The Orlan-MKS EVA Suit

A Marvel of Engineering

The Orlan-MKS spacesuit is a marvel of engineering, serving as the primary extravehicular activity (EVA) suit for Roscosmos cosmonauts. It is not merely a piece of clothing but a self-contained, human-shaped spacecraft. It provides life support, protection, and mobility for crew members working in the lethal vacuum of space outside the International Space Station. Developed and manufactured by NPP Zvezda, the Orlan-MKS is the latest iteration in a long and proven line of spacesuits that date back to the Soviet space program.

This article explores the design, history, components, and operational use of the Orlan-MKS, a suit defined by its unique rear-entry system and its robust, on-orbit serviceability. Its design philosophy differs significantly from its American counterparts and represents a lineage of incremental, practical refinement over nearly five decades.

A Legacy of Spacewalks

The Orlan suit family was born from the needs of the Soviet Union’s Salyut orbital space station program. The very first spacewalk, conducted by Alexei Leonov in 1965, used a different, single-use “soft” suit called the Berkut. That experience, which nearly ended in tragedy when the suit balloonized, highlighted the need for a more durable and reliable suit for regular, sustained work outside a space station.

The first Orlan model, the Orlan-D, was introduced in 1977 for use on the Salyut 6 station. From its inception, the Orlan featured its most defining characteristic: a semi-rigid design with a rear-entry hatch. This innovative approach allowed a cosmonaut to don the suit quickly and without assistance, a major advantage inside the cramped quarters of a small space station.

Through the 1980s, the suit was upgraded for the Mir space station. The Orlan-DM, Orlan-DMA, and Orlan-M models each brought improvements. They increased the duration of spacewalks (EVAs), enhanced joint mobility, and incorporated better avionics. The Orlan-M, introduced in 1997, became the workhorse for the final years of Mir and the initial construction of the International Space Station. These suits were designed from the start not as disposable items, but as permanent, serviceable assets of the space station itself.

The Orlan-MK, introduced in 2009, was a significant modernization that incorporated a mini-computer to process telemetry and system data. This “computerized” model set the stage for the next great leap.

The Orlan-MKS (“Modernized, Computerized, Synthetic”) is the current-generation suit, first flown in 2017. It represents a deep upgrade to the proven Orlan-MK. The “MKS” designation highlights its key features: it is modernized with a fully automatic thermal control system, it retains the advanced computerized diagnostics of its predecessor, and it incorporates new synthetic materials to replace older, rubber-based components. This latest model is lighter, more durable, and significantly easier for the cosmonaut to operate, freeing them to focus on the complex tasks of station maintenance.

Design Philosophy of the Orlan

The Orlan-MKS is best understood by its two core design principles: its semi-rigid structure and its rear-entry hatch. This combination makes it fundamentally different from the NASA Extravehicular Mobility Unit (EMU), which is a modular suit assembled from separate upper and lower torso pieces.

The Semi-Rigid Shell

The suit is “semi-rigid” because it combines a solid metal torso with flexible, multi-layered fabric limbs. The core of the suit is the hard upper torso, or “cuirass.” This component is a single, lightweight, and extremely strong shell made of an aluminum alloy. It acts as the suit’s chassis, protecting the cosmonaut’s upper body from impacts and providing a rigid, stable platform.

This hard torso is the structural anchor for all the suit’s most important components. The flexible arms, the helmet, the electrical and fluid umbilicals, and the main life support backpack are all mounted directly to this central shell. This design contrasts with a “soft suit” (like the Apollo-era suits), which is made entirely of fabric and relies on internal pressure to become rigid. The Orlan’s hard torso provides consistent shape and protection, regardless of internal pressure.

The arms and legs are soft, flexible components. They are attached to the hard torso via high-mobility joints, allowing the cosmonaut to move and bend against the suit’s internal pressure. While the hard torso is one-size-fits-all, the soft limbs can be adjusted on the ground before flight to accommodate cosmonauts of different heights and reaches, typically from 165 to 190 centimeters (about 5’5″ to 6’3″).

The Rear-Entry Hatch

The most iconic feature of the Orlan is its entry system. The entire backpack, which contains the complete Portable Life Support System (PLSS), is a single, massive hatch. This hatch is hinged at the side and swings open like a refrigerator door, revealing a large opening in the back of the hard torso.

