Space Stations Compared: ISS, Tiangong, and the Commercial Stations Coming Next

For the first time in history, multiple crewed space stations are operating simultaneously in orbit—and several more are being built. The International Space Station, humanity's flagship outpost for over two decades, is approaching the end of its operational life. China's Tiangong station is fully assembled and hosting a continuous stream of crew rotations. And at least four commercial stations are racing through development, each promising to reshape how humanity lives and works in space. The ISS era is ending, but a new age of commercial stations is just beginning.

ISS: The Gold Standard

The International Space Station remains the largest and most complex structure ever assembled in orbit. Stretching 109 meters from end to end—roughly the length of an American football field—and spanning 73 meters across its solar array truss, the ISS is visible to the naked eye from the ground on clear nights. It has a total pressurized volume of about 916 cubic meters, providing enough habitable space for a crew of six to seven astronauts to live and work continuously.

The station's mass is staggering: approximately 420,000 kilograms, assembled piece by piece across more than 40 missions between 1998 and 2011. Sixteen partner nations contributed modules, hardware, and crew through five space agencies—NASA, Roscosmos, ESA, JAXA, and CSA. The total investment exceeds $150 billion, making the ISS the most expensive single object ever constructed by human civilization.

Since November 2, 2000, humans have lived aboard the ISS without interruption. That streak of continuous occupation has lasted more than 24 years, spanning dozens of crew rotations and hundreds of individual astronauts and cosmonauts from countries around the world. Over that period, more than 3,000 scientific experiments have been conducted aboard the station, spanning fields from fundamental physics and materials science to human physiology, biology, Earth observation, and technology demonstration.

Key research achievements include studies of bone and muscle loss in microgravity that have informed treatments for osteoporosis on Earth, protein crystal growth experiments that accelerated pharmaceutical development, combustion science that improved fuel efficiency, and the Cold Atom Laboratory that created the coldest known spot in the universe to probe quantum mechanics. The ISS also served as a proving ground for technologies critical to deep-space exploration, from life support systems to radiation shielding.

NASA has extended ISS operations through 2030, giving commercial stations time to come online before the outpost is retired. When that day comes, the station will not simply be abandoned. SpaceX holds a $843 million contract to develop a dedicated deorbit vehicle—a modified Dragon spacecraft that will guide the station through a controlled reentry over an unpopulated stretch of the South Pacific Ocean, ensuring the massive structure does not pose a risk to anyone on the ground.

China's Tiangong: A New Permanent Presence

China's Tiangong space station, whose name translates to "Heavenly Palace," represents a remarkable achievement for China's crewed spaceflight program. Completed in late 2022 with the addition of two laboratory modules, Tiangong is the world's second permanently crewed orbital outpost and the only one built entirely by a single nation since the Soviet Union's Mir station.

The station has a distinctive T-shaped configuration. At its center is the Tianhe core module, launched in April 2021, which provides living quarters, life support, guidance, navigation, and propulsion. Attached to either side are two experiment modules: Wentian, launched in July 2022, which carries biology and life science research facilities plus a backup airlock, and Mengtian, launched in October 2022, which hosts physics, fluid mechanics, and materials science payloads along with an exposed experiment platform for space-environment research.

Together, the three modules provide approximately 110 cubic meters of habitable volume—significantly less than the ISS but carefully optimized for efficiency. The station supports a permanent crew of three taikonauts, expanding to six during crew rotation periods when incoming and outgoing teams overlap for roughly one week. Shenzhou crew capsules and Tianzhou cargo vehicles ferry personnel and supplies, all launched on China's Long March rockets.

China built Tiangong partly because of political necessity. The Wolf Amendment, passed by the United States Congress in 2011, prohibits NASA from cooperating with China's space agencies using federal funds. Effectively excluded from the ISS partnership, China pursued its own path. The result is an entirely indigenous capability: Chinese-designed modules, Chinese launch vehicles, Chinese spacesuits, and Chinese mission control. The station has been continuously crewed since June 2022, and its experiment portfolio is growing rapidly, with hundreds of experiments planned or underway across dozens of scientific disciplines.

