection of its agency’s approach to living and working in space.

The Workhorse: NASA’s Extravehicular Mobility Unit (EMU)

The Extravehicular Mobility Unit, or EMU, became the backbone of American spacewalking for more than three decades. Developed in the 1970s and first used during the Space Shuttle program in 1982, the EMU was designed for the routine work of satellite repair, spacecraft maintenance, and the complex assembly of the International Space Station. It has been used for over 200 successful spacewalks, a testament to its robust and adaptable design.

The EMU’s defining characteristic is its modularity. Unlike the Apollo A7L, which was custom-fitted for a single astronaut, the EMU is a two-piece, semi-rigid suit with interchangeable components. This was a critical design choice driven by the logistics of the Shuttle and ISS programs. Instead of flying a new set of custom suits for every mission, NASA could stock a collection of standard-sized parts on orbit and assemble them as needed. This modularity allows the EMU to be reconfigured to fit a wide range of astronaut body types, from a 5th percentile female to a 95th percentile male, making it a far more cost-effective and versatile system for long-term use.

The suit consists of two main sections. The Hard Upper Torso (HUT) is a rigid, one-size-fits-all vest made of fiberglass that serves as the structural core of the entire assembly. The life support backpack, arms, and helmet all attach to the HUT. The Lower Torso Assembly (LTA) is a soft component that includes the waist, legs, and boots, and comes in various sizes. To don the suit, an astronaut first puts on the LTA trousers, then slides up into the HUT, connecting the two halves with a secure, rotating Body Seal Closure at the waist. The arms and gloves are also modular and are attached with locking rings.

The materials of the EMU represent an evolution of the technologies perfected during Apollo. The outer layer is made of a different material called Ortho-Fabric. This is an extremely tough, white, woven material that blends three different fibers: Gore-Tex for waterproofing, Kevlar for tear and puncture resistance (the same material used in bullet-proof vests), and Nomex for fire resistance. This durable outer shell protects the inner insulation and pressure layers from the rigors of orbital construction work. When fully assembled with its life support backpack and SAFER rescue jetpack, the ISS version of the EMU weighs approximately 145 kg (319 lbs) on Earth. Its operational history is extensive, from its first EVA on the STS-6 mission in 1983 to its indispensable role in building and maintaining the ISS today.

The Russian Counterpart: The Orlan Suit

The Soviet, and later Russian, equivalent to the EMU is the Orlan (“Sea Eagle”) series of spacesuits. A veteran of the Salyut, Mir, and ISS programs, the Orlan has a long and successful history of its own, with its design roots tracing back to the Kretchet suit, which was originally intended for the canceled Soviet crewed lunar program.

The Orlan’s most distinctive feature, and the one that sets it apart from American designs, is its rear-entry system. The suit is a semi-rigid, one-piece garment where the life support backpack is integrated directly into the suit and hinges open like a door. A cosmonaut dons the suit not by assembling pieces, but by opening the rear hatch, “backing in” to the suit, and closing the hatch behind them. This elegant design allows a single crew member to get into the suit and seal it without assistance in about five minutes – a significant operational advantage for routine tasks compared to the more complex, multi-part EMU, which requires help from another crew member and more time to assemble.

Like the EMU, the Orlan is designed to be stored aboard the space station and serviced in orbit. It has evolved through a series of models – from the Orlan-D first used on Salyut 6 in 1977, to the DM, DMA, M, MK, and the current MKS model used on the ISS. With each iteration, its capabilities have improved, with life support duration increasing from an initial 3 hours to over 7 hours today. The suit’s semi-rigid construction features a hard aluminum alloy torso with flexible arms and legs. Another key difference is its operating pressure. The Orlan operates at a higher pressure of approximately 5.8 psi, compared to the EMU’s 4.3 psi. This higher pressure reduces the amount of time a cosmonaut must “pre-breathe” pure oxygen to purge nitrogen from their bloodstream before a spacewalk, another factor that streamlines EVA preparations.

