Seoul: North Korea said Friday that it had successfully tested a new solid-fuel intercontinental ballistic missile, marking a major breakthrough in Kim Jong Un’s banned weapons programs. But what exactly is a solid-fuel missile and why does it matter that Pyongyang now has one? AFP takes a look at what we know: What is a solid-fuel missile? With this type of missile, the propellant — the fuel that powers it — is made of a solid chemical mixture, which is combusted to create exhaust. “This propellant is cast into the missile’s airframe when the missile is built: imagine a firecracker…