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This is the rear end of the Saturn V Rocket's primary ascent stage. There are five Rocketdyne F-1 RP1 kerosene-fueled rocket engines here. Each F-1 can produce 1,522,000 of thrust. The F-1 was the most powerful rocket engine ever used in service.
The Saturn V Stage I. The enormity of this rocket is difficult to depict in this photo. The most complex machine man has ever produced, it was 363 feet high, and took men to the moon.
This is the rear end of the Saturn V Rocket's secondary booster stage. There are 5 J-2 hydrogen-fueled rocket engines here. There is a single J-2 on the third stage of the rocket, which was used to push the command module and Apollo capsule out of earth orbit. Each J-2 can produce 250,000lbs of thrust. Interestingly, an advanced version of the J-2 will replace the Space Shuttle Main Engines (SSMEs) that were going to be re-purposed for the Constellation/Ares program. Why the J-2? It's less than half the price of an SSME, which was designed to be re-usable. The J-2X variant will produce 294,000lbs of thrust, and the Ares booster will only be carrying one for it's Earth Departure Stage on the Ares I manned rocket -- just like the third stage of the Saturn V. For primary ascent the Ares I will use an updated version of the Space Shuttle Solid rocket booster (SRB). The main boost stage on the heavy-lift Ares V variant for moving large cargo items into space will use five RS-68 engines, which are used on the Delta-IV unmanned rockets, and will also use the J-2X on it's Earth Departure Stage.