The design differences between the EMU and the Orlan reflect a fundamental divergence in human factors philosophy. The American EMU is a component-based, modular system that prioritizes a highly customized fit for a diverse astronaut corps, even at the cost of a more complex and time-consuming suiting-up process. The Russian Orlan is an integrated, “walk-in” system that prioritizes speed, autonomy, and simplicity of operation. Neither approach is inherently superior; they are simply different solutions to the same problem, each optimized for slightly different operational priorities in the context of long-term life in orbit.

China’s Entry: The Feitian Suit

In 2008, China became only the third nation in the world to independently conduct a spacewalk, using its indigenously developed Feitian (“Flying to the Heavens”) spacesuit. The development of this suit is a classic example of strategic technology acquisition followed by domestic iteration.

In the early 2000s, as part of its ambitious human spaceflight program, China signed an agreement with Russia to purchase a number of Orlan-M spacesuits. These suits were used for training, study, and to jump-start China’s own EVA suit development program. The first-generation Feitian suit, worn by taikonaut Zhai Zhigang during his historic first spacewalk on the Shenzhou 7 mission, was heavily based on the Orlan design. It shares the same semi-rigid, rear-entry architecture and is visually very similar.

While retaining the robust and well-understood mechanical design of the Orlan, Chinese engineers focused on upgrading the suit’s internal systems. They claim the Feitian incorporates more modern digital electronics, data processing, and communication systems compared to the older, analog-based technology of the Orlan-M model it was based on. This approach – learning from a proven system, copying its fundamental architecture, and then innovating on specific subsystems – allowed China to bypass decades of difficult initial research and development and rapidly achieve its own independent EVA capability. Today, a second-generation Feitian suit is in use on the Tiangong space station. It has an increased EVA duration of up to 8 hours and is designed to be used up to 15 times, cementing China’s status as a major space-faring power.

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Part V: The New Space Age: Commercial and Exploration Suits

The current era of space exploration is defined by two powerful, parallel forces: a renewed governmental focus on returning humans to the Moon, and the disruptive rise of commercial spaceflight companies. This has ignited a new wave of spacesuit development, with NASA partnering with private industry to create the suits for its Artemis program, and companies like SpaceX developing their own systems from the ground up. The result is a dynamic landscape of innovation, where lessons from the past are being combined with 21st-century technology and novel business models.

Returning to the Moon: The Artemis Program

NASA’s Artemis program aims to land the first woman and the next man on the Moon, establishing a long-term human presence there as a stepping stone to Mars. This requires a new generation of lunar spacesuits, capable of meeting the challenges of surface exploration in the rugged and treacherous terrain of the lunar south pole.

The AxEMU: A Commercial Approach

For decades, NASA developed its own spacesuits in-house or through traditional contracting methods. The agency spent over 14 years and more than $420 million developing a new prototype called the Exploration Extravehicular Mobility Unit (xEMU). However, facing significant schedule delays, NASA pivoted to a new and fundamentally different procurement strategy. Instead of building the suits itself, the agency is now contracting for “moonwalking services” from commercial partners under a program called Exploration Extravehicular Activity Services (xEVAS).

Under this new model, NASA has awarded a task order to a Houston-based company, Axiom Space, to develop, own, and operate the suits that will be worn by the Artemis III astronauts. The resulting suit is called the Axiom Extravehicular Mobility Unit (AxEMU). Axiom Space is building upon NASA’s foundational research from the xEMU project but is responsible for the final design, manufacturing, testing, and certification. This approach marks a major shift in the relationship between NASA and private industry, turning the agency from a developer into a customer. The goal is to foster a competitive commercial market for space services, reduce long-term costs for the taxpayer, and leverage private sector agility to accelerate development.

