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Saturn: The Apollo Programme’s Intelligent Rocket
Bill Marshall
Engineer, PhD, lecturer, freelance technical writer, blogger & tweeter interested in robots, AI, planetary explorers and all things electronic. STEM ambassador. Designed, built and programmed my first microcomputer in 1976. Still learning, still building, still coding today.


January 9, 2019 08:59

That's an interesting lecture, thanks. I'm curious how the S-1C booster operated in the open-loop control mode. I'm surprised by this particular design choice since the plant is unstable. Do you know Bill or have some reference on how open-loop control scheme managed to keep rocket steady despite the system being unstable?

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January 10, 2019 08:22

@lisonator The S-1C runs open-loop because essentially its job is to fly pretty much straight up and get the spacecraft into the rarefied atmosphere at the edge of space as fast as possible. In the interval before its fuel runs out, it performs some pre-programmed manoeuvres, such as leaning away from the launch tower to avoid hitting any umbilical connection that failed to retract, and rolling to get the trajectory right for closed-loop flight after staging. The EDS monitors the flight and will signal an abort should it detect anything going seriously wrong. The rocket is designed to be aerodynamically stable and doesn't require constant feedback from a computer - unlike a modern fly-by-wire jet fighter - to stop it falling out of the sky!

January 11, 2019 16:49

@Bill Marshall Thanks Bill. Aerodynamic stability of the rocket answers my question. I was not aware about that, but looking on the fins on S-1C it seems quite obvious.

November 1, 2018 09:12

Great to get technical details, such as the LVDC voting logic. Thanks

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November 1, 2018 09:14

For some reason, even though I was 9 years old, I remember watching the Apollo 12 launch on TV and the lightning strike you describe here. Thanks for this description of the solution. Also, I am convinced my cell phone could replace LVDC, which is just how things evolve over almost 50 years.

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