To don the suit, a cosmonaut simply opens the hatch, floats over to the suit, and “walks” into it backward, feet-first. They slide their legs into the boots, push their arms into the sleeves, and then pull their head and shoulders up into the torso and helmet cavity. Once inside, they grab an internal lanyard or handle and pull the backpack hatch closed, sealing it with a simple but robust latching mechanism.

The entire process is remarkably fast and efficient, capable of being completed by a single person in about five to ten minutes. This self-donning capability is a powerful logistical advantage. It eliminates the need for a second crew member to assist, a process that can be time-consuming and complex with modular suits like the American EMU, which must be assembled around the astronaut. The Orlan’s “climb in and close the door” design is a testament to its focus on operational simplicity and crew autonomy.

Anatomy of the Orlan-MKS

Each Orlan-MKS suit is a complex, multi-layered system designed to protect its occupant from the most hostile environment known. It provides a pressurized, oxygen-rich atmosphere, manages temperature extremes, scrubs carbon dioxide, and shields against radiation and micrometeoroids.

The Multi-Layered Structure

Like all modern spacesuits, the Orlan-MKS is not a single garment but a composite of many layers, each with a specific function. Working from the inside out, these layers perform distinct roles.

Closest to the cosmonaut’s skin is the Liquid Cooling and Ventilation Garment (LCVG). This is not technically part of the suit itself but is an essential undergarment. It looks like a set of long johns and is threaded with a vast network of thin, flexible plastic tubes. Chilled water, supplied by the backpack, is continuously pumped through these tubes to draw excess body heat directly from the cosmonaut’s skin. Without this, the cosmonaut would quickly overheat from their own metabolic energy, as the suit is a perfect insulator. The garment also includes ventilation ducts that pull moist air away from the body to keep the wearer dry.

Next is the pressure bladder. This is the layer that actually holds the air in. In the Orlan-MKS, this is a key upgrade. Older Orlan suits used bladders made of rubber, which degrades over time. The “S” in MKS stands for “Synthetic,” referring to the new polyurethane bladder. This material is far more durable, less prone to cracking or leaking, and lighter than rubber. This single change is a primary reason for the MKS’s extended service life.

Over the pressure bladder is a restraint layer. This is a strong, woven fabric layer that is precisely tailored to the shape of the bladder. Its job is to prevent the bladder from ballooning outward under pressure. This layer is what gives the suit its human shape and provides the resistance the cosmonaut feels when they try to bend a joint.

Finally, the Thermal Micrometeoroid Garment (TMG) forms the suit’s outer skin. This is the familiar white, bulky exterior. It is itself a composite of multiple layers, including aluminized Mylar (for reflecting solar radiation) and durable, slash-resistant fabrics like Kevlar or other aramids. This layer protects the suit from the extreme temperature swings between direct sunlight (over 120°C or 250°F) and shadow (below -150°C or -240°F). It also provides the primary defense against impacts from tiny, high-velocity micrometeoroids or orbital debris, which could otherwise puncture the pressure bladder.

The Helmet and Visor Assembly

The Orlan’s helmet is not a separate piece that attaches with a neck ring. Instead, it is a large, “bubble-style” helmet that is permanently integrated into the hard upper torso. This design provides an exceptionally wide and unobstructed field of view, which is invaluable for situational awareness during an EVA.

The helmet is made of high-strength, impact-resistant polycarbonate. To protect the cosmonaut’s eyes from the unfiltered, blinding intensity of the sun, the helmet is equipped with two external visors. The first is a gold-tinted, vacuum-deposited sun visor. This reflective layer blocks the worst of the glare and a significant portion of harmful solar radiation. This visor can be raised or lowered by the cosmonaut as they move between sunlight and shadow.

A second, clear protective visor is layered on top of the sun visor. This outer shield acts as a “sacrificial” layer, absorbing any minor scratches or debris impacts and protecting the more critical sun visor and the helmet’s main pressure bubble. The helmet also features mounts for high-intensity lights and a wireless video camera , allowing ground controllers and crewmates to see what the spacewalker is seeing in real-time.

