Liquid is good if the entire purpose of the rocket is to do something other than go up only and have no care about the down.
Like SpaceX’s Merlin engine is liquid. That’s because it matters for that whole boosters landing thing. So the whole coming back down matters so liquid is really worth the complexity.
Compare to say the Space Shuttle’s SRBs. They went up, got jettisoned, and then just basically fell back down into the ocean to be recovered later. The whole down part wasn’t that important.
So you can see why things like ICBMs went solid. The whole down part isn’t a big concern, well it is but for a different reason than what you would use liquid for.
EDIT: And to be sure, there’s more to it then this. Reasons to go solid vs liquid. But for the whole ICBM discussion, solid is better for many reasons, being less complex and cheaper factors into thing requiring going boom later on.
The other huge reason for going solid is long term storage and reliability. Solid engines are basically just a giant rubber eraser (Polyurethane) with a blend of 11 herbs and spices (oxidizers, etc), and thus are a lot easier to keep sitting unattended in remote silos for decades but still be ready to launch at a moments notice.
Liquid is good if the entire purpose of the rocket is to do something other than go up only and have no care about the down.
Like SpaceX’s Merlin engine is liquid. That’s because it matters for that whole boosters landing thing. So the whole coming back down matters so liquid is really worth the complexity.
Compare to say the Space Shuttle’s SRBs. They went up, got jettisoned, and then just basically fell back down into the ocean to be recovered later. The whole down part wasn’t that important.
So you can see why things like ICBMs went solid. The whole down part isn’t a big concern, well it is but for a different reason than what you would use liquid for.
EDIT: And to be sure, there’s more to it then this. Reasons to go solid vs liquid. But for the whole ICBM discussion, solid is better for many reasons, being less complex and cheaper factors into thing requiring going boom later on.
The other huge reason for going solid is long term storage and reliability. Solid engines are basically just a giant rubber eraser (Polyurethane) with a blend of 11 herbs and spices (oxidizers, etc), and thus are a lot easier to keep sitting unattended in remote silos for decades but still be ready to launch at a moments notice.