The new additions to the ISS will include a crew habitat that will serve as a home for future space tourists.
It will also have a research and manufacturing facility and large-windowed Earth observatory, according to Axiom, the Texas-based company that is building the extension.
Axiom hopes the segment could one day serve as a self-contained space station that could replace the ISS when it is decommissioned.
It hopes to launch the new commercial hub in 2024, it said.
Nasa announced last year that it would allow space tourists onto the ISS, as part of a broader effort to encourage commercial companies to become involved in US space exploration. Those first visitors were expected to arrive later this year.
Adding new segments to the ISS could allow more people to travel to the station by increasing the volume, Axiom said, as well as leaving space for new kinds of research "such as isolation studies and Earth observation".
Over time, Axiom hopes that the work currently being done on the International Space Station is gradually transferred to its new private segment, allowing for it to continue without interruption when the ISS is retired.
At that point it will be able to detach and serve as a self-contained space station. At that point, Nasa will no longer have to pay for the cost of running the ISS or launching a replacement, Axiom suggested.
In 2018, Axiom commissioned designer Philippe Starck to create interiors for the habitation module of a possible space station. He described the result as a "comfortable and friendly egg".
"Starck’s vision was to create a nest, a comfortable and friendly egg, which would feature materials and colors stemmed from a fetal universe," a press release at the time said. "The walls are sprinkled with hundreds of nano-Leds with changing colors as a continuation to the view on the universe through the large windows.
"Just as all the shades of lights and colors of day and night, the egg will also live to the mood and biorhythm of its osmotic inhabitant."
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