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Flight faster than about what speed is called hypersonic?

Faster than Mach 5, five times the speed of sound.

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  1. Mach 1
  2. Mach 2
  3. Mach 5 ✔

Why: Above Mach 5, the air gets so hot that its chemistry changes. Spacecraft coming back from orbit fly at very high hypersonic speeds and need heat shields.

Huh, didn't know that: NASA says the Space Shuttle reentered at around Mach 25.

The dad joke
Why are hypersonic planes bad at hide and seek? They're gone before you finish counting.
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References

Answer: Mach 5. Above Mach 5, the air gets so hot that its chemistry changes. Spacecraft coming back from orbit fly at very high hypersonic speeds and need heat shields.

  1. Mach Number, NASA Glenn Beginner's Guide to Aeronautics www.grc.nasa.gov/www/k-12/airplane/mach.html
    For speeds greater than five times the speed of sound, M > 5 , the flow is said to be hypersonic .
    Checked 2026-10-10.

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