Pressurized space gloves can cause astronauts to lose their fingernails
Spacewalks are notoriously brutal on hands. Inside a spacesuit, gloves must be highly pressurized to protect astronauts from the vacuum. When astronauts bend their fingers, the rigid gloves resist, placing extreme, constant pressure on their fingertips. This frequent chafing and squeezed circulation often leads to a painful condition called fingernail delamination, where nails completely detach from the nail bed.
The Pressure Vessel on the Hand
A spacesuit is not merely a heavy garment; it is a self-contained, human-shaped spacecraft designed to sustain life in the lethal environment of space. To protect an astronaut from the vacuum outside, the suit must maintain an internal gas pressure. However, this pressure difference causes the flexible materials of the suit to balloon outward and stiffen. Any attempt to bend a joint in a pressurized suit requires physical effort to deform the inflated volume against the internal gas.
While large joints like elbows and knees can be equipped with mechanical bearings and fabric convolutes that keep the joint volume constant when bending, the human hand presents a much steeper engineering challenge. Hands contain dozens of small bones, joints, and delicate skin surfaces that move across multiple axes simultaneously. When enclosed inside a pressurized glove, every single finger movement becomes a battle against the outward push of the suit atmosphere, which constantly forces the glove back into an open, relaxed posture.
The Biomechanics of Working in a Vacuum
During extravehicular activity (EVA), astronauts are required to perform complex mechanical tasks for six to eight hours at a time. They install structural hardware, manipulate electrical connectors, open access panels, and grip safety tethers. Every time an astronaut closes their fingers around a tool or handrail, their forearm and hand muscles must continuously fight against the rigidity of the pressurized glove. This continuous exertion is comparable to squeezing a heavy resistance spring for hours without rest.
This constant strain fundamentally alters how mechanical forces act upon the fingertips. Because the pressurized glove cannot flex in exact unison with human joints, the finger slides within the glove pocket during flexion. The tip of the finger is driven forcefully against the rigid inner cap of the glove. Over thousands of repetitive grip cycles during a single spacewalk, the fingertips absorb sustained focal pressure and intense shear stress.
The Mechanism of Fingernail Delamination
The direct physiological outcome of this sustained impact and friction is a condition known as fingernail delamination, or onycholysis. As the fingertip repeatedly collides with the inner surface of the glove, the focal pressure compromises microcirculation in the capillary bed beneath the nail. The combination of restricted blood flow and relentless mechanical shearing gradually tears the connection between the nail plate and the underlying nail bed.
Astronauts frequently return from spacewalks with extensive blistering, abrasions, and subungual hematomas, where blood pools beneath the fingernails. In severe cases, the sustained trauma causes the fingernail to detach completely from the digit, either during the mission or in the weeks following the spacewalk. This form of hand trauma is recognized as one of the most common occupational injuries associated with extravehicular operations.
The Layered Architecture of Space Gloves
The vulnerability of the hand is partly a consequence of how space gloves must be constructed to ensure survival. An EVA glove is composed of multiple distinct layers. The core contains a gas-retaining pressure bladder, typically surrounded by a structural restraint layer that prevents the bladder from ballooning out of shape. Outside of this pressure core sit multiple layers of thermal insulation and an abrasion-resistant outer shell designed to guard against micrometeoroids and sharp hardware edges.
Each added layer compounds glove stiffness and degrades tactile feedback. To restore some degree of usability, glove designs incorporate textured palm materials and silicone fingertip caps that provide traction against smooth metals. However, the physical thickness of this multi-layer sandwich prevents the glove from bending naturally at the knuckles, concentrating mechanical resistance directly onto the distal joints and fingertips.
Thermal Extremes and Circulatory Compromise
The thermal conditions of low Earth orbit further exacerbate the mechanical stresses placed on an astronaut's hands. As a spacecraft passes between direct sunlight and the shadow of Earth, external temperatures swing dramatically by hundreds of degrees. While the torso is cooled by a liquid cooling garment, the extremities are prone to extreme heat loss whenever an astronaut grasps cold metal structures in shadow.
When hands get cold, blood vessels in the extremities constrict, reducing tissue compliance and making the nail bed significantly more vulnerable to pressure damage. To prevent frostbite and maintain dexterity, space gloves integrate fingertip heating elements. Yet balancing thermal regulation, perspiration, and mechanical friction remains difficult, as sweating inside the glove can soften the skin and increase the likelihood of blistering and tissue separation under pressure.
Design Adaptations and Future Concepts
Mitigating hand trauma relies heavily on precision tailoring. Astronauts undergo detailed 3D scanning and plaster casting of their hands to produce custom-sized inner glove liners and fingertip caps. Even a discrepancy of a few millimeters in glove finger length can dramatically increase pressure on the nail bed, making custom fabrication and individualized fit checks essential prior to flight.
Beyond refining traditional gas-pressurized gloves, engineers have explored alternative designs such as mechanical counterpressure (MCP). Instead of using gas to pressurize the hand, MCP concepts use form-fitting, elastic fabrics to exert direct mechanical force on the skin. While engineering a practical, leak-free counterpressure system presents immense hurdles, the search for glove designs that preserve human dexterity without damaging tissue remains central to spacesuit development.
Key takeaways
•Internal spacesuit pressure makes glove fingers naturally stiffen and resist bending, forcing astronauts to overcome continuous mechanical resistance during spacewalks.
•Repetitive grip cycles drive the fingertips against the inner glove caps, generating shear forces and restricting blood flow until fingernails detach from the nail bed.
•Space gloves require multiple bulky layers for gas retention, thermal insulation, and micrometeoroid protection, which inherently compromises natural hand articulation.
•Custom sizing based on 3D hand scans and integrated thermal heating elements are critical engineering measures used to minimize hand trauma.