A shock tube model was developed to predict diaphragm opening time, shock acceleration, and shock formation in a rectangular channel. Heat transfer and friction effects at the tube walls on shock acceleration were analyzed. The model was compared to shock tube experiments using slit-type (fast opening time) and petal-type (slow opening time) diaphragms. Helium and air were used as fluid media in the high-pressure and low-pressure sections of the rectangular shock tube, respectively. Due to the high-aspect-ratio of the rectangular shock tube cross-section, a methodology was developed to produce petal diaphragms resulting in consistent bursting pressure, petaling without fragment release and symmetric opening resulting in a symmetric shock wave. Schlieren imaging was also used to investigate the shock wave structure development.