Both physical and chemical aspects are an integral part of developing any sort of icbm capability, for instance; when a rocket lifts off you need a special kind of fuel, when it reaches outer space you need a different composition of fuel from the lift off stage, and in-between those two points there are many stages of chemical reactions within the rocket engine to proper the system in the air (chemical engineering is a must here).
As you mentioned we need a solid understanding of physics, from aerodynamics, to good old Newtonian physics, to orbital mechanics. it is not something your average joe can understand or even implement on a practical level. but it is doable and all we need is a government with sufficient funding and friends in the international arena to advance such technologies, e.g. Russia helping North Korea in advancing it is ballistic missile capabilities in miraculous short period of time.
Tavelling on different speeds and how gravity manifests itself in those circumstances, with G's, Angular momentum, directional speeds...etc. i am not well-versed in this area, but what i know is that we need experts both in theoretical and applied (practical) physics to implement a decent icbm program.