The Space Shuttle era was characterized by the emergence of  the first reusable spacecraft along with humanity building the largest structure ever outside our atmosphere, the International Space Station. It was an era of incredible achievement. Collectively, the shuttles Enterprise, Columbia, Challenger, Discovery, Endeavor, and Atlantis orbited the earth 21,152 times and covered 542,398,878 miles. Astronauts from 16 different nations have flown on shuttle missions. Dr. David Williams is one of them.