Can a rocket, starting back toward the earth from 30,000 feet, reach the speed o…

Can a rocket, starting back toward the earth from 30,000 feet, reach the speed of sound before reaching the earth? — WJT, Crystal, MN

Some rockets probably reach the speed of sound in a few hundred feet heading upward, so that reaching the speed of sound in 30,000 feet heading downward would be a simple task. In fact, if you dropped a highly aerodynamic object such as a rocket from 30,000 feet, it could reach the speed of sound even without any propulsion! Gravity alone will accelerate it to about 130% of the speed of sound.

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