Space stations were initially envisioned by scientists and science fiction writers as great wheels in the sky inhabited by dozens of crew members studying Earth from afar, conducting scientific research, and eventually building interplanetary spacecraft that would take explorers to the moon, to Mars, and beyond. These orbital outposts would slowly spin like giant centrifuges to provide Earthnormal gravity to their inhabitants and set the stage for permanent colonies in space.

While this is certainly possible in the future, the space station we have today is much more modest by comparison. The International Space Station (ISS) is of the same basic design pioneered by the world's first space station, Salyut-1, which was launched by the Soviet Union in 1971. Salyut-1 and all the other stations that have followed, including the current ISS, are modular in nature, more like mobile homes in...