EXPLOSIONS:

An explosion has two "active parts":
- the fire ball - which heavily damages everything in range
- the blast - hot air with some debris which evolves very fast, damages everything that is not "heavy armored"/protected.

The fire ball and the blast starts at the same time with different expanding speed. They always grow, something cannot just appear there at its biggest size and then retract. Explosions never retract they just fade.

There are some types of "fireballs" - the light white globe (like manga), the normal fire explosion (see the beginning of Star Wars: Episode III) and I think there is more but I don't remember now.

A large ship can break aparts with small normal fireballs or can blow up in a light globe. A small ship always explodes with a normal fire explosion (even that
can be blue or green).


DAMAGE:

You may have a linear damage distribution over range or an exponential one. Hot spot (maximum damage) can be in the middle or at the bounds (with interesting results).

Good luck!

Ships don't normally Implode in space (the explosion going within), since unlike underwater (lots of pressure) there's a complete absense of pressure in space, so ships would explode outward and keep on going. Fire doesn't behave the same way in space either, and tends to be more spherical in shape (because of the lack of gravity), in microgravity it can sometimes be almost undetectable (here's a few links for some info and a picture of flame in zero-g).

You could always have a ship simply break appart with or without small flames, or go for a sphere of fire that fades as it expands and disapates. Having an invisible radius of gasses that move nearby objects away would also fit with how an explosion in space would occur (the force of the decompressed gasses accelerating out of the ship would bounce off nearby objects and push them away).