Professor Hawking was not constricted to his wheelchair but laid flat so that he floated in the air with the assistance of a nurse.
"It was amazing. The zero-g part was wonderful," he said. "I could have gone on and on – space here I come!
"The [Nasa] space shuttle landing facility is the first step to the moon and Mars. It is very special for me, to fly into weightlessness from here."
Dr Peter Diamandis, chief executive of Zero-G, the company which runs the flights, said that Professor Hawking displayed "grins of sheer joy and excitement".
Other tickets for the flight were given to a number of charities to auction off; in total $144,000 (£72,000) was raised and people who bought the tickets were also treated to a dinner and lecture by Professor Hawking.
His books A Brief History of Time and Black Holes and Baby Universes and Other Essays explore the basic laws, history and future of the universe.
Last November he was honoured with the prestigious Copley medal from the Royal Society for his "astonishing" contribution to theoretical physics and cosmology.
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