Cosmonauts Day (3)

5k Konstantin E. Tsiolkovsky 1857-1935), aerodynamics innovator, and futuristic space station.
10k, Sergei P. Korolev (1906-1966), rocket scientist, and Vostok spaceship
15k, Yuri Gagarin, 1st cosmonaut, Sputnik I and Vega probe.
Se-tenant Vostok and inscribed first space flight.