Note how there was no attempt at using them for Apollo and no new rocket company uses them.
The only reason so many countries relay on them because it sharing costs with ICBMs.
NASA own internal investigation suggested the same thing, but politics is more important.
Imagine you need a bunch of people trained to do X, and machines capable of Y, in order to build your missiles, but you don't need many missiles right now, but if a war against a major power broke out you'd need to ramp up production massively and instantly. Either you keep making missiles you don't need, or you somehow train people and maintain machines without actually using them, either way you're spending just to maintain readiness for no immediate value. Or you find a close enough use where you can get some value by producing something similar enough that you can convert to military use rapidly.
That wouldn't be so much political pork as actually practical. But I know little to nothing in this area, so just speculation.
In the US this is partly historical. The Shuttle style large solids have no practical military application.
In general, I think by now the technology has diverged quite a bit as the requirements for launching potentially humans and ICBMs is quite different. I don't know how closely the technologies are still linked between the solids used on rockets like Vulcan and ICBMs.
In France this is certainty the case for example.
> major power broke out you'd need to ramp up production massively and instantly.
Lets hope we don't need to rapidly ramp up production of ICBMs since they are mostly just used to carry nukes.
If you think its politically necessary to fund that infrastructure just do so with your military budget. Tying down other space activities, specially civilian, is a bad idea.
The huge Space Shuttle SRBs were never an ICBM part themselves. The military angle enters the picture when you realize the SRB fuel is the same fuel used in ICBMs, made by the same company (originally Thiokol, then ATK, which merged with Orbital Sciences to form Orbital ATK, which was then purchased by Northrop Grumman.)
Continuing rockets like Saturn 1B and doing a Saturn 1C would have been vastly smarter then all the Atlas/Thor rockets since then.
Solids were a result of military launchers wanting to continue to relay on technology for ICBMs and those ICBM producers having political influence.
Solids are a sad unnecessary diversion. They massively increase operation complexity from manufacturing to launch.
Solids are very dangerous and complex to handle. The end to end infrastructure cost absolutely does not make them viable.
Are you seriously suggesting something about operational simplicity when you are dealing with a material that is highly explosive and can easy kill a whole launch crew if badly handled?
In addition, solids require very expensive launch infrastructure to modify the boosters to fly specific routes. Check out the highly complex infrastrucutre the Europeans deploy in Kourou.
There is a reason, non of the new commercial companies even remotely want to touch solids, they are avoid like the plague.
The solid based Pegasus rocket is vastly more expensive then the air-launched liquid fueled Virgin Orbit rocket.
Japan with their solids never were a series competitor in the international launch market and their launch rates were always very low.
And solids are also never practically reusable as the expensive part is the whole fuel manufacture and infrastructure.
Solids are just a bad idea and make no sense when fully consider. Only nation state driven launchers would use them.
> Japan doesn't have ballistic missiles.
The Japanese SRBs are built by Mitsubishi Heavy Industries. Do you know what else they manufacture? Missiles of course. Not ICBMs, but they do manufacture missiles, particularly the powerful SM-3 Block II.