Given the size of four runabout nacelles, and the easy ability to permanently mount them in the saucer section (it certainly doesn't lack room) we come back to Mister Laser Beams question. Unless you're not going to give the saucer a warp drive for the sole purpose of not giving it a warp drive. (Although I do think the saucer would have a somewhat larger warp drive than that) If you're talking about a inflatable life-raft then sure. However with an actual lifeboat there usually is the capacity for "self-rescue" historically lifeboats were equipped with a mast and sails, and modern lifeboats have engines.
I get where you're going, T'Girl, but I do have trouble envisioning that boat going a thousand miles or so on it's own. How much fuel could that little boat possibly contain? (Admittedly, I know nothing of its specifications.) On the other hand, why are we (not you and I, but 'we' generally, in this thread) arguing about this? We saw Starfleet come to the rescue of the saucer section populace in Generations. Granted the saucer was grounded on Veridian III, but I would think that the idea is the same.
They tie all those shuttles and runabouts together to the front of the saucer and they pull it along. It's called the Husky formation. Mush! They steer it by turning Guinans hat. Sorry.
Except the warp engines...which aren't on the center line. Nope. Here's the line: He says the design hasn't "changed much" in two hundred years. The design of the internal combustion engine also hasn't "changed much" in the past hundred years...but it's gotten a hell of a lot more efficient. No, the Sternbach blueprints always had those windows as the Arboretum. The Ed Whitefire blueprints had the empty space.
Maybe we've seen different Whitefire plans, but far from empty space he placed the casino, apparently! It's certainly as good an area as any for those weird windows (and we know that Starfleet officers like to gamble). Sternbach did go so far as to label the window group as an arboretum: (click for larger) However, the space beneath it is blank and featureless. Being installed on Tuesday, perhaps? It's also rather small. A ship the size of a small city and THIS is their Central Park?!! As for the saucer travelling at "warp", I do think we need to remember that there are different forms of FTL travel, as Cary L Brown theorized on a couple of years back. That being said, I do like the image of a gaggle of Runabouts towing the (subspace field lightened) saucer to safe harbour. If Sisko's runabout can tow an entire Cardassian warship as impulse (there's no reason to think it would co-operate by lowering its mass) then what might be accomplished by a trio of them towing a friendly vessel? Finally, all this talk of the Secondary Hull flinging the saucer off at Warpspeed totally ignores the fact that it was considered an inadvisable and risky manoever in EAF. Saucer separation was designed to be performed sublight, (presumably) far from the combat zone. A shame no-one bothered to tell Picard before he took command. Or, was his Battle Bridge chair just not that comfortable?
I haven't seen "Farpoint" in a long time (mainly because I didn't really enjoy it much first run), but I don't remember questioning why the saucer would need warp drive to reach Farpoint Station after separation. I'm pretty sure that I assumed it was close enough to make it on impulse without too much delay. That said, I've never been one to pick these things apart like some people. As for lifeboats having warp capability and phasers? Why would they? I'd think that they would only be deployed as a last resort, when all other options had been exhausted. Did they deploy the lifeboats in GEN when Deanna was about to crash the saucer? I don't remember. But damn, I'd hate to see her car insurance bill.
Given the tiny warp nacelles (nacellettes?) on the Prometheus saucer section 1, Galaxy class starships manufactured post-war may be given full FTL capability, if they even build them to separate at all anymore. A smaller core could be installed, two tiny nacelles deploying from the separation cavity or something like that.
It's probably worth noting those who made-up the fictional treknology during TNG's run tried as best as they could to keep as "realistic" as possible. There was some concern over shuttles having transporters because it was felt the transporter system was too complex and large to fit into a shuttle. And along that is the idea that a warp drive is a very large, very complex, system. There was considerable debate on whether or not shuttles should have them but it was felt they could have very limited warp capability with the most basic of warp systems that probably greatly restrained their range and time they could spend at warp. (I guess think of the difference between the engine on a large starship and the boat-engine on a life raft.) Look at any cutaway of the ship and you can see how large the warp system is from the warp core, to the hydrogen/deuterium tank and the antimatter pods/generators. To say nothing of the warp nacelles and everything that's there. It's a very, very large complex system. And any look at the cutaways of the saucer shows that it clearly doesn't have a warp drive.
Actually it does have a deflector, a series of small "windows" on the underside of the saucer forward of the Captain's Yacht.
It's still can move at great velocity through interstellar space and would need a means to sweep away interstellar debris that could pose a risk to the ship, as well as a means to emit beams of energy to do whatever a phaser cannot do.
It also give a reasoning for the (invented later) refit NX-01 with its two navigation deflectors. The original one and the one on its welded on secondary hull. The original one becoming a redundant feature, but one that seems to have stayed on other, later, Starfleet ships. I still think the paired impulse units could generate enough power to get the saucer into warp. Low warp to be sure, but to a speed they can at least confortably move away from whatever the stardrive section is engaging, and head back towards Federation space. The old description of their mission would have placed the Galaxy-class well outside of Federation space for long periods of time (thus they would have families on board for a prolonged mission away from the ability to get back home for shore leave every year or five). If this is the case, having the saucer able to at least move closer to Federation space as say Warp Two would aid in the likelihood of survival and rescue, if not just them moving all the way to a dock and getting a new stardrive build under them. Of course at warp two it would take two years to travel what most rescue ships would need a week to cross. If they got it up to warp three it would take half a year to cross the same distance. Warp four would be a little over two months, but I wouldn't think a ship that sized with a fusion powered FTL Impulse drive would be able to go a warp four in TNG warp scale.
Or would FTL travel actually be necessary at all? If the subspace driver coils can lower the mass of the saucer enough for the Impulse Engines to push the ship to 0.9c (for example) then relativistic time dilation would mean that even if it took 10 years to get home, very little time would pass on board. Regarding using the MSD for an idea of how large or complex a Warp Drive system needs to be for shuttles is not entirely useful IMO, since the Warp Core is TINY compared to the overall mass of the ship. A comparatively sized shuttle core would easily fit under the floorboards!
^They don't, it's a big part of the plot of the Destiny novels early on. Impulse can push you to near light speed, but without the full warp field being generated, time dilation still occurs. In TMP when Kirk orders 0.7c, the warp core is online, the nacelles inner grilles are glowing so the field is active.
All non-canonical. There's no reason to believe that time dilation occurs in TMP. The order in TMP is "warp .5" by the way. Anyway, when has time dilation ever occurred at impulse on screen? It's an understatement to say that I miss the days when impulse drive was simply conventional rockets.
Canon, really hating that word. Anyway, point is the implication in all of Trek is, without the core and the nacelles, no FTL. Impulse can push a ship to near light speed, but even that is very rarely ever done. Without the intervention of some technology or anomaly of the week that can travel differently to how a Federation ship operates or makes it operate differently for a brief time. The saucer section has no stated warp drive, and dialouge suggests it's vunerable and essentially helpless without the stardrive as it cannot really flee unless flung away first. Even then it could be tracked and overtaken later. It's a huge design flaw, done entirely for getting a cheap "wow" onscreen early on then nearly forgotten about. There really is no point to it, Generations showed that it can fail catastrophically so easily that it seems Starfleet didn't test it out at any point prior to or after green lighting the production. And from the sister ships being blown up so easily by damage to the stardrive where no separation was possible, well, it doesn't work.