NASA astronaut Tim Kopra, Commander of Expedition 47, floats inside the Russian segment on Cosmonautics Day 2016. Behind him are photographs (left to right) of Konstantin Tsiolkovsky, a Russian rocket scientist and pioneer of rocketry and astronautics, Sergei Korolev, the lead Soviet rocket and spacecraft engineer during the Space Race, Yuri Gagarin, the first human to fly in outer space, and a photo of Gagarin and Korolev together. Apr. 12, 2016 marked the 55th anniversary of Gagarin's flight.