The Tsiolkovsky rocket equation. (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) https://

The Tsiolkovsky rocket equation. (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) https://what-if.xkcd.com/7/ https://what-if.xkcd.com/7/ But this is just a minimum. In practice, everything depends on our means of transportation. If we’re using rockets, it’s going to take a lot more. This is because of a fundamental problem with rockets: they have to lift their own fuel. If we want to launch a 65-kilogram spaceship, we need to burn around 90 kilograms of fuel. (Gasoline has an energy per pound comparable to that of rocket fuel, so we’ll stick with that example). We load that fuel on board—and now our spaceship weighs 155 kilograms. A 155-kilogram spaceship requires 215 kilograms of fuel, so we load another 125 kilograms on board ... Fortunately, we’re saved from an infinite loop—where we add 1.3 kilograms for every 1 kilogram we add—by the fact that we don’t have to carry that fuel all the way up. We burn it as we go, so we get lighter and lighter, which means we need less and less fuel. But we do have to lift the fuel partway. A rocket is essentially a series of very large tanks stacked on top of each other. The economics work out in such a way that you make the tanks as lightweight as possible, and then pressurize the combustion chamber with turbopumps.