/u/JeffHoffman on I am Jeff Hoffman, MIT Professor of Aerospace Engineering and former NASA Astronaut. Ask Me Anything!19 Feb 2015, 18:02 UTC
There was tremendous vibration right at solid booster ignition on the launch pad. Solid rockets give a rough ride, because there is a lot of turbulence with all the hot gases flowing down the central cavity. But I have to say that when we went through Mach 1 on my first flight, I was so overwhelmed by the increase in vibration that I thought for a minute that something must be wrong (i.e. "Are the wings going to fall off?!). But I realized that there had been numerous shuttle flights before, and the vehicle had always held together, so I just hung on and enjoyed the ride. Once the solid boosters fall off at 2 minutes into flight, the liquid hydrogen/oxygen engines give a really smooth ride.