Rocket engines are far too complex to simply apply the cube-square law. In particular, the thrust of a rocket engine does not scale with the volume of the combu

Rocket engines are far too complex to simply apply the cube-square law. In particular, the thrust of a rocket engine does not scale with the volume of the combustion chamber, but with the nozzle exit area (since exhaust velocity is independent of engine size). Thus, following your reasoning, thrust goes with the square of engine diameter, and weight as well, so thrust-to-weight is independent of the engine size.