There are a lot of questions on this site asking how to justify space battles at different ranges (including one by me). However, I have not been able to find much information on what range a realistic space battle would actually happen at.
The technological level in question is roughly similar to that in the Honor Harrington / and Prince Roger series. In other words:
- FTL exists, but you aren't going to use it during a space battle.
- Energy generation is done by fusion reactors / small antimatter reactors (small meaning "only produce slightly more energy than fusion"; the reactors themeselves are pretty big, and thus only on big ships).
- There are energy weapons, but they aren't useful at long ranges.
- Missiles have a long range and don't suffer as much from accuracy issues. However, there are various kinds of active and passive countermeasures.
- Shields are a globular field around ships which capture 99% of energy that passes through them, storing it in capacitors.
- Since shield capacitors aren't infinite in size (and it's rather hard to get rid of energy in space), they have to be lowered when the capacitors reach full capacity.
- The shields also have to be lowered to fire weapons out. As a result, weapons fire is generally grouped in large salvos in order to minimize the amount of time the ship is exposed.
- Shields do not block matter very efficiently. As a result, ships are rather weak to railguns.
- Railguns are only effective at very close range, for the same reason as energy weapons.
- Most missile warheads are Casaba Howitzers or radiation-pumped lasers.
- While shrapnel warheads exist, ships generally have enough armor for them to be ineffective.
- In case I missed anything, more information is available upon request.
EDIT: Here's some more details I missed.
- Ship drives produce output in the centigees.
- Battles primarily occur within solar systems, but aren't usually in orbit of planets (at least, not planets you want to remain habitable). Generally the battle is already decided once it reaches orbit.
- Yes, you can use energy weapons, railguns (although that's wasting ammo) and engines to dispel energy from shields. While this is effective over time, ships can't dump energy more quickly than it's coming in due to [insert handwavium here].