i think that we need to find a way to incorporate mass of the engine into the efficiency equation, cause you could make a perfectly efficient engine of 5000 thrust, and have it weigh 0.000000001 mass units, making it way overpowered, or have an engine with an efficiency of 30 and max thrust of 30, but make it weigh 40 mass units, rendering it useless, even though the equation says it overpowered. this way we can have more or less efficient engines without having them be accused of being cheat parts for challenges and campaign mode. OR we could balance weight of the engine dependent on size, crash resistance, and heat tolerance, and make heat production dependent on efficiency and weight. this way you get a triangle of values, but they don\'t all have to be in the same equation.