the problem of this issue is that torpedos ( ammo based ) use different characteristics than guns. - at least from what i know.
a gun has no splash damage for one - but does damage to an object when it collides with its hitbox. - a torpedo/missile has splash damage - and the damage is only applied to the target if it actually affects a special part of the hitbox. - so just exploding and touching the hitbox doesn t do anything.
of course it would be better if the supernova was the very same it is now - but used 70 ammo instead of unlimited. - but then we have the nova, which is ammo based and has a HUGE splash damage - still ... when you fire it into the rear of a liner ( shielded ) the shields of the liner won t budge, cause the splash doesn t reach the shield generator. ( a gun would have reduced the shield though )
and other than those problems - we also have a huge bomber lobby that wouldn t like bombers to have their main weapons reduced to 70 ammo of course... .
but on topic:
one must not compare powerplants of each shipclasses. - they are not balanced against each other - but only balanced within. ( thats why the battlecruiser class is somewht problematic ) - you must measure percentages of what a weapon takes and how much damage is dealt for the percentage. - then you have to check how much time is needed to replenish the energy that was needed to do that damage.
for example:
- 1 supernova = around 80% of a small bomber powerplant ( 132k dam )
- 1 mortar = around 70% of a normal cruisers powerplant ( 98k dam )
* it takes around 20 seconds to replenish the energy for the bomber
** it takes - well... a bit longer for the cruiser to fill its energy up again
of course - balancewise - such a calculation is rubbish, cause the bomber will spend the next 20 seconds passivly dodging - while the cruiser - well... will be a sitting duck the next 30 seconds