Abstract: The present invention relates to a liquid propellant chemical rocket engine reactor Thermal Management System (TMS), which system comprises a reactor comprising a thermally conductive reactor housing, a heat bed, and a catalyst bed, which system further comprises an injector configured to spray the propellant in the form of a cone towards a portion of the circumference of the inner surface of the reactor housing, and an electrical heater located on the outside or inside of the reactor housing for heating said portion of the inner surface of the reactor housing.