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Throttling technology is a key technology for future space transportation system. One of the most important components of the rocket engine for thrust control is the propellant injection system. The pintle injector is one of the most promising candidates due to its simple structure and combustion stability. However, the number of studies on the pintle injector is limited and detailed phenomena of the pintle injector has not been clarified. Therefore, a combustion test using an ethanol/ liquid oxygen rocket engine is carried out with a planar pintle injector in a rectangular combustor. Fundamental combustion characteristics such as characteristic exhaust velocity efficiency are acquired at the combustion pressure of 0.45 MPa and O/F=1.25 to 1.80. C* efficiency increases as the equivalence ratio increases up to unity. Flame images during combustion at 0.45 MPa and O/F=1.75 were acquired. Luminous flame was not observed in throughout all of the region except for the vicinity of the faceplate. However, strong luminous flame was observed at the time of ignition. The combustion chamber used in this research can simulate one of the recirculation zones observed in actual combustor with pintletype injectors, which contributes to the combustion stability. However, the recirculation zone formed at the top of the injector is not simulated appropriately due to the existence of the lower wall of the combustor.