Right now, the International Space Station is the world’s highest construction site. But just how do you build something that is about 400 kilometres above the Earth and orbiting at approximately 28 000 km/h? The answer is “very carefully” – and one piece at a time.

Astronauts during a spacewalk

When

The “Canadarm2”

it is completed, the Space Station and its equipment will amount to about 455 tonnes. The American Space Shuttle, which is doing most of the Earth-to-space hauling, can only launch around 16 tonnes at a time to the Space Station’s orbit. Even the big Russian Proton booster that lifted the first ISS cargo in 1998 can lift only 20 tonnes. So the Space Station is built up by assembling parts or modules that connect together like a jigsaw puzzle.

It will take about 50 launches to bring all the Space Station's pieces into orbit – in exactly the right order, of course. Each new section must fit into those already in place. Every module has some kind of docking adaptor to allow it to fit precisely into another or to a node. In the beginning, most of the work was done by the robotic arm fitted in the Space Shuttle. Now, the Space Station has its own robotic arm, the Canadarm2. It is a bigger and more sophisticated robotic arm that helps enormously.