One thing has always bothered me about sf/warp drive.
Space is full of crap. From dust to micro and macro meteroids, to asteroids up to the occasional rogue planet.
How do you avoid bumping into all this stuff going that fast?
You use a powerful magnetic field to divert particles aside as you go. Its not that big of a deal until you start reaching significant percentages of the speed of light (c) at which time even atoms of hydrogen hit so hard they instantly convert into very energetic Gamma and X rays. Not to worry though, we have not built anything that is capable of accelerating to that kind of speed, and won't any time soon.
My point is that you cannot begin to build that kind of power source, or the engine to use it, or the structure required to contain it and withstand its sustained thrust, until you can build the different manufacturing capabilities in high earth orbit, such as a LaGrange-2 Halo orbit a million miles out from earth in a gravity and atmosphere free environment. The industrial processes possible there are would be considered too hazardous to attempt on earth, and everything you need for an interstellar craft cannot be made and lifted out of a gravity well. Too expensive and you cannot move the really big stuff you need, like structural construction components.
Smelt iron and nickel with sunlight and make as much stainless steel as you need. Someone needs to invent a mill that can produce hot-rolled coils in a weightless environment. Purify gigatons of carbonaceous asteroids to produce carbon fiber, and produce enough resin to start making useful structural shapes and custom 3-D printed carbon components for whatever you need. Those same asteroids will yield enough water ice to produce pure water along with pure hydrogen and oxygen fuel using unlimited sunlight. There's enough raw silicon in the asteroid belt to make unlimited numbers of highly reflective mirrors to use that unlimited sunlight. None of this is "unobtanium" either. It is all there for the taking once some smot guy figures out how to do it and make a solid buck.
I'd love to see a path to interstellar space but figuring out how to use the nearly unlimited raw materials and energy available to us in HEO is the key to getting there.
