Why do starships have a limited weapons range in Star Trek?

Question

In many Star Trek, we have heard references to weapons ranges. For example, a Nebula class starship has a weapons range of roughly 300,000 kilometers.

We can reliably predict that a projectile weapon (like a photon torpedo) could possibly almost continue on forever, unless, miraculously (or unfortunately), it hits an object in space.

Certain types of energy/particle weapons might dissipate or steadily disperse at a certain point--but would all types of particle weapons do so? There hasn't been on-screen evidence that a phaser will dissipate at some point (unless physics says otherwise). Ships, however, are never seen firing at each other at a certain distance--not even launching torpedoes. What limits the range of starships' weapons in Star Trek?

Answer 1

Phasers

The TNG Technical Manual refers specifically to the 'effective tactical range' of the ship's phasers as being limited by the capacity of the ship's sensors. The implication seems to be that phasers can remain coherent at longer distances, but that the target profile of the enemy ship would be so small that it would be hard to hit anything even if it's static.

Low-energy operations provide a valuable direct method of transferring ship's energy for a variety of controlled applications, such as active sensor scanning. In high-energy weapon firings, several interrelated computer systems work to place the beam on the target, all within a few milliseconds. Long- and short-range sensor scans provide target information to the Threat assessment/tracking/targeting system (TA/T/TS), which drives the phaser arrays with the best target coverage. Multiple targets are prioritized and acted upon in order. The maximum effective tactical range of ship's phasers is 300,000 kilometers.

Photon Torpedoes

The effective range of a torpedo is much larger (due to the onboard target sensors) and is limited by the amount of time that a live torpedo can keep its matter/anti-matter supplies safely contained.

While a torpedo could coast indefinitely after firing, the maximum effective tactical range was 750,000 kilometers because of stability limits inherent to the containment field design.

Answer 2

i would say that weapons are limited by their effective range, the farther the target is outside of effective range the more likely the shot will miss.

it may not look like it but spaceships move through space at ridiculous speeds even when simply drifting in space at sublight speeds, so you have to take into account of that fact when targeting one.

imagine this : a ship(A) on the edge of a solar system fired at an enemy ship(B) at the other edge across, how long do you think that shot would take for it to reach its target ?

1. none homing type of weapons be it simple kinetic weapons or energy weapons:

   • if it fired at the current position of ship(B) by the time the shot
     reaches its destination, ship(B) would be long gone since its
     constantly moving/drifting in space the crew of ship(B) wont even
     have to try to accelerate/change course to dodge the shot.
   • if ship(A) taken the time for the shot to reach its target into account and aimed at a future predicted position, ship(B) would still have plenty of time to detect the shot and react accordingly by
     accelerating/changing course.

2. homing type weapon like torpedoes missiles or straight up homing plasma balls(energy weapon) then i can only think of 2 situations where effective range actually matters :

   • torpedoes and missiles have limited fuel, therefore if they run out of fuel they will turn into simple kinetic projectiles which return us to the first point i made.
   • ship(B) can take advantage of time it has by changing course to hide in an asteroid field for example.

other than that when it comes to homing weapons the ship usually would have to rely on its own defenses.

hope that helps