Old 05-30-2020, 04:15 PM
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rickair7777
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Originally Posted by Bahamasflyer View Post
Just watched the launch of SpaceX and it got me wondering? What altitude does one have to reach in order for mach # to become meaningless? Is it a sudden thing, or gradual?
Gradual, and it becomes meaningless when the atmosphere becomes so thin as to have negligible affect on vehicle performance.

On re-entry, the shuttle started measuring mach at M 25. Nope, didn't forget the decimal.
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