The F-1 Engine and the Conquest of Space

The F-1 engine remains the highest thrust rocket engine that NASA has ever flown (1.5 million pounds of thrust). The liquid-fueled engine was used during the Apollo program and sat at the bottom of the Saturn V. The engines were designed to be disposable. After reaching a certain altitude, the engines would shut down and fall back into the ocean. 

When the Saturn V was taken out of service, NASA shifted from disposable rocketry to reusable rocketry. In recent years, NASA has revisited the F-1 to help inform the next generation of launch vehicles like the Space Launch System (SLS).