Is the Spore Drive one of them?
Easily. The result of Bryan Fuller evidently not knowing the difference between a fringe theory and solid science.
Warp drive, on the other hand, depends on Alcubierre’s metric. A purely mathematical solution in relativity that requires negative energy in quantities we don’t know how to produce, or if it even exists in usable form.
Once the bubble is moving faster than light, no signals can pass in or out, which means the crew couldn’t steer or stop it. The front of the bubble forms a horizon that blocks information, making navigation impossible. There’s also the fact that, you can’t even form the bubble locally without already having exotic matter spread out ahead of you. And on top of that, no one knows how to collapse a bubble without dumping catastrophic amounts of energy.
Actually there's been decades of theoretical refinement of Alcubierre's initial idea, and theorists have found workarounds for a number of the warp metric's problems. They've found a way to do it with only
locally negative energy (less than the surroundings, but still positive), they've reduced the energy density required, etc. So it's not impossible to believe that another few hundred or thousand years of scientific advancement could solve the other problems with the metric. (In my Arachne-Troubleshooter Universe, warp drive and wormholes are only possible thanks to incredibly advanced "programmable quark matter" created by higher intelligences millions of years ahead of us and handed down to younger civilizations.)
The thing that's nonsensical is to assume that a work set centuries in the future has to limit itself to the physics we understand today, that nobody in the intervening generations has learned anything new. That's not embracing credibility, it's throwing it out the window altogether. That would be like writing a present-day story where there was no Maxwell's equations, relativity, or quantum mechanics, so that there were no electronics or transistorized devices. Science fiction allows -- and
requires -- speculating beyond what is known. That's the whole point of the genre. The key is simply to keep your conjectures
consistent with what we know, and to make them sound plausible enough that the audience is willing to suspend disbelief and accept the illusion. Because this is an illusion, not a dissertation. Nobody watching a magic show believes the woman is really sawed in half; it just has to be faked convincingly enough that they enjoy playing along.
And about Trek doing warp correctly... no, not really. The show’s warp core, dilithium crystals, and subspace patchwork are just technobabble. What Trek gets right is the broad idea that faster-than-light travel might involve bending spacetime instead of moving through it. The execution is fantasy, however.
No, it's conjecture. It is an error of vocabulary to treat those as synonymous.
A warp core is a matter-antimatter reactor. It's obvious that matter-antimatter annihilation, the ultimate energy source in the universe, would be the only plausible power source for a warp drive, so I can't imagine what you think is implausible about it. The only implausible thing Trek has done with warp cores is sticking them in the middle of the engine rooms rather than way outside the ship so the crew would be insulated from their waste heat and radiation (which is probably what Jefferies intended by putting the engine nacelles on long pylons, a credible detail right there). Well, that and overusing the concept of a warp core breach (initially introduced plausibly as something that could only happen if multiple redundant safeguards simultaneously failed) to the point that cores blew up if you looked at them funny. But those are problems with the execution, not the concept.
Dilithium is speculative, yes, but it isn't impossible that future civilization could create or discover minerals we don't know of today. The
TNG Technical Manual offers a pretty credible-sounding explanation for what dilithium is and how it works. It's imaginary, of course, but it's grounded in enough real science and mineralogy to be a plausible speculation.
The way Trek treats subspace is often fanciful, yes, but the concept of a "subspace" comes from real physics and mathematics; it's a lower-dimensional subset of a larger-dimensional space. M-theory suggests that our universe has 11 dimensions in all, most of them "curled up" too small to observe. It would be valid terminology to refer to either our 4 dimensions or the other 7 as a subspace of the total 11D space. In my first work of published Trek fiction,
S.C.E.: Aftermath, that's exactly how I explained what subspace was.
So if you strip things to the core: controlled atavism, technically grounded but ridiculously hard; warp = kind of plausible and mathematically pretty but probably impossible.
Again: "Plausible" is all you need in science
fiction. It's not pretending anything is real, it's just exploring an entertaining conjecture. The conjecture beyond what we know is the entire point. It's just a question of whether that conjecture is extrapolated from known science and logically reasoned, or just pulled out of thin air and slapped together randomly.
There's even a subgenre of science fiction where an author starts with one thing that's clearly impossible, then explores the logical consequences if it
did exist with as much credibility and scientific accuracy as possible. For instance, David Brin's
The Practice Effect takes place in a universe where entropy works backward and things get better the more they're used rather than wearing out. It's a nonsense idea, obviously, but he explores all the consequences in a logically worked-out way. It's a thought experiment: If this one impossibility were true but everything else about science still worked the same, how would it affect everything else? All science fiction is ultimately thought experiments. It's the genre of "What if?"