The design of the AxEMU is a direct response to the hard-won lessons of the Apollo program. Its key goals are to solve the specific problems that limited the first moonwalkers:

• Enhanced Mobility: The single greatest limitation of the Apollo A7L suit was its stiffness, particularly in the lower body, which led to the characteristic “bunny hop” gait. The AxEMU features a completely redesigned lower torso with advanced, constant-volume joints and bearings at the hips, knees, and ankles. This will allow astronauts to walk naturally, bend, kneel down to inspect rocks, and even squat, providing a range of motion far superior to what was possible in the 1960s.
• Dust Mitigation: The Apollo missions revealed that lunar dust is a major hazard. It is fine, sharp like tiny shards of glass, and electrostatically charged, causing it to cling to everything. It abraded suit fabrics, clogged mechanisms, and was a respiratory concern when tracked back into the lunar module. The AxEMU is being designed with a suite of dust-tolerant features, including advanced seals and materials, to prevent inhalation and protect the suit’s critical systems.
• Wider Fit Range: The AxEMU is a modular suit designed to accommodate at least 90% of the American male and female population. This inclusive sizing is a core requirement, ensuring that a broad range of astronauts can participate in lunar surface missions and enabling the first woman to walk on the Moon.
• Advanced Technology: The suit incorporates modern features, including a rear-entry hatch for easier donning (similar to the Russian Orlan), a highly redundant Portable Life Support System (PLSS) for increased safety, and an advanced helmet and visor system.

Reflecting its commercial nature, Axiom Space has formed unique partnerships with companies outside the traditional aerospace sector. It is collaborating with the Italian luxury fashion house Prada to leverage their expertise in composite materials and innovative sewing methods for the suit’s white outer thermal garment. It has also partnered with the high-performance optics company Oakley to design and build the advanced visor system, which must provide clarity and protection from the harsh glare and deep shadows of the lunar south pole.

The Rise of Commercial Spaceflight

While Axiom develops suits for NASA’s government-led missions, other companies are creating their own systems for a purely commercial market.

SpaceX’s Vision

SpaceX has taken a distinct, vertically-integrated approach to spacesuit design, treating it as another component of its overall transportation system. The sleek, minimalist white-and-black IVA suit worn by astronauts on the Crew Dragon spacecraft broke with traditional aesthetics. It was famously designed with input from Hollywood costume designer Jose Fernandez, known for his work on superhero films, reflecting founder Elon Musk’s desire for an inspirational and futuristic look.

More significantly, SpaceX has evolved this IVA suit into a new EVA suit, designed to support the first-ever commercial spacewalk on the upcoming Polaris Dawn mission. This suit represents a significant upgrade, incorporating new thermal management textiles and materials borrowed from the Falcon rocket’s interstage and Dragon’s trunk for durability. It features enhanced mobility joints to allow for movement in a vacuum and, most notably, a 3D-printed helmet with an integrated Heads-Up Display (HUD) and camera. This HUD provides the spacewalking astronaut with real-time data on suit pressure, temperature, and humidity directly in their field of view, a feature not present in current NASA or Russian suits.

SpaceX’s stated long-term goal is to create a scalable design that can be mass-produced, looking ahead to a future where millions of spacesuits might be needed for building a base on the Moon and a city on Mars. This ambition frames their current development not just as a one-off project, but as an early step toward equipping a multi-planetary humanity.

Part VI: The Anatomy of a Spacesuit: A Technological Deep Dive

While spacesuits have evolved dramatically over the decades, the fundamental challenges of keeping a human alive in a vacuum remain the same. All modern EVA suits, whether American, Russian, or Chinese, are built around a core set of sophisticated technologies designed to provide life support, mobility, and protection. Understanding these key subsystems reveals the incredible complexity hidden beneath the suit’s white outer layer.

Core Systems and Technologies

A modern spacesuit is a system of interconnected systems, where every component choice has a ripple effect on the entire design. A decision made to enhance protection can impact mobility, which in turn affects cooling requirements, which adds weight and complexity to the life support system. The final product is always a carefully optimized balance of these competing demands.

Life Support in a Backpack

The heart of any autonomous spacesuit is its life support backpack, known in NASA terminology as the Portable Life Support System (PLSS). This unit contains all the equipment necessary to create a habitable environment inside the suit for up to eight hours.

