It takes one pound of fuel to put one pound of payload into orbit. Because we don't have filling stations in space, every ounce of fuel you burn is to get the next ounce of fuel higher up so that it could then burn afterwards. So, suppose I want to put two pounds of payload on a rocket? I'm going to need two pounds of fuel. You're going to need a pound of fuel for each of those pounds. I need to fuel for the fuel. I needto fuel the fuel. That's right. Stay with me. We'll talk about some other stuff as well.