The Life Support Backpack (PLSS)

The rear-entry hatch is the Portable Life Support System (PLSS). This backpack is the suit’s engine room, containing all the consumables and machinery needed to keep the cosmonaut alive for up to seven hours, with reserves beyond that.

Key components inside the PLSS include:

• Oxygen Tanks: Redundant, high-pressure tanks provide 100% pure oxygen for breathing. The suit operates at a pressure of about 400 hectopascals (hPa), which is roughly 5.8 pounds per square inch(psi). This is about 40% of Earth’s sea-level atmospheric pressure.
• Ventilation System: A fan continuously circulates oxygen through the suit, pushing fresh oxygen into the helmet for breathing and drawing exhaled air away.
• Carbon Dioxide Scrubber: The exhaled air, rich in carbon dioxide (CO2), is passed through canisters containing lithium hydroxide or a similar chemical. This compound reacts with and “scrubs” the CO2, preventing it from building up to toxic levels.
• Cooling System: This includes the water pump that circulates water through the LCVG and the sublimator, which is the suit’s radiator. The warm water returning from the LCVG is fed to the sublimator, a device with a porous metal plate exposed to the vacuum. The water passes through the pores, instantly freezes, and then turns directly into gas (sublimes). This phase change very efficiently dumps the suit’s waste heat into space.
• Power: Lithium-ion batteries provide electricity for the suit’s fans, pumps, computer, radio, and lights.
• Radio and Telemetry: A communications system allows for two-way voice contact with the space station and ground control. This system also transmits a constant stream of telemetry, or health data, from the suit’s sensors back to Earth.

Gloves and Boots

The gloves are perhaps the most complex and critical “soft” part of any spacesuit. They must protect the cosmonaut’s hands from the vacuum while simultaneously allowing for the fine dexterity needed to handle tools, turn bolts, and clip tethers. Orlan gloves are custom-fitted to each cosmonaut and are replaceable. They are multi-layered, with an internal pressure bladder, a restraint layer, and an outer TMG. They often include integrated heaters to keep the fingertips from freezing in shadow.

The boots are more simple, as cosmonauts do not “walk” in space. They are primarily thermal and protective coverings for the feet, which are often used to anchor the cosmonaut into a foot restraint on the station’s exterior.

The “MKS” Enhancements

The Orlan-MKS is a significant technological leap over its predecessors, the Orlan-M and Orlan-MK. The “MKS” (Modernized, Computerized, Synthetic) designation is a direct reference to its three primary upgrades, which together increase the suit’s lifespan, improve its safety, and, most importantly, reduce the cosmonaut’s workload.

Computerized and Automated Thermal Control

The single most important enhancement is the fully automatic thermal control system.

In all previous Orlan models, managing body temperature was a manual task. The cosmonaut had a valve on their chest control panel that was, in effect, a faucet for the liquid cooling garment. If they were working hard and started to feel warm, they had to stop their task, reach over, and manually open the valve to increase the flow of cold water. If they stopped working and started to get cold, they had to remember to dial it back. This was a constant, distracting task that divided their attention.

The Orlan-MKS eliminates this. The suit is now “smart.” It uses sensors to monitor the cosmonaut’s vital signs and the suit’s internal environment. A new mini-computer system analyzes this data to estimate the cosmonaut’s metabolic rate – how hard they are working – in real-time. Based on this, the computer automatically adjusts the cooling water flow and temperature to keep the cosmonaut perfectly comfortable.

This automation is a massive improvement in human factors and efficiency. The cosmonaut is freed from “flying the suit” and can dedicate 100% of their mental energy to the complex EVA tasks at hand, such as repairing a module, installing new equipment, or deploying a satellite.

Synthetic and Modernized Materials

The “S” for “Synthetic” refers to the replacement of traditional rubber components with modern polyurethane. The main pressure bladders for the suit and gloves are now made from this advanced synthetic material.

Rubber, while flexible, has a limited lifespan. It degrades over time, becoming brittle and prone to micro-cracks, especially when exposed to the temperature cycles and radiation of space. This required frequent and costly suit replacements.

