The F-1 was the largest liquid-powered rocket engine ever used to launch Americans to space and was central to overcoming Earth's gravity and sending Apollo astronauts on their first historic missions to the moon. Producing 1.5 million pounds of thrust and used in clusters of five to power the first stage of the Saturn V rocket, it was ten times more powerful than conventional engines of the 1950s and 1960s. It used liquid oxygen and RP-1 propellants in a 2.27 mix, stood 18.5 feet high, measured 12.2 feet in diameter, and had a dry weight of 18,416 pounds. Its first flight was in 1967, its last flight was in 1973, and it flew 65 times.