Would there be super-futuristic parts that are possible (In theory) to build, for example, a Light-electricity conversion based particle annihilation powered particle accelerator engine (it requires advanced technologies, including the mass production of Graphene and high temperature super-conductive material to construct), which is a type of super efficient anti-matter engine that have insanely high specific impulse (Like 1*107 second) or a Helium4 or Protium or Carbon high-pressure thermonuclear reactor.