The screens and shields really are the "hull", you saw in the episode Day Of The Dove what happen to a klingon D7 with no shield when hit with full phasers. So no, in terms of protection, where the reactor is located is irrelavant. Another good reason to put the reactors in the nacelles is to shorten the plumbing to the coils. Mytran is right, the movies E had a single reactor in the secondary hull.
I've always thought that. Thanks for putting it so succinctly. Also, to say nothing of the range that a hostile would be at (10's of thousands of kilometers). This was another reason Khan's attack was so crippling. From the starfleet designers who gave us a bridge waaaaay up on top? (Over and over and over.)
Judging by the way that TOS ships are designed, this last point rings especially true to me; if it were actually possible to provide better protection for TOS reactors by embedding them deeper within a hull, then spheroid ships would still be the norm, with the volatile M/AM reactors right in the centre. Also, there should never be any reason why a ship should encounter another ship without shields up - they automatically snap on whenever an unknown "blip" is detected (as happens in a couple of episodes, one of which is "The Immunity Syndrome")
That's the point: it doesn't make it easier. If they can hit the nacelles, they can hit the engine room. The only way to make it hard for them is NOT TO GET HIT. On the other hand, there's something to be said for survivability. The A-10 tunderbolt has its engines in big obvious pods on the side of the fuselage. You may think it would make more sense to burry the engine in the middle of the plane underneath the cockpit, but that would provide very little protection for the engine and provide a very big hazard to the rest of the plane if something goes wrong. To put that another way: it's easier to jettison a damaged nacelle than it is to jettison a warp core and fifteen antimatter pods through a narrow hatch on the bottom of the ship. Speak for yourself. If something goes wrong with my warp core in the middle of a battle, I want it as far away from me as possible.
Yeah, it's like a deflector car alarm: shields go up at the first sign of trouble. This even happens in TNG "The Arsenal of Freedom" where the computer seemed to realize it was under attack before the crew did.
A few points about the A-10, and jet aircraft in general. The engines on that pig are the same as on the C-135, and as such, can take a lot more crap than the oh-so-fragile engines of, say, an F-15. FOD walks (making sure there's no debris that might screw up the engines on the runway) are a lot simpler for the A-10 than other fighters, where the ground crews have to practically vacuum the tarmac before their planes can even consider taking off. For an A-10, so long as there aren't any good size rocks, you're good to go. Also, the preferred nickname is "Warthog". You go onto an A-10 base and refer to it as a "Thunderbolt" and you'll get some funny looks. Another reason why those engines are out there on nacelles is because they're jet engines! They have to have big air intakes or they don't work. Warp engines don't work that way.
The same seems to be true of the Constitution's warp core, since even the thoroughly wrecked Lexington did not suffer a warp core breach despite the fact that M-5 had hit it with enough firepower to kill the entire crew. First of all, warp nacelles are supposed to work the same way (hence the need for bussard collectors). Second of all, the engines don't need to be in NACELLES to have air intakes. The F-86 and the FJ Fury both have their engines buried in the fuselage with the intake dominating the entire nose of the aircraft, same again for the entire Mig series from 15 to 21. In point of fact, the A-10s engines are isolated from the fuselage as a matter of survivability: jet engines have an unfortunate tendency to EXPLODE when something goes wrong with them, and the designers didn't exactly have "small rocks" in mind when they made this choice. If your engine swallows a 20mm API shell at five hundred knots, then it's fucked; you've got a dozen fan blades flying through the casing like a giant hand grenade. When that happens, if your engine is on a pylon slightly away from the fuselage, your chance of SURVIVING a catastrophic failure and successfully landing again are that much higher. If you're flying an FJ Fury when this happens--or worse, an F-35--then your entire plane goes up in a fireball before you have a chance to say "Oh shit." The kind of damage that can cause a warp core to go "boom" give you a small amount of warning. If not enough for the engineer, at least enough for the COMPUTER to recognize a problem. The other thing to consider is that, even if the computer isn't quick enough, it's entirely possible that a matter-antimatter detonation would be limited to the NACELLE, with the rest of the explosion being repelled by the ship's own deflector shields (which might explain the conformal skin-hugging shields we sometimes see).