The new polyurethane bladders are far more durable, resilient, and resistant to this degradation. This change, combined with other modernized components, has extended the certified service life of the Orlan-MKS. While older models were rated for about 15 EVAs, the MKS is certified for up to 20 spacewalks over a five-year period. This extended lifespan reduces the number of new suits that must be launched to the space station, saving significant cargo mass and cost. The new material also makes the suit slightly lighter and more flexible.

Enhanced Diagnostics and Display

The Orlan-MKS inherits and improves upon the “computerized” aspect of the Orlan-MK. The suit’s control and data display is a chest-mounted unit with a prominent liquid-crystal display (LCD).

This computer system is the suit’s “dashboard.” It provides the cosmonaut with a clear, at-a-glance readout of all vital information:

• Suit pressure
• Oxygen levels
• Battery life
• CO2 levels
• Cooling system status

Beyond just displaying data, the computer actively monitors all systems for faults. If a primary system – like the main oxygen fan or water pump – begins to fail, the computer will automatically switch to the backup system and immediately alert the cosmonaut with a visual warning on the screen. It can provide simple diagnostic messages, telling the spacewalker what has failed and what system is now active. This “smart” diagnostic capability provides a level of situational awareness and safety that was impossible with older suits, which relied on simple warning tones or analog gauges.

Life Inside the Suit

A spacewalk in an Orlan-MKS is a physically and mentally demanding experience. The cosmonaut, sealed inside their personal spacecraft, is in a world of their own.

Pressure and Pre-Breathe

The International Space Station is pressurized to a normal sea-level atmosphere: 14.7 psi. The Orlan-MKS operates at a much lower pressure of 5.8 psi, using a pure oxygen atmosphere. This pressure differential is a critical operational factor.

A human cannot simply move from a 14.7 psi “mixed-gas” (nitrogen-oxygen) environment to a 5.8 psi pure-oxygen environment. Doing so would cause the nitrogen gas dissolved in their bloodstream to form bubbles as it comes out of solution, the same way carbon dioxide fizzes in a soda bottle when the cap is opened. This condition is known as decompression sickness , or “the bends,” and it is extremely painful and can be fatal.

To prevent this, cosmonauts must go through a “pre-breathe” protocol. Before an EVA, they spend a period of time breathing pure oxygen to purge the dissolved nitrogen from their bodies. A major advantage of the Orlan’s relatively high 5.8 psi operating pressure is that it requires a much shorter pre-breathe period compared to the American EMU, which operates at an even lower 4.3 psi. This makes the preparation for an Orlan-based EVA significantly faster and more efficient.

The Working Environment

Inside the suit, the cosmonaut hears the constant hum of the ventilation fan and the whir of the water pump. Their world is framed by the view out of their helmet. They communicate with their EVA partner and the station via the radio in their “Snoopy cap,” a cloth headset worn under the helmet.

Movement is difficult and exhausting. Every time the cosmonaut bends their arm or closes their hand, they are fighting against the 5.8 psi of pressure that is trying to keep the suit rigid. It is often described as trying to work while squeezing a very stiff balloon. Tasks that are simple on Earth, like turning a wrench, require immense and sustained effort, engaging muscles in the forearms, shoulders, and back. This is why spacewalkers must be in peak physical condition and why the LCVG is so essential to remove the massive amount of heat they generate.

Operations and Maintenance on the ISS

The Orlan-MKS suits are not personal equipment assigned to one cosmonaut. They are shared assets that belong to the Russian Orbital Segment of the ISS, stored in the airlock modules like Pirs (before its decommissioning) and Poisk.

A Multi-User Space Tool

The semi-rigid, adjustable-limb design allows a single suit to be used by multiple crew members of different sizes across many expeditions. Before a mission, a cosmonaut will be fitted for their suit on Earth, where the arm and leg lengths are precisely adjusted for their body. Once in space, they will use one of the several Orlan suits available on the station, which has likely been configured for them.

This reusability is a core part of the suit’s design. It is a robust, serviceable tool, much like any other piece of critical station hardware.

Servicing in Orbit

One of the most practical aspects of the Orlan family is its design for on-orbit maintenance. The suits were never intended to be returned to Earth for refurbishment. Cosmonauts are trained as their own spacesuit technicians.