China has announced plans to expand Tiangong from three to six modules in the coming years, roughly doubling its capability. International collaboration is part of that vision—China has signed agreements with the United Nations Office for Outer Space Affairs to host experiments from developing nations, and discussions with several countries about crew visits are underway.

ISS vs. Tiangong: A Direct Comparison

Comparing the ISS and Tiangong head-to-head reveals how different these two stations are in scale, approach, and philosophy, even as they both serve as orbital laboratories for human habitation.

• Mass: ISS weighs approximately 420,000 kg across its many modules and truss segments. Tiangong comes in at roughly 66,000 kg—about one-sixth the mass. The ISS is by far the larger structure.
• Habitable volume: ISS offers approximately 916 cubic meters of pressurized space versus Tiangong's 110 cubic meters. The difference is roughly ninefold, reflecting the ISS's decades of modular expansion.
• Crew size: ISS typically hosts 6 to 7 crew members at a time, with surges during crew handovers. Tiangong supports 3 crew members, surging to 6 during rotations.
• Modules: ISS consists of 16 pressurized modules contributed by multiple nations. Tiangong has 3 modules (expanding to 6), all built by China.
• International partners: ISS brings together 16 nations through 5 space agencies. Tiangong is primarily Chinese, with limited international experiments through UN agreements.
• Orbital inclination: ISS orbits at 51.6 degrees, a compromise that allows access from both U.S. and Russian launch sites. Tiangong orbits at 41.5 degrees, optimized for Chinese launch facilities.
• Assembly date: ISS assembly began in 1998 and continued through 2011. Tiangong was assembled from 2021 to 2022, using modern technology and lessons learned from decades of spaceflight.
• Research volume: ISS has hosted more than 3,000 experiments over 24+ years. Tiangong's experiment portfolio is growing but still numbers in the hundreds, reflecting its much shorter operational history.
• Cost: ISS total investment exceeds $150 billion across all partners. Tiangong's cost has not been officially disclosed but is estimated to be a fraction of the ISS figure, reflecting both lower labor costs and a simpler architecture.

The bottom line: Tiangong is newer, more modern in certain subsystems, and entirely self-sufficient, but the ISS remains vastly larger, more capable, and more internationally diverse. Both demonstrate that continuous human presence in low Earth orbit is achievable, setting the stage for the commercial stations that will follow.

Axiom Station: Building on the ISS Foundation

Axiom Space is taking the most incremental—and arguably the least risky—approach to building a commercial space station. Rather than launching a stand-alone outpost from scratch, Axiom will begin by attaching commercial modules directly to the ISS, leveraging the existing station's life support, power, and communication infrastructure during the initial operational phase. Once several modules are in place and fully checked out, the Axiom segment will detach from the ISS to become an independent free-flying station.

The first module, Axiom Habitat 1 (Hab 1), is targeting a launch around 2026. It will attach to the ISS's forward port on the Harmony node, providing additional crew quarters, research space, and an Earth-observation cupola. Subsequent modules—Hab 2, a research and manufacturing facility, and a power and thermal module—will follow on a phased schedule, gradually building out the Axiom segment before it separates into an independent station.

Axiom has not waited for its station to generate revenue. The company has already flown four private astronaut missions to the ISS—Ax-1 through Ax-4—demonstrating demand for commercial crew flights and establishing relationships with national space programs, researchers, and private customers. These missions have carried astronauts from Saudi Arabia, Turkey, Italy, Poland, Hungary, India, and other countries, signaling the breadth of potential customers for the future station.

Leading the effort is Michael Suffredini, who served as NASA's ISS Program Manager for a decade. His intimate knowledge of station operations, technical requirements, and international partnerships gives Axiom a significant advantage in navigating the complexities of building and operating a crewed orbital facility. The company's target markets include government research, private-sector R&D, in-space manufacturing, national astronaut programs, and premium space tourism.

