Yuri Kondratyuk

Yuri Vasilyevich Kondratyuk (Russian: Юрий Васильевич Кондратюк; Ukrainian: Юрій Васильович Кондратюк), real name Aleksandr Ignatyevich Shargei (Russian: Александр Игнатьевич Шаргей; Ukrainian: Олександр Гнатович Шаргей; 21 June 1897 – February 1942), was a Soviet engineer and mathematician. He 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 (LOR), a key concept for landing and return spaceflight from Earth to the Moon. The LOR was later used for the plotting of the first actual human spaceflight to the Moon. Many other aspects of spaceflight and space exploration are covered in his works.

Kondratyuk made his scientific discoveries in circumstances of war (including both World Wars and the Russian Civil War), continuous persecutions from authorities and serious illnesses. In fact, "Yuri Kondratyuk", the name under which he became known both in Russia and abroad, was a stolen identity he assumed in 1921 for his own protection.