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SESK: Stuff Everyone Should Know · sesk.info/aero-x15-mach67

The rocket-powered X-15 set a speed record of about what?

About Mach 6.7, roughly 4,520 mph.

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  1. About Mach 2
  2. About Mach 25
  3. About Mach 6.7 ✔

Why: The X-15 was dropped from a B-52 and used a powerful rocket. It reached 4,520 mph and flew as high as 354,200 feet, which is in space by some definitions.

Huh, didn't know that: The X-15 flights ran for nearly a decade, from 1959 into the late 1960s.

The dad joke
Why did the X-15 need a B-52 to get started? Even rockets need a ride sometimes.
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References

Answer: About Mach 6.7. The X-15 was dropped from a B-52 and used a powerful rocket. It reached 4,520 mph and flew as high as 354,200 feet, which is in space by some definitions.

  1. X-15, NASA www.nasa.gov/reference/x-15
    4,520 mph (Mach 6.7) and 354,200 feet, respectively.
    Checked 2026-10-10.

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