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glhope t1_j81xig6 wrote

It’s trivia of course, but I’m curious to know if that amount of thrust is merely calculated or if there is a way to measure it. Is there a “rocket dynamometer”?

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Reliable_Redundancy t1_j828dmh wrote

There could be strain gauges on the pad, but I would imagine it's hard to calibrate them in situ.

More likely, they have lots of sensors on each engine including pressure transducers. They know from single engine tests that pressures in an engine are correlated to the amount of thrust it is producing. A little bit of math later they get the total thrust of the rocket

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amitym t1_j83vdkt wrote

Tbf you don't need to calibrate them very carefully to get an imprecise (though presumably accurate) figure like "7.9 million."

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Disastrous_Elk_6375 t1_j836fxc wrote

They're testing engines separately at the factory. They've ran hours of tests and most likely have a pretty solid understanding of what thrust each engine gives at a certain "throttle" level. So they'll have precise measurements of things like flow for each engine, and they'll know what each flow setting would translate into thrust. From there it's simple math and some approximation.

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