The Saturn V rocket that sent Apollo careening to the moon stood 363 feet tall, weighed over six million pounds, and was primarily powered by its stage-one Rocketdyne F-1 engines, which provided 35 meganewtons of thrust. The Space Shuttle's main engine, by contrast, offered less than two meganewtons of thrust, and its two solid rocket boosters combined brought that number up to about 30. Now here's an amazing fact: Despite the massive amount of power they were dealing with, scientists and engineers weren't entirely sure of the mechanics of the F-1 engines they'd built.
Writes Lee Hutchinson at Ars Technica: "although the principles behind the F-1 are well known, some aspects of its operation simply weren't fully understood at the time. The thrust instability problem is a perfect example. As the F-1 was being built, early examples tended to explode on the test stand. Repeated testing revealed that the problem was caused by the burning plume of propellent rotating as it combusted in the nozzle. These rotations would increase in speed until they were happening thousands of times per second, causing violent oscillations in the thrust that eventually blew the engine apart. The problem could have derailed the Saturn program and jeopardized President Kennedy's Moon landing deadline, but engineers eventually used a set of stubby barriers (baffles) sticking up from the big hole-riddled plate that sprayed fuel and liquid oxygen into the combustion chamber (the 'injector plate'). These baffles damped down the oscillation to acceptable levels, but no one knew if the exact layout was optimal."
That's just one historical tidbit from Hutchinson's look at the F-1 engine, which delves into the engineering behind NASA's most powerful rocket ever and the reasons (many political) why it was replaced with solid fuel boosters. While it covers history, the story is mostly rooted in the present, because some of NASA's engineers are actually disassembling an old F-1 to fully understand how it was built and, perhaps, use that information to construct a successor.
NASA's upcoming Space Launch System may, for the first time since the Saturn V, rely on liquid fuels rather than solids. Hutchinson's article touches on liquid fuel rockets in NASA's Advanced Booster competition, a young team of NASA engineers scanning and 3D modeling an entire F-1 rocket, and, naturally, how 3D printing may show up in future engines. Check out the full story for some state-of-the-art laser scanning and an exciting test-firing of a 40-year-old engine.