So Paul, we kind of know what fuel we can and cannot have, but how do we actually get it into the rocket and make it burn? I mean, it's pretty easy, right? That's what they call it, rocket science, that nothing ever goes wrong, pretty simple. Okay, so here are some movies of things going wrong. And yes, rocket science has become a byword for anything that's really hard. It's either brain surgery or rocket science. Brain surgery on a rocket may even be the most difficult. Yes, and the reason why it's become a byword for being hard is because of all the sort of footage, probably back in the 50s and 60s. I actually don't think that designing a rocket is particularly hard than designing any other piece of high-tech equipment. Like a new camera or phone or it's just that when your new model phone goes wrong, it doesn't explode or crash into the ground and kill large numbers of... That's right, they go through iterations all development does, but yes, it doesn't end up in spectacular explosions on YouTube. Yes, so let's talk a bit about how you actually design particular liquid fuel rocket being the main type that we use. As you can see, it is quite difficult. And things go wrong quite a lot in spectacular fashion. Yes, so I mean, here's the next footage here. I'll show the take-off of a rocket. This is a case where the engine goes wrong. Okay, so it looks like it's all going well here and lifts away very nicely. And then you'll see the moment it goes... Yep. And it still got all that fuel in there, but it's not giving any thrust anymore. Which means, but it still is burning, so it has to burn somewhere and that's usually the giant fireball on the ground. Yes. So, basically the technology of rockets is not varied, in some sense, very much over like 80 years. I mean, I guess, yeah, right, that's the V2. Yes. And they kind of look the same out. They look the same up, even some of the support structures. So, I mean, they're basically using the same sorts of fuels. Yep. And the technology, as you're going to see, is more as the same. Yep. So, for all these rockets, they're basically made of something like this. They've got two tanks, a fuel tank and an oxidizer tank that fuels we've just talked about. This is not to scale, because really that will be 90% of the rest. Exactly. For those two tanks. Then you've got the turbo pumps that take the fuel and pump it into a combustion chamber. Yep. And you've got the nozzle. Okay. And so, we'll go through these in order. Yep. Because these are the parts of what you need to make a working rocket. Great. So, starting with the tanks, I mean, of course, the fundamental problem here, as we talked about with the Soul Delta V thing, That's right. Is we really have not much mass to play with? Exactly. So, we need to minimise as much as possible the tanks, which, as you said, is actually the majority of the body of the rocket. So, they've got to be contained huge amounts of fuel, and this fuel may be trygently cold and corrosive. And also, way almost nothing. So, you've got this incredibly lightweight, very large tanks. And as you said, it also has to be slosh resistant, right? That's right. Now, when it's full, it's not a problem. But as it goes higher up and more and more of the fuel is burned, it's very easy, especially when you just release one stage and about to fire another, you might have a brief moment to zero gravity. The fuel might slosh around. That's right. And I guess if it's sloshing, that means it's moving, it's mixing, throws off the balance and can bleed to some of those explosions that we saw. That's right. You might want some sort of baffles on the inside, just to stop it flying around. You're also going to keep it down the bottom, doing it moment of weightlessness, especially if you like, SpaceX are going to reuse your rocket, you're going to turn it around and come back. That's true. The fuel has to be where the nozzles are to get it out. That's right. So, not trivial, but this is a relatively easy question compared to some of the other parts of rocket design.