In article ,
Danny Deger wrote:
Why does the shuttle throttle to 3 Gs on ascent?

This is partly for the benefit of the passengers -- it's thought that a
healthy adult can be expected to take about 3G without testing -- and
partly to limit structural loads. (The Saturn V first stage shut down
its center engine early for the latter reason.)

There is also an earlier bit of throttle reduction, during the SRB burn,
done to keep speed down until the shuttle is out of the thickest air.
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