"[Shepard] was surprised by the smoothness of the liftoff," according to the NASA account. "The ride continued smoothly for about 45 seconds; then the rocket, capsule, and astronaut began vibrating. Conditioned to these circumstances, Shepard realized that he was passing through the transonic speed zone, where turbulence built up."
May 5, 2011 4:00 AM PDT
Photo by: NASA
| Caption by: Jonathan Skillings
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