Modern space launch vehicles are liquid fuelled because it’s the most energy-dense fuel and you can shut the rocket down if necessary. In SpaceX’s case, you ca

Modern space launch vehicles are liquid fuelled because it’s the most energy-dense fuel and you can shut the rocket down if necessary. In SpaceX’s case, you can also refuel the rocket for reuse. But you have to fuel it for a couple of hours on the launch pad. ICBMs are solid fuel because you can leave the rocket fuelled up indefinitely in its silo.