Greatest machine ever built: Astronaut on ISS turning 20
German astronaut and current ISS commander Alexander Gerst, on International Space Station's 20th anniversary, said, "I feel privileged to serve on the greatest machine ever built." Russian-built Zarya, the first ISS module, was launched on November 20, 1998. ISS flies approximately 400 kilometres above Earth and circles the globe once every 90 minutes at a speed of around 28,000 kmph. 