The nozzle, so as you're saying, there's a bunch of different design options, but it's a critical part of this. How much pressure and heat can we convert into thrust? Like that's really at the end of the day, that's what a rocket engine is. So ultimately, yeah, like on Earth for the first bit of launch, again, when the rockets pointing straight up and it and the engines are pointing straight down, they'll flaming down. And so that's kind of your biggest enemy outside of the Earth's atmosphere too.