So that's one way. But in the short term, the advance you're seeing there with that star hopper is that I. That it's still a traditional chemical propulsion rocket. So it's got fuel and oxidizer, which is liquid oxygen, because no oxygen up there. To have fire, you need the pyramid, right? So you need the oxygen and the fuel and the spark, and you have to bring your own oxygen if you're in space, because you can't use. You don't have the atmosphere anymore, so you carry liquid oxygen and some fuel. And in the falcon nine, for example, it's basically kerosene. It's rocket fuel, but it's RP one. It's basically kerosene mixed with liquid oxygen. The engine you saw in that star hopper is advanced and different because what it uses, it still uses liquid oxygen, but instead of kerosene, it uses liquid methane. And it's actually not as efficient, quite. It doesn't have quite the specific impulse, which is a measure of efficiency. It doesn't have that quite as good as hydrogen. It's better than kerosene, but not quite as good as hydrogen. But here's the thing. You can make it on Mars, and that's why. That's why Elon's building that engine, because you can go to Mars, and you don't have to bring your gas to come home.