Yang Liwei
During the Shenzhou 5 flight, Yang Liwei became unwell due to heavy vibrations from the rocket. Although the problem was reduced somewhat by modifications to the rocket, vibrations were reported again in Shenzhou 6 necessitating further changes. According to Jing Muchun, chief designer of the Long March 2F "We made changes to the pipelines of the rocket engine, adjusting its frequency. A new design for the pressure accumulator produced evident results. The vibration has now been reduced by more than 50%".