• Oxygen Supply and Pressurization: The PLSS contains tanks of high-pressure gaseous oxygen. This oxygen serves two purposes. First, it provides the breathable atmosphere for the astronaut. Second, a series of regulators releases the gas into the suit to maintain a constant, stable internal pressure – typically between 4.3 psi for the American EMU and 5.8 psi for the Russian Orlan. This pressure is lower than sea-level pressure on Earth (14.7 psi), which helps make the suit more flexible, but it requires astronauts to pre-breathe pure oxygen for a period before a spacewalk to purge nitrogen from their bodies and prevent decompression sickness.
• Carbon Dioxide Removal: A human’s exhaled breath contains toxic carbon dioxide, which must be continuously removed from the suit’s atmosphere. A fan inside the PLSS circulates the air from the suit through a scrubbing system. In the Apollo and Shuttle/ISS EMU suits, this is accomplished using canisters filled with lithium hydroxide (LiOH). The LiOH chemically reacts with the CO2, trapping it in the form of solid lithium carbonate. These canisters are non-regenerable and must be replaced after each use. Future systems are exploring technologies like pressure swing adsorption (PSA), which could separate the CO2 and vent it into space, allowing the system to be “recharged” and reused multiple times.
• Thermal Control: Managing an astronaut’s body heat during a strenuous spacewalk is one of the most critical functions of the PLSS. The primary tool for this is the Liquid Cooling and Ventilation Garment (LCVG), the spandex-and-nylon undergarment with a network of water-carrying tubes. A pump in the PLSS circulates chilled water through these tubes, where it absorbs the astronaut’s body heat. This warmed water then returns to the PLSS and flows through a device called a sublimator. The sublimator is a heat exchanger with a porous metal plate exposed to the vacuum of space. As the warm water flows through it, a small amount of separate feedwater seeps through the pores and is exposed to the vacuum. This water instantly freezes and then sublimates (turns from solid ice directly to water vapor), a process that consumes a large amount of thermal energy. This energy is pulled from the main cooling loop, thus chilling the water before it is sent back to the LCVG to cool the astronaut again. This clever system allows the suit to dump massive amounts of waste heat into space without any complex refrigeration machinery.

The Battle for Mobility: Joints and Bearings

The greatest obstacle to a functional spacesuit is the physics of a pressurized garment. A simple, sealed fabric tube, when filled with air, becomes incredibly stiff and resists bending. This is the “ballooning” effect that nearly killed Alexei Leonov. Overcoming this requires sophisticated joint designs.

Early suits like the Mercury Mark IV used simple fabric break lines sewn into the elbows and knees, which offered very limited mobility. The true breakthrough came with the development of constant-volume joints. These are complex, bellows-like structures, typically made of molded rubber, that are designed to fold and bend without significantly changing the total internal volume of the joint. Because the volume doesn’t change, the astronaut doesn’t have to do extra work to compress the air inside every time they bend a limb. This drastically reduces fatigue and makes movement easier. These types of joints are used in the shoulders, elbows, hips, and knees of modern suits like the EMU and the upcoming AxEMU.

While bellows joints allow for bending, they do not allow for rotation. To permit an astronaut to twist their wrist or turn at the waist, suits incorporate mechanical bearings. These are circular assemblies, often containing hundreds of tiny ball bearings, that allow one part of the suit to rotate smoothly relative to another. They are typically found at the shoulders, upper arms, wrists, and waist. Early bearings were made of heavy stainless steel, but to save precious weight, modern designs have shifted to lighter materials like titanium and advanced composites. The combination of constant-volume bending joints and rotating bearings is what gives a modern spacesuit its range of motion.

The Helmet and Visor Assembly

An astronaut’s helmet is far more than a simple window; it is a complex subsystem responsible for vision, communications, and maintaining the pressure bubble around the head.

The foundation of the helmet is the pressure bubble itself, a transparent dome typically molded from high-strength polycarbonate plastic. This bubble locks onto the suit’s neck ring to form an airtight seal. Over this bubble fits the Extravehicular Visor Assembly (EVVA). This is a protective shell that contains multiple, movable visors. It typically includes a clear protective visor to shield the main bubble from scratches and impacts, an inner sun shade, and the main sun visor. This main visor is coated with a microscopically thin layer of gold, which is highly effective at reflecting the sun’s intense heat and harmful radiation while still allowing the astronaut to see through it.

