1. Yuri Kondratyuk was a pioneer of astronautics and spaceflight, a theoretician and a visionary who, in the early 20th century, developed the first known lunar orbit rendezvous, a key concept for landing and return spaceflight from Earth to the Moon.
Yuri Kondratyuk was born as Aleksandr Ignatyevich Shargei in 1897 in Poltava, Russian Empire, although his family originally lived in Kiev.
Yuri Kondratyuk's father, Ignat Benediktovich Shargei, was a Jewish convert to Catholicism who studied physics and mathematics at St Vladimir Imperial University of Kiev at the time of his marriage.
From an early age, Yuri Kondratyuk demonstrated great abilities in physics and mathematics.
Yuri Kondratyuk later enrolled at the Peter the Great Petrograd Imperial Polytechnic Institute to study engineering, where he was influenced by Ivan Meshcherskiy.
Yuri Kondratyuk included detailed calculations of the trajectory to take a spacecraft from Earth orbit to lunar orbit and back to Earth orbit, a trajectory now known as "Kondratyuk's route" or "Kondratyuk's loop".
Yuri Kondratyuk left the army in 1917 following the Russian Revolution and tried to make a living stoking boilers back in Poltava.
In 1920 Yuri Kondratyuk made an attempt to escape for Poland but was stopped and turned back by border guards.
Under this new identity, Yuri Kondratyuk lived in and around Kuban and the North Caucasus, working as a mechanic and railroad worker.
Yuri Kondratyuk suggested using a gravitational slingshot trajectory to accelerate a spacecraft.
In 1925, Yuri Kondratyuk made contact with Moscow-based scientist Vladimir Vetchinkin and sent him the manuscript.
Yuri Kondratyuk's discoveries were made independently of Konstantin Tsiolkovsky who worked on spaceflight issues at that time; the two never met.
Yuri Kondratyuk learned of a competition to design a large wind power generator for Crimea, sponsored by Sergo Ordzhonikidze, then People's Commissar of Heavy Industry.
Yuri Kondratyuk immediately decided to divest himself of his own copious notes on the subject.
Yuri Kondratyuk sent a copy of his published work to the Tsiolkovsky State Museum of the History of Cosmonautics in Kaluga.
Yuri Kondratyuk joined the Red Army as a volunteer in June 1941 and died in 1942 near Kaluga.
Yuri Kondratyuk's unit was involved in heavy fighting against the Nazis in October 1941, and 3 October is sometimes given as the date of his demise.
Yuri Kondratyuk was inducted into the International Space Hall of Fame in 2014.