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Home » Space/Science

Question for TB. March 5, 2014 8:39 pm bowser

I was looking at a film of a launch of an Apollo / Saturn V rocket.  It took off straight up, then leaned a controlled amount, and so on.  Successful launch.

It was beautiful, and left me with some questions which I’m sure have obvious answers.  But the answers are part of the beauty.

That rocket started out at about 333 feet tall, maybe 45 or 50 feet across.  And it flies straight up, leans a controlled amount, keeps itself from spinning and goes where it’s supposed to.  With only the rocket engines at the very base of the rocket for propulsion, balance and steering.

I’m going to assume that each of those rockets operates slightly differently that every other rocket, that there is a nominal rating but that they do vary.  Sometimes one of them just stops.  And about then the flight plan calls for the entire assembly to lean, a precise, controlled amount.

Now it’s a long ways down from the top of the rocket, which would be the first place for an error to be noticed,  down to the burning rockets.  And then it can be a complex adjustment of thrust to keep the nose pointed where it’s supposed to be going, especially with unpredictable changes happening with the rockets.

And the adjustments have to be fast, information from the top of the rocket regarding pitch, speed and yaw has to get down to the other end very rapidly, adjustments calculated and implemented immediately so as to keep the entire thing within an envelope.

It seems to me to be impossible.  Once the top starts an unplanned “lean”, by the time the data gets to the engines, the correction calculated and implemented, and then the effect felt at the top, some other anomaly would have occurred with the same process having to be overlaid upon the first.

How the hell do they do that?  I know they do, I know it’s “computers” and “sensors”, but how so fast, so subtle and so accurate from initial detection to implementation to effect?  It beats the hell out of me and is part of the beauty of every launch of a large rocket.

Thanks for whatever attention you can give this.

  • Most modern liquid rocket engines are "gimbaled." by TB 2014-03-05 22:56:06
    • They are indeed. by bowser 2014-03-07 21:21:30

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