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.