>>12311163With all fuels you have a trade-off between density and specific impulse.
Hydrogen has the best specific impulse, however you need huge tanks and tubopumps, wich causes the tanks and engines to get heavier.
On the other end you have kerosene, often chilled for even higher density.
It doesn't have a good specific impulse, but your tanks are much smaller and engines if the same size can produce a lot more thrust.
To take some relatively simmilar sized rockets as an example:
Falcon heavy is purely kerosene fueled while Delta IV heavy is purely hydrogen fueled.
The advantage in fuel density allows FH to take more mass of fuel and run higher thrust per booster than Delta, wich makes up for the worse specific impulse of the engines.
The result is more than 2x the payload capacity into low earth orbit.
Only at realy high energy trajectories far beyond earth orbit the FH starts to suffer from its undersized upper stage and Delta catches up.
The sweetspot however seems to be inbetween hydrogen and kerosene, methane and propane offer a better trade-off.
These are also cryogenic fuels, allthough methane and especialy propane don't need anywhere near as low temperatures to stay liquid as hydrogen.
Propane can even be liquified at room temperature with a few athmospheres of pressure.
Meanwhile liquid methane has a simmilar temperature to liquid oxygen, wich allows for common bulkhead, wich saves weight.
The ultimative yeet machine for high energy trajectories would be a Falcon heavy that first burns out the side boosters, then burns out the center core, then burns out the upper stage, wich is followed by a single engine centaur.
