A cluster of five F-1 engines powered the first stage of the Saturn V rocket, with the Roman numeral V signifying the five engines. F-1 engines provided the power to lift the Saturn V rocket for Apollo test flights, manned flights to the Moon, and the launch of the Skylab space station. These engines lifted the Saturn V to an altitude of about 38 miles and about 6,000 miles per hour. An F-1 engine stood 19 feet tall, measured 12.3 feet in diameter, used liquid oxygen and kerosene as propellants, and produced 1.5 million pounds-force of thrust.