The key to high-energy stages was to use liquid hydrogen as the fuel. Liquid hydrogen fuel appealed to rocket designers because of its high specific impulse, which is a basic measure of rocket performance. Specific Impulse is the impulse delivered per unit of propellant consumed. You might think of it as the efficiency of the rocket. Compared to an RP-1 (kerosene) fueled engine of similar size, liquid hydrogen fuel could increase the specific impulse or efficiency of an engine by 40 percent. The combination of hydrogen and oxygen for propellants made the moon shot feasible.
Many historians agree, the U.S. took its first step toward the moon in the spring of 1957, four years before President Kennedy declared the national goal of landing a man on the Moon, and returning him safely to the Earth. While still preparing for the launch of its first Jupiter (May 31 1957), the Army rocket team at Huntsville, Alabama, began studies of a booster ten times more powerful than the 150,000-pound thrust Jupiter…
In total Ranger 9 transmitted 5,814 good contrast photographs during the final 19 minutes of flight. The last image taken before impact had a resolution of 0.3 meters per pixel. The spacecraft encountered the lunar surface after 64.5 hours of flight. Impact occurred at 14:08:19 UT right on target in the Alphonsus crater. Impact velocity was 2.67 km/s. The spacecraft performance was excellent.
In late March, 1958, President Eisenhower publicly announced the United States’ intention to launch a spacecraft to the Moon. He assured the nation that this was not science fiction. It was an achievable goal presented by leading scientists. The announcement came less than 2 months after the first US satellite had reached orbit. The President was committing the nation to a space race to the moon with the Soviets. If all went well the country would have a spacecraft in orbit around the moon before the summer was over.