In fact the Kelvin should have been shredded long before it got under-way, with the damage it was taking.
Nero's initial goal appeared to be capturing this mystery vessel and getting intel on where Spock might have been gone. So he'd aim at those parts that neutralized the obvious Starfleet vessel's threat potential (the weapons are in the saucer traditionally) but aim away from any part that might blow up the ship.
Nero's second goal was to destroy the ship. But this quickly changed as he saw a massive evacuation underway. Thereafter, his missiles were exclusively aimed at the shuttles, doing no further damage to the ship. And after that, Kirk had steered the ship so close to the mining rig that no further missiles were fired, and apparently could not be fired - an obvious problem with "multi-warhead" or "shrapnel" weapons that require some space to be properly deployed. So it's not that big a surprise that Kirk did get the acceleration started and thus made the impact inevitable.
It never seemed to me that the Laurentian excuse was connected with Nero.
The reason I think it must be is that it would be an incredibly favorable coincidence otherwise. Nero defeated eight starships by taking them by surprise (and appears to have destroyed a further one at Vulcan, as the Mayflower wreckage doesn't correspond to any of the ships deployed from Earth), but everybody seems to think this is a fraction of the forces Starfleet would otherwise have sent.
At one point you say he is just a miner. Here you give him too much credit in my view. How is a miner supposed to convince Starfleet that 47 Klingon ships have been destroyed without actually destroying them?
That's the one way a miner can pretend to be a soldier: by sending a fake message that he is.
We later learn Nero can jam signals at will. We also learn Vulcan reported seismic troubles long before Nero actually created them - another fake message? That's the sort of thing Nero could easily preplan in the 25 years allotted, and execute with the hardware available to him.
Is the Laurentian system a Klingon prison colony by the way?
I doubt it; the Feds probably wouldn't want to move in on Klingon territory after the slaughter of a Klingon fleet...
I rather think the system where Nero first emerged might be the same where Spock later emerged (Trek time travel often works that way), and Klingons were present at that location in the teaser (mere 75,000 km away) for some reason. If this is Klingon territory, or became Klingon territory after the teaser and before the main events, then Nero might indeed have to fight Klingon ships there. But if he got red matter from Spock, this might allow him to defeat Klingons with it one hour later as indicated. Perhaps he'd just exaggerate the figures in a fake message?
Why would Starfleet send most of its fleet there without finding out a few more details?
Because there wouldn't be time to do any confirming? Laurentius is somewhat distant from Vulcan and Earth, but might still be a "last stand" location for any nastiness coming out of Klingon space (much like we see in ST:TMP where nastiness coming out of Klingon space is only intercepted by one half-finished starship scrambled from Earth).
As you indicate, this would be a somewhat unlikely situation - and thus all the likelier to be the result of careful preplanning and timing by Nero.
No reason to think Nero could tow a rock? A mining ship that couldn’t move a relatively small asteroid, a mining ship that has no tractor beams?
We have never seen ships capable of moving asteroids particularly fast, which would be the whole point of the exercise. Bombardment with little rocks would not make sense, when even ENT-level technology can deflect comets ("Demons"/"Terra Prime"); moving of large ones has always been slow and ponderous work ("Paradise Syndrome", "Rise") that could still be undone with conventional starships.
Only massive coincidences and rabbits out of hats prevented
...And only massive coincidences and rabbits out of hats allowed. Very soon, Nero would run out of those. Unless he had new tricks up his sleeve - but since he invented nothing new between Vulcan and Earth, I really doubt this would be the case.
The damage to his drill was miner, ops, I mean minor.
Or, in other words, a total loss (the second time around).
Of course, he might have had sixteen drills available in his huge ship. But this was never indicated, and frankly, 200 kilometers of thick cabling would already take up a lot of volume, even in a ship nine kilometers long. And Nero never thought about finishing the work started on Earth - he went after Spock in rage, and no Joachim stood up and declared this an unwise course of action.
If Nero went after Spock for tactically sound reasons, that is, because Spock had the means to destroy drills two through sixteen as soon as these were deployed, this indicates Nero had no other way to defend against small craft. Which makes his continuing success all the less likely.
The initial success at Earth (or even at Vulcan) is inexplicable anyway. Why is Spock the first to try and shoot at the drill? Nero may have codes to Earth's defense network (another example of him fighting a virtual war when he can't use physical weapons), and he might shut down anti-starship cannon automation and misdirect interceptor craft for a while. All this he could do with a mining rig, information obtained through capture and torture, jammers, and some 24th century computers - and the first three are established assets and procedures for him while the fourth is a given.
But he never demonstrates a means of stopping a single spacecraft from flying in all on its own and destroying the drill... Except for waiting for this to happen and then flying after the craft in revenge!
as soon as he did reload, the Enterprise would have been dead meat
How so? Twenty missiles were no threat when the starship was prepared to fire phasers at them. The next twenty should not be any greater a threat. And while Nero was shooting with his only weapon, Sulu could be shooting back with torpedoes while phasers kept Nero's projectiles harmless.
Timo Saloniemi