The Bussard collectors have nothing to do with the warp drive. Their purpose is to scoop up interstellar hydrogen for fuel, and serve as a supplement to the onboard deuterium slush tanks. You're not gonna get enough hydrogen to run a ship the size of the Enterprise, but it might make the difference between making it to a refueling base and having to call for a tanker. The warp engines, on the other hand, generate a field which warps spacetime around the vessel, enabling the ship to, in effect, exceed the speed of light. The energy required to generate this field is produced by a matter/antimatter reactor (which, in the two instances where this has been directly referred to, "Elaan of Troyius" and "That Which Survives", is pretty clearly depicted as being inside the hull, and in the case of "That Which Survives", is explicitly described as being ejectable). The two have nothing to do with each other. It just made engineering sense to put them both in the nacelles. Also, to the matter of survivability, like you said, when a warp core start to go, there's not gonna be a lot of warning. However, the circumstances leading to that warp core breach can generally be seen two parsecs away. And if you have a situation where the thing is gonna blow in two minutes unless A, B, and C are done, do you want that reactor waaaaaaay out there on a nacelle where it takes five minutes to get to under the best of circumstances? Or where you can get to it in a matter of seconds and do what needs to be done? Remember, this isn't an airplane where you just have to worry about making it back to the field and let the ground crew take it from there, you have to be able to fix it on site. That changes the equation quite a bit. Consider this: Under what I guess can be defined as "the official model", where we have one central reactor channeling power to the nacelles, and a nacelle takes a hit or suffers some catastrophic damage, in most cases, the nacelle is knocked out of commission and the ship's warp capability is severely reduced (in extreme cases, a power surge back into the ship is created and the ship blows up, but it takes a little while to happen, say, a minute or two). Put your primary matter/antimatter reactors out there, however, and something bad happens, and ship go boom before you can even say "eject." And considering that we've seen an ounce of antimatter rip away half the atmosphere of a class M planet, no, the ship would not survive a M/ARC blowing up in the nacelle.
Irrelevant, since their placement on the warp nacelles has the exact same logic as placing air intakes outboard from the fuselage. And Bussard collectors are almost never placed on something OTHER than the warp nacelles. Which may or may not explain why Starfleet doesn't protect its warp core and engines by sinking both the core and the drive coils deep inside a large bulky hull. Actually, what I said was that a warp core breach will usually give you just enough warning to dump the core before it blows. I was referring to jet engines, for whom any catastrophic failure turns the engine into a giant hand grenade. Since A, B and C invariably require the pressing of buttons on a computer console in the chief engineer's office, I wouldn't mind at all. Basic maintenance can be done with an ordinary site to site transporter (faster than turbolifts). In "most" cases? We've only seen this happen a handful of times in the history of Trek. Off the top of my head: Reliant vs. Enterprise, Enterprise vs. Bozeman, Equinox vs. Voyager, Odyssey vs. Jem'hadar, Enterprise vs. Scimitar. The latter two cases involved relatively superficial damage that in any case deprived the ship of warp power. The former two involved severe damage to the nacelle that lead directly to a warp core breach. Only Reliant stands out as a counter example, with the entire port nacelle being blown completely off. Hard the warp core been in Reliant's power nacelle, it would have sailed off into space WITH the nacelle and then exploded elsewhere. The NACELLE goes boom, sure. But the same safety mechanisms designed to automatically eject a warp core in the event of an emergency would be able to eject a nacelle with greater ease. The only difference is the Nacelle is already outboard from the ship where an explosion can be repelled by the ship's own deflector shields, so even if the nacelle jettisons too late, the ship may yet survive. Why not? Starships habitually survive matter-antimatter detonations against their own hulls without being destroyed. Even in the case of Reliant, the nacelle was blown off by a photon torpedo with SHIELDS DOWN. Same again for Equinox, whose port nacelle was destroyed by a direct hit from one of Voyager's torpedoes. So canonically speaking, any such high energy detonation in a warp nacelle is perfectly survivable, while a similar detonation in MAIN ENGINEERING will destroy the entire ship.
