Building the International Space Station: What Flew, What Was Cancelled and What Comes Next

The station itself: a modular outpost in low Earth orbit, first launched in November 1998 and jointly operated by NASA, Roscosmos, the European Space Agency, JAXA and the Canadian Space Agency. It has been continuously crewed since November 2000 and is expected to remain operational through 2030.

A flown supply container. These pressurized modules rode in the Space Shuttle cargo bay and were berthed first to Unity and later to Harmony. Three were built, Leonardo, Raffaello and Donatello, by Alenia Aeronautica for the Italian Space Agency, and the first flight was in March 2001.

A flown laboratory rack inside the Columbus module. Biolab supports research on small plants, small invertebrates, microorganisms, animal cells and tissue cultures, and its incubator has centrifuges that apply controlled levels of acceleration.

A flown robot arm. Launched in July 2021 on a Proton rocket alongside the Nauka module, it was the first robotic arm able to work on the Russian segment, supplementing the Strela cargo cranes.

A flown helper. Int-Ball is a series of autonomous, self-propelled ball cameras working inside the Japanese Kibo module to photograph and film, which reduces the workload on the crew. Two different Int-Ball cameras had been delivered by May 2024.

The first cancellation. Planned as the main living quarters, roughly the size of a bus, with a galley, toilet, shower, sleeping quarters and medical facilities, its pressurized hull was finished before the module was cancelled. It would have attached to the Tranquility module.

A cancelled science element. Its most significant planned capability was a 2.5 meter centrifuge that would have let researchers study the effects of varying levels of artificial gravity on biological specimens.

A cancelled safety net. It was proposed as a backup for the Zvezda Service Module and Progress spacecraft, to keep the station at altitude, perform reboosts and debris avoidance maneuvers and supply attitude control and propellant. The Interim Control Module would have covered the first three years.

A planned Russian element. It was first meant to fly on a Proton or Zenit rocket, but its launch was later moved to the Space Shuttle as part of a tradeoff agreement covering other station elements.

A proposed docking module, also called the Docking Hub System. In 2010 NASA was considering a forty month design and development effort that would have led to a launch in late 2013.

A cancelled ferry. The Crew Space Transportation System, first called the Advanced Crew Transportation System, was a joint European Space Agency and Russian design meant to service the station and support exploration of the Moon and beyond. It was shut down when the conference allocated no further funding.

The planned successor in spirit: a modular station to be built and operated by India, planned at fifty two tonnes in an orbit of about four hundred kilometres. Its completion slipped from 2030 to 2035, with the first module expected on an LVM3 launch vehicle.