Experiments were conducted to investigate the effects of the penetration height on the combustion efficiency of a hydrogen peroxide/kerosene bipropellant thruster applied in a kerosene transverse injector. The penetration height of the primary breakup represents the fuel distribution of the kerosene transverse injector. The most significant design parameters of a kerosene transverse injector from a combustion efficiency perspective were assumed to be the fuel distribution and droplet size after secondary breakup. Therefore, kerosene transverse injectors were designed using three different penetration heights and a unified mean droplet size. Autoignition was stably achieved, and the hydrogen peroxide was fully decomposed for all hot-fire cases. The optimum combustion efficiency was expected for a penetration height between 44.0 and 72.4% of the inner radius of the kerosene transverse injector. The sensitivity of the variation in the combustion efficiency diminished as the penetration height increased, owing to the surface breakup of the liquid column.