I think this post from http://www.st-v-sw.net does a pretty good job of explaining why ships sometimes engage each other at the close ranges we see in the shows.
First, as to the claim of short ranges, this is sometimes true. *In DS9, it was fairly*common for vessels to close to such ranges in combat.* Sometimes this was accidental, as occurred in "Tears of the Prophets"[DSN6] when the Allies fly through a supposedly inactive weapons platform field only to have the platforms finally become active while the fleet is on top of them. **
Other times it made some tactical sense, such as when Sisko took the heavily outnumbered Federation fleet right in to the Cardassian lines in "Sacrifice of Angels"[DSN6]. *The Federation goal was to get some ships through to DS9 within a certain time limit by opening a hole for Federation ships to fight through and warp out of while the enemy fleet was engaged with the remainder. *We can also theorize that this prevented the enemy from combining too much firepower on individual ships and prevented them from targeting warp cores with abandon. *The Dominion goal was to both prevent the Federation from passing and, later, to pretend to open the hole and then surround the Federation ships, thus taking the opportunity to crush a Federation fleet. * In both cases, a fairly tight fleet formation (e.g. ships within visual range of one another) and close combat were the tactical desires of the day.
Riker gave another possible reason for closer range combat, when he believably suggested to a Klingon captain that he close to 40,000 kilometers in order to shorten the opposing vessel's response time.* This could refer to the target vessel having opportunity to adjust shield power or structural integrity or all manner of other systems to help compensate for the incoming fire and its effects. *We can even easily take this idea a bit further. *For instance, phaser beams do not move at lightspeed relative to the firing ship, so it should take at least one second and probably more for a phaser to travel 300,000 kilometers (one light-second). * A jinking and dodging ship might be a bit harder to hit*
Shorter-range combat may favor the more maneuverable vessel, as seen to excellent effect in many Defiant Class battles. *On the other hand,*ships with superior weapons arc coverage might try to keep close to try to keep a maneuverable vessel with poorer arcs from owning the fight.* * In other words, a vessel with forward-only weapons might be able to weave and dodge and take frequent shots at 200,000 kilometers, but if you are in close against them you can try to keep to their side or tail or otherwise prevent them from facing you, and if you have good coverage on your vertical and lateral sides, you can pound them with impunity.
Closing all the way to visual range could only enhance such an effect, and could (a) make it more difficult for the enemy to direct its fire against specific systems, and (b) make the concept of shoot-to-kill somewhat less attractive, since a warp core explosion is something one would prefer to steer clear of.* Such short-range combat may also be useful in regards to receiving torpedo fire, which could negatively affect the firing ship at close enough range (as noted by Riker on a couple of occasions, e.g. "The Nth Degree"[TNG4]).
It may also be that phasers and disruptors lose energy or focus or some other helpful criteria over distance, a logical supposition whether due to energy 'leakage' or simple focus blooming or frequency spread decohesion or some other technobabble.* How much loss is unknown, but s,a;; percentage points at high range could count up quickly into more required shots across the ranges available.* Thus shorter-range combat may also have the benefit of enhancing directed-energy firepower, an advantage for a vessel interested in either conserving torpedoes or with beam weapons as its primary firepower.
Finally, we also have the note from production designer Joe Johnston, who noted that the Mutara Nebula from Star Trek II was not there merely to be pretty, but to create a plot device that would allow the ships to fight at sailing ship ranges, as Nick Meyer (the director) wanted. *That's quite a bit of expense and trouble to go to just for the purpose of maintaining the reality of the universe, but it was well worth it for the sake of believability.
In short, then, there are many possible reasons why starships might fight at closer ranges despite having weapons capable of longer range fire. *However, just as occurred in Star Trek II when causing short-range fire was tactically beneficial because the odds were made even, it is logical to presume that there is tactical benefit in the other cases as well.
Translating to Star Trek, one can readily imagine scenarios in which keeping close range might be beneficial to certain vessels, insofar as forcing the enemy to limit his firepower (e.g. phasers over full-yield torpedoes), choose his targets more carefully rather than cause a core breach right beside the ship, limiting enemy maneuverability to avoid shield collisions that might knock everyone to the floor, and so on. * But this reasoning only counts against opponents of equal range.
The moral of the story is that having long-range weapon technology doesn't always mean you use it at long range. *Sometimes it is superior to go in close and fight it out.
I am in fact talking about the show in general and not the game. hence why it is in ten forward and not in sto discussion. i thought it would be obvious. however... i find those ranges ridiculous also...and i have thought of them which is what led me to this......theres no way they could be at hundreds of thousands of kilometers, and see them on screen right next to each other.
and for the person who referenced the die is cast where they rescue odo, sisko tells kira to hold fire until they are within 500 meteres.
if phasers are sublight weapons and torpedoes can be used at warp speed, why then do torpedoes take longer to reach targets than phasers.
i maintain that although they established these things on the show with their written, that their writing was inherently flawed. Impulse speed cannot be used in close range combat if it is as fast as they claim it to be on the show. Also they cannot be fighting at 100's of thousands of kilometeres when in fact we see them so close together and zipping around one another.
certainly in all fights we see in ds9 and tng, the ships are almost on top of each other. and if thats just perspective, then why are they shown so big? and not in a more distance view.
The problem is the weapons appeared to perform at relativistic speeds. A torpedo that can be fired out of the forward tube while at warp 9 ought to single handedly destroy any ship when you consider that energy equals mass times speed. A 100kg torpedo going at warp 9 would decimate a ship. But the torpedos always seem to leave the ship at the same relative speed regardless of whether the ship is moving or not.
So I wouldn't take too much stock in their abilities. One of the reasons I like STO is the torpedos have a set speed while phasers are considered instant.
If you want to talk about realism, why are spacecraft banking in an environment without air resistance?
Granted, nearly every space opera science-fiction show/movie has this problem (Babylon 5 comes to mind as an exception, at least some of the time).
"A 100kg torpedo going at warp 9 would decimate a ship."
Only if completely converted to energy, otherwise its incredible momentum (45 billion kg-m/s^2) would probably just cause it to punch through the hull and keep going. In fact, at v > c, Einstein's energy equation breaks down, as you start getting imaginary results.
What about in TNG or VOy when firing on a planets surface from orbit. these ranges are over 100km some of them 200km..
and if it were real a photon would reach more like 1million KM in range. and phasers about 500,000KM there is little to brake down light in space.
even a Powerfull pen laser would travel further than 10KM in space now.
But let's not discuss what this would do to physics. :-)
Physics is routinely ignored in Sci-Fi.
That being said, I think warp, um, warps space time. So in effect, you are not bound by the speed limit of this universe because you technically aren't in this universe. Impulse engines, if I recall, are just glorified chemical engines and rely on ye olde thrust to move the ship.