If you look carefully at the analysis in my first quote, by extension this graph, and thus this limit, does not just apply to this engine, it applies to ALL engines. No engine using ANY type of thrust can accelerate at a constant rate beyond a limit where the kinetic energy of the rocket exceeds the total energy of the thrust (delta v) that got the engine to that velocity. Any rocket, any form of thrust that is linearly constant, has a Law of Diminishing Returns on its velocity determined by its kinetic energy. Under constant acceleration, the graph of the instantaneous velocity is not linear.

I do not consider stack exchange as a legitimate reference. My point is, no rocket engine can increase the rocket velocity beyond the point where the kinetic energy exceeds the total energy input, else at some point all rockets turn into a perpetual motion machine. Accelerate, slam into a heat sink, collect the energy, use it to accelerate the rocket again beyond the intersection of the curves, slam it into a heat sink, repeat ad nauseum, more energy is retrieved than put into the system. Therefore, at some point, the energy of the thrust can not lead to an increase in velocity.

Or the equation for kinetic energy can not be consistent across all velocities, or the equation for kinetic energy has to have some built-in law of Diminishing Returns factor.

Your 'diminishing mass' adjustment only applies to thrust that requires reaction mass. Given a rocket that, for instance, has the reaction mass teleported in, as it is consumed, faces the same limitation as this rocket. Also, the 'laser sail' rockets have this velocity limit. My point is, NO rocket can have a continuous thrust and acceleration beyond the kinetic energy threshold.

Let us continue this discussion in chat.

@BMF The Alcubierere drive does not HAVE to be operated FTL. But I have never seen anything really convincing about FTL resulting in arriving before it leaves. It WILL arrive before the light of it's departure, but it will STILL be 'after it leaves'. There is that 'simultaneity' thing. Completely messed up in the Alcubiere bubble. If you take your relativistic bubble with you, time does not dilate.

@JustinThymetheSecond I had difficulty seeing it until I used Desmos to make a space-time graph shift under Lorentz transformations (highly recommend, btw; there's no substitute for playing around with the transformations visually). The gist is this: any FTL motion looks like backwards time travel in an arbitrary number of STL frames (albeit highly relativistic). After completing any FTL jump, the FTL ship can take on one of those highly relativistic frames to end up influencing its own past light cone.

Because of topology, if there exists a single frame where a CTC can form, then it exists in all frames, since loops always map back to loops under Lorentz transforms.

That doesn't mean every FTL path creates a CTC. It just means after completing FTL motion, a second FTL trip is all it takes to complete the loop. You can choose not to do that, or maybe FTL is limited to a special universal frame so you can't choose to do that even if you wanted.

Oh, and about the arriving before the light thing, that's the idea that FTL time travel is some illusion to do with light. That would be true if the FTL ship remains in the same frame of its departure, which is basically equivalent to invoking a preferred frame. If the ship assumes (or is capable of assuming) one of the STL highly relativistic frames and performs FTL, it very much does arrive in its own past.

Every time I see that bit about multiple frames of reference, and the second trip forming a loop that takes one intoi the past, it reminds me of Zenos Paradoxes, particularly 3.1, The Dichotomy. Someties elicited as the toroise and the hare. Just because one can imagine it, and model it mathematically, does not make it true. The paradox is easily resolved when one considers the Planck Length, wherein nothing can be fuirther divided.

I am sure you are aware of my anti-Einstein stance, in that I firmly believe there IS a fundamental universal frame of reference, that determines and defines c (not the speed of light, but the universal constant which has the units distance/time, but is not the speed of anything). Perhaps many other (if not all) constants as well. It has as its essence a universal field that defines/determines/bounds the universe and everything in it.

The closest candidate is the Higgs Field, which univerdally/equally implements inertia in all other frames of reference. Personally, though I have no proof yet, I believe this universal field came into existence universally everywhere in the universe in an instant, along with its boson, which then defined every other boson/field.

That is, the universe started not with a 'Big Bang', but with the instantaneous manifestation of this field.The universe did not inflate, it was 'generated' as a 'field'. The entire concept of fields and bosons are just an analogy to explain or define terms in some mathematical model. Insread of 'field', the ancients called it 'aether', and really I think it was a useful analogy, a placeholder, that was unfortunately cast aside, instead of being reimagined in the spirit of quantum physics..