I think the multiple (3) reactor model best reconciles the contradictions that different writers of TOS presented us with due to their desire to use whatever best suits the needs of the story, and also meshes better with later Trek movies/series retconing as well. In any case, it’s best to keep in mind that we’re probably not going get a perfect "ad hoc" explanation that fits all the “facts” and satisfies everybody anyway, so a little flexibility is called for. Now, as to which reactor(s) is/are “the main” one, has anyone considered the possibility of a multi-stage system? I’ve been toying around with the Idea that since the resulting product from proton/anti-proton annihilation is anything but simple energy, the M/AM reactor must be equally complex. Essentially, what you ultimately end up with is electrons, positrons, neutrinos, and gamma rays. The neutrinos are lost, taking away about 55% of the energy produced by the reaction, so maybe that’s where dilithium comes in, but anyway, it’s possible to extract energy from the electrons, positrons, and gamma rays using more conventional methods. My thinking is the gamma rays are absorbed somehow in the “first/primary stage” reactor located in the secondary hull and converted into usable energy for most of the ships normal operations. But the electrons/positrons are electromagnetically separated out before they can undergo mutual annihilation and constitute the “warp plasma” that is then sent up to the nacelles to the “second/final stage” M/AM reactors where the resulting (gamma ray) energy from the electrons/positron annihilations power the warp coils. The plasma injectors we see in ST:TNG would then be of two different kinds, half would be for matter and half for anti-matter? Perhaps the warp (gravity) field generated by the coils contains the explosive energy, which explains why we see the warp plasma “sprayed” into the mostly empty space within the nacelles? In any case what we see in TNG isn’t that different than we see in TAS with what Mendel later designated as “cycling stations”, so an evolution in technology is implied? Of course, a lot depends on ones definition of what constitutes a “reactor” or “engine”. In this scheme the entire nacelle constitutes both a M/AM reactor and an engine of sorts. This way, all TOS references to “anti-matter nacelles/pods”, “power nacelles” etc. not to mention strategies to jettison the nacelles when the matter/anti-matter “fuel” is somehow endangering the ship, all make sense. Yet “That Which Survives” indicating a central and accessible location for the M/AM integrator is also satisfied. And perhaps best of all, this setup segues nicely into post TOS Trek tech. So what does everybody think?