It Took 83 Engines to Get to the Moon

The five F-1 engines of the Saturn V in Florida. My own selfie. The first time the Saturn V launched in November of 1967, ceiling tiles in the nearby studio where Walter Cronkite was reporting from live fell to the floor. The power of the five F-1 engines was astonishing, and their combined 7.5 million pounds of thrust hasn't yet been matched. But there were more engines than just those five biggest ones. All told, it took 83 engines to get an Apollo mission to the Moon and safely back to Earth. [embed]https://www.youtube.com/watch?v=F2c9LPNRonQ[/embed] Engines and Motors First, we have to make one very important distinction between rocket engines and motors, because I can hear groaning sounds over the claim of “83 engines.” Properly speaking, the Saturn V had a total of 83 engines and motors. The difference is in the kind of fuel each burns. A rocket engine burns liquid fuel. Take the F-1 as an example; it burned a mix of rocket grade kerosene called RP-1 and liquid oxygen abbreviated LOX. The upper stages of the Saturn V also burn liquid fuels, liquid hydrogen or LH2 and LOX. Liquid fuels are tricky. In the case of the LOX, oxygen needs to be super cold to be in a liquid state, so even with insulation around the tank it inevitably warmed enough to boil off if left too long. To keep the most LOX in the tank it needed to be loaded in very close to launch. But the challenges of dealing with cryogenic liquids was offset by the benefits. Liquid engines can be throttled and restarted, two characteristics you really want when doing precision burns to adjust your trajectory on the way to the Moon. Rocket motors, on the other hand, burn solid fuel. The best example of these we have is the SRB, the solid rocket boosters that helped launched Space Shuttle missions. The good thing about solid rocket motors is they take away some guesswork; they ignite and burn, simple as that. The downside is they can’t be throttled or relit.