Vast Haven-1: The Startup Approach to Space Stations

Vast is betting that speed and simplicity can win the commercial station race. Haven-1 is designed as a single-module station that can launch fully assembled on a SpaceX Falcon 9 rocket—no orbital assembly required. The module will include crew quarters for four astronauts, research facilities, and large Earth-facing windows, all packed into a compact but functional spacecraft.

The company is targeting a 2025–2026 launch for Haven-1, which would make it one of the first commercial stations to reach orbit. SpaceX Crew Dragon capsules will ferry astronauts to and from the station, using the same proven vehicle that already carries NASA crews to the ISS. The initial missions will be relatively short-duration, but Vast plans to extend occupation periods as systems mature and confidence grows.

Haven-1 is explicitly designed as a stepping stone. Vast's longer-term vision centers on Haven-2, a significantly larger station that would launch on SpaceX's Starship super heavy-lift vehicle. Haven-2 is expected to incorporate artificial gravity capabilities—a long-sought technology that could revolutionize long-duration spaceflight by reducing the bone loss, muscle atrophy, and fluid shifts that plague crew members in microgravity.

Vast was founded by Jed McCaleb, the cryptocurrency entrepreneur behind Stellar and co-founder of Ripple, and has connections to the Polaris program through Jared Isaacman's broader commercial spaceflight efforts. The company embodies the Silicon Valley approach to space infrastructure: move fast, launch early with minimal viable hardware, iterate based on real operational data, and scale aggressively once the concept is proven.

Blue Origin Orbital Reef: A Business Park in Space

Blue Origin and Sierra Space have teamed up to develop Orbital Reef, a concept they describe as a "mixed-use business park in space." Selected by NASA under the Commercial LEO Destinations (CLD) program, Orbital Reef is designed from the ground up to accommodate a diverse range of customers and activities under one orbital roof.

The station architecture reflects this multi-tenant philosophy. Blue Origin is responsible for the core module, which provides propulsion, attitude control, power distribution, and primary life support. Sierra Space contributes the LIFE (Large Integrated Flexible Environment) habitat, an expandable module that launches in a compact configuration aboard a rocket and then inflates in orbit to provide a large pressurized volume—far more interior space per launch mass than a traditional rigid module.

When fully assembled, Orbital Reef is designed to support approximately 10 crew members simultaneously, making it one of the larger commercial stations under development. Planned facilities include dedicated research laboratories, microgravity manufacturing bays, crew quarters designed for comfort on longer stays, and modules configured specifically for space tourism with premium viewing areas.

The station is expected to launch on Blue Origin's New Glenn rocket, which provides heavy-lift capability tailored to the station's module sizes. Sierra Space is also developing the Dream Chaser spaceplane, a winged vehicle that lands on conventional runways and can serve as a logistics vehicle for the station, delivering cargo and potentially returning manufactured goods to Earth with gentle runway landings rather than ocean splashdowns.

Target markets for Orbital Reef include government research (NASA as anchor tenant), pharmaceutical and biotech companies conducting microgravity R&D, materials science and manufacturing firms, media and entertainment companies (including film production in orbit), national space programs seeking crew training and flight experience, and premium tourism operators. The business park metaphor is deliberate: just as commercial real estate provides flexible space for diverse tenants on the ground, Orbital Reef aims to provide flexible orbital volume for diverse customers in space.

Starlab: European Expertise Meets American Ambition

Starlab, developed by Voyager Space in partnership with Airbus, brings European aerospace manufacturing expertise to the commercial station race. Selected alongside Orbital Reef under NASA's CLD program, Starlab takes a distinctive single-large-module approach: rather than assembling multiple smaller modules in orbit, the station would launch as one integrated structure on a SpaceX Starship, fully outfitted and ready for occupation.