After an EVA, the suit is mounted on a rack inside the airlock. The crew connects it to the station’s umbilical lines, which replenish its power and water supplies. The cosmonauts then perform a series of post-flight service tasks. They remove the spent lithium hydroxide canisters and replace them with fresh ones. They refill the oxygen tanks. They test all the systems to ensure they are ready for the next spacewalk.

The suit is also dried out. The internal humidity from breathing and sweating is removed to prevent mold and mildew from growing inside the suit’s layers. Because the suit’s components are modular and accessible, cosmonauts can even perform major part replacements in orbit , such as swapping out a faulty pump, fan, or battery, using a toolkit of spare parts kept on the station. This ability to service the suits entirely in space is a massive logistical benefit, eliminating the need to launch and return 110-kilogram (240-pound) suits.

Orlan-MKS Versus Its Contemporaries

The Orlan’s design philosophy is best highlighted by comparing it to its main counterparts: the American EMU and the Chinese Feitian suit.

Comparison with the NASA EMU

The NASA Extravehicular Mobility Unit (EMU) is the primary suit used by American and other international partner astronauts on the ISS. The differences are striking:

• Entry: The Orlan is a one-piece, rear-entry suit. The EMU is a two-piece, modular suit. The astronaut dons the “pants” (Lower Torso Assembly) and then slides up into the “shirt” (Hard Upper Torso), and the two halves are sealed together with a rigid waist ring. This process requires assistance.
• Sizing: The Orlan torso is one-size-fits-all, with adjustable soft limbs. The EMU is fully modular, with different-sized hard torsos, arms, and legs that can be assembled in various combinations to custom-fit a specific astronaut.
• Pressure: The Orlan operates at 5.8 psi, allowing for a short pre-breathe. The EMU operates at a lower 4.3 psi, which provides better mobility but requires a much longer and more complex nitrogen-purge protocol, sometimes including an overnight “campout” in the airlock at a lower pressure.
• Maintenance: The Orlan is designed to be fully maintained and serviced in orbit. The EMU, while having some on-orbit replaceable parts (like batteries and CO2 scrubbers), must be returned to Earth for major refurbishment and recertification.

Neither design is “better” than the other; they simply represent different solutions to the same set of problems, prioritizing different aspects of operations (e.g., Orlan prioritizes donning speed and on-orbit service, while the EMU prioritizes a custom fit and mobility).

Comparison with China’s Feitian Suit

The Chinese Feitian spacesuit , used by taikonauts for EVAs outside the Tiangong space station , is a direct testament to the success of the Orlan’s design. The Feitian is heavily based on the Orlan, developed from technology and suits Russia sold to China in the early 2000s.

Like the Orlan, the Feitian is a semi-rigid, rear-entry suit. While China’s engineers have since incorporated their own domestic technologies and modifications, the foundational design is unmistakably Orlan. This adoption by another major space-faring nation serves as a powerful validation of the rear-entry concept’s efficiency and reliability.

The Future of Orlan

The Orlan-MKS is the current workhorse for Roscosmos and is expected to remain in service for the entire operational life of the International Space Station. Its proven reliability and robust design make it an indispensable tool for station maintenance.

Looking ahead, Roscosmos has announced plans for a new, independent space station, the Russian Orbital Service Station (ROSS). This future station will require a fleet of reliable EVA suits for its assembly and maintenance. Given the decades of operational success and refinement, it is almost certain that the Orlan-MKS, or a direct successor based on its design, will be the suit of choice for the next generation of Russian cosmonauts. The legacy of the “sea eagle” – the translation of Orlan – is set to continue for decades to come.

Summary

The Orlan-MKS spacesuit is the pinnacle of a design philosophy that prioritizes reliability, efficiency, and on-orbit autonomy. Its unique semi-rigid, rear-entry design allows for rapid, unassisted donning, a significant operational advantage in space. The “MKS” upgrades – particularly the automatic thermal control system and durable synthetic bladders – have modernized this historic suit, reducing cosmonaut workload and extending its service life to 20 EVAs.

As a multi-user, on-orbit-serviceable asset, the Orlan is less a personal garment and more a permanent, reusable spacecraft in its own right. It has served as the workhorse for the Salyut , Mir , and International Space Station programs, and its design has even influenced the suits of other space-faring nations. The Orlan-MKS stands as a rugged, proven, and indispensable tool for humanity’s continued presence in orbit.