how large would it have to be to carry the fuel necessary to escape the earths gravity and to land again. didn’t the Saturn 5 use all of it’s fuel?
Most of it during launch. It had to lift a lot of mass. Some fuel was left to achieve escape velocity for lunar missions. Then there was the fuel in the Service and Lunar Modules.
Saturns and Shuttles used up all the liquid fuels. A few gallons (or hundreds gallons) left at MECO but not enough to do much with. I can’t remember how much residual was in each of the tanks for shuttle but it wasn’t a lot. If Jack Hydrazine checks this out he may have some numbers at hand. I know there was enough LH2 left for it to boil off and pop the relief valve on the LH2 tank.
The Saturn V forgetting about mass, weight, was 363 feet tall
(and I’m not sure if that includes the escape hatch)versus the falcon 9 standing at 180 feet, the Saturn V much bulkier as well.
It’s not just that ,, I don’t know what fuel this SpaceX rocket uses but it’s likely much more energy dense than the Saturn ,, Von Braun used cheap available fuels , alcohol and lox (V2),, kerosene and lox (Saturn)
You actually need very little fuel to land. Terminal velocity for something like this is about 400 miles an hour. So you need just enough fuel to decelerate from that speed to stop at touchdown. Plus at that point your vehicle is mostly empty tanks, so you have way more thrust than you need.