The single-module architecture offers both advantages and constraints. On the plus side, it eliminates the complexity and risk of orbital assembly, reduces the number of launches required, and allows extensive ground testing of the complete integrated system. The trade-off is that the station's ultimate size is limited by what can fit inside Starship's payload fairing, though that is still a very large volume by historical standards.

Airbus brings decades of experience building European ISS modules, including the Columbus laboratory, as well as satellite and spacecraft manufacturing at industrial scale. The company's involvement gives Starlab strong international credibility and a natural pathway to European and international customers.

Starlab's concept includes what the team has dubbed the "George Washington Carver Science Park," a dedicated research platform optimized for continuous scientific experimentation. The vision extends beyond traditional space agency research to include commercial pharmaceutical development, advanced materials processing, and Earth observation services. International partnerships are a core part of the strategy, with multiple national space agencies already in discussions about utilization agreements. The station is targeting a launch in the late 2020s, aiming to be operational before the ISS retires.

Lunar Gateway: An Outpost Beyond LEO

While not a low Earth orbit station, NASA's Lunar Gateway deserves mention in any comprehensive survey of space stations because it represents the next evolution of orbital habitation. Gateway will be a small station in near-rectilinear halo orbit (NRHO) around the Moon, serving as a staging point for Artemis lunar surface missions and a platform for cislunar science.

The initial configuration consists of two modules: the Power and Propulsion Element (PPE), which provides solar electric propulsion and communications, and the Habitation and Logistics Outpost (HALO), which supplies minimal living quarters and docking ports. Unlike the ISS, Gateway will not be permanently crewed—astronauts will visit for weeks at a time during Artemis missions, with the station operating autonomously between visits.

Gateway is an international endeavor. NASA leads, with major contributions from ESA (the ESPRIT refueling module and I-Hab habitation module), JAXA (life support and logistics), and CSA (the Canadarm3 robotic system). The PPE and HALO modules will launch together on a SpaceX Falcon Heavy rocket, with additional modules following on subsequent launches.

Gateway's significance extends beyond its immediate role in Artemis. It establishes a permanent human-tended facility in deep space for the first time, demonstrates technologies for long-duration operations far from Earth, and serves as a proving ground for systems needed for eventual Mars missions. Its modular, international approach echoes the ISS model while pushing farther from Earth than any previous station.

What Commercial Stations Will Do Differently

The shift from the ISS to commercial stations represents more than a change of ownership—it is a fundamental rethinking of why space stations exist and how they operate. The ISS was designed primarily as a research laboratory and diplomatic partnership. Commercial stations are being designed as businesses.

The for-profit model means station operators will sell time, volume, and services to paying customers rather than allocating resources through government agreements. This approach creates incentives for efficiency, customer service, and cost reduction that were largely absent in the ISS model. If a station cannot attract and retain customers, it fails—a powerful motivator.

Microgravity manufacturing is expected to be one of the most significant commercial applications. Several products have already been demonstrated on the ISS that are superior when produced in the absence of gravity. ZBLAN fiber optic cable manufactured in microgravity has dramatically lower signal loss than its terrestrial equivalent, with potential applications in telecommunications and medical imaging. Pharmaceutical companies have used microgravity to grow more perfect protein crystals, accelerating drug development. Advanced alloys and semiconductor materials that cannot be produced on Earth due to density-driven convection have been successfully made in orbit.

Tourism will be another major revenue stream. The ISS has hosted a handful of private visitors at costs exceeding $50 million per seat, but commercial stations will be designed from the start with tourism in mind—better viewing windows, more comfortable accommodations, and more capacity. Media production is a related market: the first feature films partially shot in space have already attracted enormous public interest, and purpose-built stations could serve as orbital sound stages.

Perhaps the most transformative customer segment is national space programs. Dozens of countries want their own astronauts in space but cannot afford to build their own stations or even their own crew vehicles. Commercial stations can offer turnkey solutions: buy a seat on a crew vehicle, rent laboratory space, receive training and mission support, and fly your national astronaut on a mission—all from a single commercial provider. This democratization of access could dramatically expand the number of nations with direct human spaceflight experience.