The argument for putting M/AM reactors in the nacelles pretty much disappears after TOS, as the TMP style ships with their "almost completely new" engine design suggest very strongly that the reaction takes place within the engineering hull. The nacelles are now just warp field generators, although the term "nacelle" remains in use. You may have had the following in mind, but it's worth mentioning that the original design sketches of TMP Enterprise have the matter intakes placed around the deflector dish. Although nothing is ever mentioned onscreen, it does suggest that the TMP thinking was along the lines of a hull-located reactor system (which does not discount the earlier TOS reactors being located in the nacelles) "Elaan Of Troyius" has some supporting tech-talk, but it is "That Which Survives" which shows a single antimatter storage facility, located somewhere on board ship. This facility is somewhere near the exterior of the hull (to allow it to be ejectable) and is pumping antimatter continuously into the engines, thus causing the tense situation of the episode. My point is that although the antimatter is located in the ship (probably near those hatches at the bottom of the secondary hull) there's no reason for the rest of the reactors to be there as well. Antimatter can be piped up the pylons and into the nacelles, where the (very dangerous) reaction takes place. If the antimatter has to be ejected, then the resulting explosion happens on the opposite side of the ship to the nacelles, thus minimising risk. Just my tuppence's worth
Presenting an ejectable warp core, TOS style... The service crawlway that Scotty was in is just below the reaction chamber, and part of the assembly that would've gone shooting out the bottom of the hull if that little button labeled "eject" got pressed.
BTW, a nacelle is just a French word for a pod on the end of a strut or pylon. It has nothing to do with the function of the thing. They could be giant containers of guacamole and still be called "nacelles."
Regarding the term "nacelle", I read on another one of these posts that it referred to a unit that CRA just described, but one that specifically generated power. Or is that just in aircraft terminology?
Aircraft tend to have all sorts of underwing pods, of which only the possible underwing engines are traditionally referred to as nacelles. There's no semantic rule about it, though: a radar pod or a fuel tank could just as well be considered a nacelle... I'd argue the exact opposite: antimatter should be used close to where it is stored, rather than being piped through all sorts of sensitive areas where the slightest rupture in the lines could spell disaster. This regardless of whether we're talking combat conditions or routine operations. A suitable rationale for having the warp coils in standoff pods would be that warp field radiation is harmful, and should be kept away from the crew. Not too harmful, though: only the fussy Feds would care about the health effects enough to go for a nacelled layout. Them, and perhaps species that like to generate very strong warp fields for their own not so benevolent purposes. Timo Saloniemi
The antimatter, no matter where it's stored, would be routed via conduits with magnetic coils, and, like the gravity generators in the deck plates, it takes a long while for them to lose their magnetic field. The storage pods, on the other hand, probably need to kept a closer eye on, so it's best to both keep 'em inside the hull where you can keep an eye on 'em, and in a location where, if you have to, you can dump 'em. And since you really don't want completely eliminate your ship's warp capability over a wonky storage pod, it makes a bit more sense to not put the entire works in the nacelles. After all, it's a lot easier for a repair ship to bring out a new pod assembly and replacement hatch than a whole new warp nacelle. For that matter, it might even be possible to cobble together something to hold together long enough to get to base if all you're working around is a storage pod (in my setup, maybe just feed the antimatter straight from the antimatter generator directly into the injector assembly, with some conduits bridging the gap left by the now-missing pods). Besides, suppose you have a problem with your reactor. Do you really want it taking out your fuel supply if it goes wonky?
Thanks for clearing that up The more I think about it, the more sense it makes to separate these volatile components as much as possible. Keeping matter tanks in the nacelles is not dangerous – hydrogen requires oxygen to burn in and alone could not engage the M/AM reactors (in fact it would probably choke them). So with the reactors in the nacelles, I know I’d feel better with the reactive element (the antimatter) stored far far away from them!
The problem is that the antimatter is reactive with all things, not just with the other fuel component. In order to keep the antimatter from doing harm, one mustn't only separate it from the matter fuel - one must also separate it from all other parts of the ship as carefully as possible. In practice, this might be better done with short fuel lines than with long ones. (An alternative would be long but safely external fuel lines - a possible rationale for the long and spindly engine struts... Good for safety in normal operations, but bad for safety in combat or under other external threats.) Timo Saloniemi
It's worth pointing out that the one thing we've never seen in combat was a direct hit to a nacelle pylon. Hits to nacelles, yes, but never the pylons. Besides, the TMP designs have that blue stripe along the pylons and the outline of the intemrix chamber; I've always assumed these were plates of unusually thick armor to keep lucky Klingon gunners at bay.
That's true of course. But assuming that the transfer conduits are pretty much failsafe (it's only ever the antimatter PODS that threaten to lose containment, I think), then situating them away from the nacelles is still a favourable choice; if you should need to eject the pods, you don't want them taking out the nacelles at the same time! In a slight aside, what (obvious) ejectable panels do the nacelles have? As far as I know, each only has a single one (outlined in red) on the bottom, near the pylon. Not the direction I'd want to shoot malfunctioning antimatter pods in!