The International Space Station (ISS) marked its 25th anniversary in orbit this year, a testament to human ingenuity and international collaboration. Since its first assembly mission in December 1998, the orbiting laboratory has hosted over 270 spacewalks, evolving from construction marathons to critical maintenance operations. As the station ages, these extravehicular activities (EVAs) highlight the engineering feats and perils of sustaining a human presence in space.
Spacewalks, or EVAs, represent one of the most demanding aspects of ISS operations. Astronauts don pressurized suits to venture outside the station's protective hull, exposed to the vacuum of space, extreme temperatures, and micrometeoroid threats. The longest recorded EVA, clocking in at eight hours and 56 minutes, was performed by NASA astronauts Susan Helms and Jim Voss in 2001, as reported by BBC Future. This marathon involved relocating a docking port, a task requiring precise coordination amid zero gravity and limited visibility. Such durations push human limits, demanding suits with advanced life-support systems that recycle oxygen, regulate temperature, and manage waste—engineering principles rooted in balancing mobility with survival.
The Shift from Assembly to Upkeep
Early EVAs focused on piecing together the ISS's modular structure, a process akin to assembling a massive puzzle in orbit. Modules from the U.S., Russia, Europe, Japan, and Canada were launched separately and connected via robotic arms and human intervention. This modular design, a departure from monolithic stations like Russia's Mir, allowed for incremental expansion but introduced complexities in integration. Today, with assembly largely complete, spacewalks increasingly address wear and tear on solar panels, batteries, and cooling systems. Ageing components, battered by radiation and thermal cycling, necessitate replacements that can extend the station's operational life.
Why does this matter? The ISS's longevity underscores the viability of long-term space habitats, informing designs for future lunar bases or Mars missions. For instance, NASA's Artemis program draws lessons from ISS EVAs to develop suits with enhanced dexterity for dusty lunar regolith. Historically, the Mir station, operational from 1986 to 2001, saw similar maintenance EVAs, but its eventual deorbiting due to funding issues contrasts with the ISS's sustained international funding, now exceeding $150 billion. This comparison reveals how geopolitical cooperation can mitigate the financial burdens of space infrastructure.
Risks and Innovations in Extravehicular Activities
The inherent dangers of spacewalks were starkly illustrated in 2013 when Italian astronaut Luca Parmitano's helmet filled with water during an EVA, nearly drowning him in microgravity—a malfunction traced to a clogged cooling system, per BBC Future. This incident prompted redesigns in suit plumbing and emergency protocols, emphasizing redundancy in life-support engineering. Scientifically, EVAs enable hands-on experiments, like installing external payloads for Earth observation or astrophysics, yielding data on climate change and cosmic phenomena that ground-based telescopes can't match.
From an industry perspective, the ISS's EVA legacy influences the burgeoning commercial space sector. Private companies like SpaceX and Axiom Space are developing their own stations, where spacewalks will be essential for construction and repairs. Even billionaires venturing to space must endure rigorous training, highlighting how EVAs democratize yet professionalize access to orbit. As the ISS approaches potential decommissioning in the 2030s, transitioning to commercial platforms will rely on these hard-won lessons, potentially reducing costs through reusable suit technologies and AI-assisted robotics.
In essence, 25 years of ISS spacewalks encapsulate the blend of triumph and tribulation in human spaceflight. They not only maintain a vital research outpost but also pave the way for deeper space exploration, where engineering resilience meets scientific curiosity.