The ISS Transition Challenge

The central risk of the coming decade in human spaceflight is the transition gap. The ISS is scheduled to retire around 2030. Commercial stations need to be operational before then. If commercial stations are delayed—and major space programs are rarely on schedule—the United States could face a period without any American space station in orbit for the first time since 2000.

NASA has structured its approach to mitigate this risk by funding multiple commercial station programs simultaneously, ensuring that even if one or two programs fall behind, at least one station should be ready in time. The agency plans to serve as an anchor tenant on commercial stations, purchasing a guaranteed minimum of astronaut time and research capacity to provide revenue certainty for station operators.

The shift from owner to customer requires a fundamental change in NASA's institutional culture. For decades, NASA has designed, built, and operated its own crewed vehicles and stations. Under the commercial model, NASA specifies requirements and purchases services, much as it now buys crew transportation from SpaceX rather than operating its own crew vehicle. This approach proved successful in the Commercial Crew Program, but scaling it to an entire space station—the most complex crewed facility ever operated—is a much larger challenge.

Knowledge transfer from ISS operations to commercial station teams is critical. More than two decades of hard-won experience in life support, thermal management, radiation protection, crew health, resupply logistics, and emergency procedures must be passed from NASA's ISS teams to the commercial operators who will build and run the next generation of stations. Several commercial station leaders, including Axiom's Suffredini, come from the ISS program, which helps, but institutional knowledge extends far beyond any individual.

The ISS deorbit itself is a massive engineering challenge. At 420,000 kg, the station is by far the largest object ever intentionally deorbited. SpaceX's deorbit vehicle must execute a precisely controlled reentry, targeting the South Pacific Ocean Uninhabited Area (also known as the spacecraft cemetery) to avoid any risk to populated areas. The consequences of an uncontrolled reentry of a 420-ton structure are severe, making this one of the most critical operations in the history of spaceflight.

The Future: A Multi-Station World

If current plans hold, the 2030s will see an unprecedented proliferation of crewed orbital facilities. China's Tiangong will likely be expanded to six modules and operating at full capacity. Axiom Station will be free-flying independently, potentially with multiple attached modules serving diverse customers. Orbital Reef and Starlab should be operational, each serving their own mix of government, commercial, and international clients. Vast may have progressed from Haven-1 to the much larger Haven-2, potentially incorporating artificial gravity. Lunar Gateway will be supporting Artemis surface missions from its perch in lunar orbit.

This means that by the mid-2030s, four to six crewed stations could be operating simultaneously—more than at any time in history. The competitive pressure among station operators will drive innovation in services, reduce costs through efficiency gains, and create a genuine market for orbital access that goes far beyond what any government program could achieve alone.

The implications run deep. When multiple stations compete for customers, access to space becomes driven by market economics rather than government budgets. Prices fall. Services improve. New applications emerge that no one anticipated, just as the internet enabled business models that the original ARPANET designers never imagined. Space shifts from being an exclusive club of wealthy nations and elite astronauts to an accessible destination for researchers, entrepreneurs, tourists, manufacturers, and students.

There will be setbacks. Stations will face technical problems, funding shortfalls, schedule delays, and the inherent dangers of operating complex systems in the vacuum of space. Not every commercial station program currently in development will succeed. But the direction is clear: humanity is moving from a world with one aging space station to a world with many, from government monopoly to commercial competition, from a single international partnership to a diverse ecosystem of orbital platforms serving customers that the ISS architects never envisioned.

The ISS proved that humans can live and work in space continuously. The commercial stations coming next will prove that space is not just a destination for government explorers but a place where ordinary economic activity—manufacturing, research, tourism, and commerce—can thrive. That transition, more than any single rocket launch or Moon landing, may ultimately be remembered as the moment humanity truly became a spacefaring civilization.