I really liked Stephen Hawking. His logic somewhat paralleled my own.
The system -- the Universe (U) -- is infinitely closed (wide shut). Therefore, the system -- the Universe (U) -- is infinitely open (wide open). Binary (1 and/or 0) "naked singularity" (the Big Vortex).
The Large Hadron Collider is a closed environment, its drive, its particle accelerator, an 'external force'. No particle externally driven can ever reach the speed of light. It's naturally leashed, it has a natural brake on it. No engine internally can ever develop so-called "light speed" within its confines.
But an engine under constant power (constant self-propulsion) could possibly power a space ship at constant acceleration without any limiting factor, excepting possibly the environment it may be traveling through at the time. Its drive, as 'position', would never know the ship's 'velocity' through the medium of space (the principle of uncertainty would apply).
Interplanetary space is enormously flatter in plane (straighter in lines) than Earthly space -- for any self-propelled conveyance under constant powering (constant acceleration). Interstellar space enormously flatter in plane (straighter in lines) than interplanetary space -- for any self-propelled conveyance under constant powering (constant acceleration). And intergalactic space enormously flatter in plane (straighter in lines) than interstellar space -- for any self-propelled conveyance under constant powering (constant acceleration). And getting from one plane to the other most swiftly must take the form always illustrated of a jet shooting out from a blackhole. In other words, any self-propelled conveyance under constant powering (constant acceleration) taking lines perpendicular to those planes, or pretty much perpendicular (thus essentially creating its own wormhole effect plane to plane, to plane).
Even getting from place to place within interplanetary space, once constant powering is developed, may require first leaving interplanetary space -- to near interstellar space -- and returning to it elsewhere, popping out and popping back in, curving out and curving back in. The same for interstellar space. And the same for intergalactic space. And so on if there is any "and so on."
I don't see that those UFO's being talked about so much in the news these days traveling through our space, popping in and popping out, going in one direction and then seemingly instantly changing to another, seemingly able to traverse any environment swiftly, then disappearing altogether, are doing such impossible things as are being described, and tracked, as being virtually impossible. Such actions happen, at least, all the time in the realm of the small (QM). If space and time are not quite what we think they are, then those vessels, those travelers, if they are real (if they are really here rather than elsewhere and only mirage real here), aren't doing anything quite as impossible as they are being observed to be doing. It would seem that we are just way behind the times, at the Jules Verne stage of understanding, with quite a way to go to catch up, in our knowledge of real space and time, as well as our quality of "space" transportation. Those UFO's easily fit into an inertialess Universe. They fit at least one description of inertialess. I'm reasonably certain my dimensional description fits just as well.