In 1953, Korolev was given the go-ahead to develop the R-7 Semyorka rocket, which represented a major advance from the German design. Although some of its components (notably boosters) still resembled the German G-4, the new rocket incorporated staged design, a completely new control system, and a new fuel. It was successfully tested on August 21, 1957 and became the world's first fully operational ICBM the following month. It would later be used to launch the first satellite into space, and derivatives would launch all piloted Soviet spacecraft.

Answer this question, if possible (if impossible, reply "unanswerable"): When was the R-7 Semyorka rocket tested successfully?
August 21, 1957