Communications are also integrated into the helmet assembly. For decades, this took the form of the iconic fabric “Snoopy cap,” a close-fitting cap worn under the helmet that had built-in earphones and microphones. Newer suits, like the xEMU and AxEMU, are moving toward systems with multiple voice-activated microphones embedded directly into the helmet’s interior, eliminating the need for the separate cap and improving audio clarity. Some helmets also include a small foam block positioned so an astronaut can move their head to scratch an itchy nose – a small but important human comfort in a highly restrictive environment.

The Challenge of Gloves

Across decades of spacewalking experience, astronauts consistently identify one part of the suit as the most difficult and fatiguing to work with: the gloves. The hands are an astronaut’s primary tool for interacting with the world, and the gloves must somehow provide protection from a complete vacuum, extreme temperatures, and sharp objects, while simultaneously allowing for the dexterity and tactile feedback needed to operate tools, flip switches, and grip handrails.

This set of conflicting requirements makes glove design arguably the most challenging aspect of engineering a spacesuit. Like the suit itself, gloves are made of multiple layers. They start with an inner pressure bladder, custom-molded from a 3D scan or plaster cast of the astronaut’s hand to ensure a snug fit. This is covered by a restraint layer to control its shape, and an outer Thermal Micrometeoroid Garment (TMG) for protection. The materials are highly specialized: fingertips are often made of blue silicone rubber to provide some measure of tactility, while the palms and other high-wear areas are reinforced with super-strong fabrics like Chromel-R or Vectran to resist abrasion. To combat the intense cold of space, many modern gloves have integrated electrical heaters in the fingertips.

Despite these advances, the simple act of closing one’s hand inside a pressurized glove requires fighting against the pressure of the entire suit, leading to severe hand fatigue and, in many cases, painful injuries like abrasions and fingernail delamination (onycholysis). Improving glove performance remains one of the highest priorities for the designers of the next generation of spacesuits.

Summary

The spacesuit has undergone a remarkable journey of evolution, from the crude, modified diving suits and high-altitude gear of the 1930s to the sophisticated, multi-layered personal spacecraft of today. This progression was not driven by a single vision but by the changing demands of exploration. Each new era of human spaceflight presented a new set of challenges, forcing engineers to develop new materials, new technologies, and new design philosophies.

Throughout this history, a central engineering conflict has persisted: the constant battle between providing robust protection and enabling human mobility. The suit must be a fortress, shielding its occupant from the lethal vacuum, extreme temperatures, and radiation of space. Yet it must also be a tool, flexible enough to allow an astronaut to walk, work, and conduct delicate scientific tasks. The story of the spacesuit is the story of this trade-off.

The early days of the Space Race produced bespoke, mission-specific suits like the Soviet SK-1, an integral part of the Vostok landing system, and the American Mercury suit, a passive backup garment. The Apollo program culminated in the legendary A7L, a custom-fitted lunar spacecraft that introduced revolutionary technologies like the liquid cooling garment, making long, strenuous moonwalks possible. The Space Station era ushered in a new philosophy of reusability and serviceability, giving rise to the modular American EMU and the rapid-donning Russian Orlan, durable workhorses designed for hundreds of routine spacewalks in Earth orbit.

Today, we are in a new, dynamic era. A renewed push to explore the Moon under the Artemis program and the rise of a vibrant commercial space industry are once again reshaping spacesuit design. NASA is partnering with companies like Axiom Space to develop the next generation of lunar suits as a commercial service, while innovators like SpaceX are creating their own systems with an eye toward a multi-planetary future. As humanity sets its sights on new and more challenging destinations like Mars, the spacesuit will continue to evolve. It will demand new materials that are more resistant to abrasive dust, new life support systems that are more efficient and regenerable, and new designs that provide even greater mobility and autonomy. The human-shaped spacecraft, the ultimate expression of our drive to explore, is still being perfected.