It has been over six years since I last floated in zero gravity through the tunnel that connects the space shuttle to the International Space Station. I visited this orbiting laboratory on four occasions between 2001 and 2011.
Every time I approached the station, I was in awe of its complexity and its beauty. But more than anything, I was in awe of the fact that we had the nerve to even attempt to build something of this magnitude.
It was the United States that led the international coalition of 16 nations to build the space station. Constructing this outpost in outer space took dozens of missions spanning well over a decade to complete, and considerable money. It is clearly one of the more complicated engineering projects humans have undertaken.