ORLANDO, Fla. _ The International Space Station has turned 20 years old.
Construction for the orbiting marvel began with the launch of the Zarya Functional Cargo Block from Kazakhstan on Nov. 20, 1998.
The temporary control module for the ISS took off from the Baikonur Cosmodrome, the cargo of a Proton rocket. It was the building block for many modules to come, including the Unity node that brought up just two weeks later on STS-88 by the crew of Space Shuttle Endeavour.
While Zarya was launched by the Russian Space Agency, it was built by Boeing and the agency. Unity's mating with Zarya was the first of many missions for what is now a structure with a 240-foot-long pressurized module, 357.5-foot-long truss and 239.4-foot-long solar array that weighs 925,335 pounds with a habitable space of 13,696 cubic feet.
The current structure, or at least the major components of it, comes courtesy of 42 assembly missions, 37 of them from the space shuttle program.
The space station hosts a six-person crew and has had more than 230 individuals from 18 countries on board. It has been continuously occupied since November 2000.
Astronaut Peggy Whitson lived there the longest at 665 days.
It has also hosted more than 2,500 scientific experiments from more than 100 countries.
The station orbits the on average 240 miles above the Earth once every 90 minutes or so at 5 miles per second.
After 20 years, that's more than 116,000 orbits and more than 2.9 billion miles traveled.
