Abstract: Various enhanced rocket engine systems are discussed herein. In one implementation, a rocket engine system includes a combustion chamber, and at least one propellant tank that holds propellant in at least a liquid state. The rocket engine system also includes a pump configured to pump liquid propellant from the at least one propellant tank through a thermoelectric generator (TEG) system and a heat exchanger. The TEG system is configured to produce electrical power for the pump based at least on a temperature differential between the liquid propellant from the at least one propellant tank and heat produced in the combustion chamber during an active state of the rocket engine. The heat exchanger is configured to receive heat from the combustion chamber and pressurize the at least one propellant tank by heating at least partially liquid propellant received from the TEG system.