A graduate of Hanyoung Foreign Language High School, Ko studied mathematics and cognitive science at Seoul National University.

He won a bronze medal at a national amateur boxing tournament in 2004 and climbed a 7,546-meter high mountain in China's Xinjiang Province, Muztagh Ata, the same year.

On September 5, 2007, the Korean Ministry of Science and Technology chose Ko San over Yi So-Yeon based on performance in tests during training in Russia.

[1][2] However, on March 10, 2008, this decision was reversed, after the Russian Federal Space Agency asked for a replacement because Ko apparently violated security protocol for maintaining secret information twice at the Yuri Gagarin Cosmonaut Training Center.

Now he is taking a leave of absence from the John F. Kennedy School of Government to run an NGO, TIDE Institute, which he founded in February 2011.