Another example. The V2 rocket engineers had a problem with the nozzle. It would burn through. The flame was just way too hot for any known metal. The solution

Another example. The V2 rocket engineers had a problem with the nozzle. It would burn through. The flame was just way too hot for any known metal. The solution was simple and pure genius. The nozzle was composed of tubes welded together. The liquid oxygen was run through the tubes, which pre-heated the oxidizer and cooled the nozzle. But that still wasn't enough. Then the engineers simply drilled tiny holes in the tubes, so some of the oxygen would leak out into the nozzle. The gas would form a barrier between the flame and the nozzle, and would carry away the heat. (This is known as boundary layer cooling.) If you ever get a chance to look at a rocket nozzle, you'll see the tubes and the holes.