>>12552339>Is this type of engine more or less interchangeable with gas-generator engines? Not very familiar with the tap-off approach.No, they're completely different.
In combustion tap-off you take hot gasses directly from the main combustion chamber and use them to spin the turbine. With magic materials this can actually be the best cycle, unfortunately magic isn't real and this cycle sucks ass as a result, because you have to deal with shit like 'melting' and 'erosion'. If we had materials that could operate at >3000 celsius we could design rockets that had guts more like airbreathing jet engines, where the front of the pipe has fuel and oxidizer inlets, the liquids get spun to super high pressure, they flow into the main combustion chamber and burn completely, then flow out over a turbine and out through the nozzle. This shit would be amazing in terms of TWR and efficiency and thrust, but it can't exist. FFSC is the real world ideal, and it's a bit more complex and heavy, but still ideal with what can actually be built.
Gas generator works by splitting off a small amount of fuel and an even smaller amount of oxidizer to burn in a small, extremely fuel-rich combustion chamber. The hot-but-manageable gasses from this small chamber blow across a turbine and spin the pump impellers. This cycle is pretty simple and not that efficient and doesn't offer massive combustion chamber pressures BUT it's easy enough that you get a worthwhile engine if you don't design it stupid on purpose. If you're really smart like SpaceX you can build a kerolox gas generator that mogs most engines of any description, due to being relightable and extremely reliable and also have yuge TWR.
