The following formulas are used if AllowAlternativeCombat is on. In this case, results can be fractional numbers, and damages are tracked in fractions. Therefore, weapon hits can do less than one point of damage.

Shield_damage =
   (Expl_Power * Eff_ShieldDamageScaling
    + Kill_Power * Eff_ShieldKillScaling) / (Mass + 1)

Hull_damage =
   (Expl_Power * Eff_HullDamageScaling) / (Mass + 1)

Crew_killed =
   (Kill_Power * Eff_CrewKillScaling) / (Mass + 1)

Eff_XXX means the effective value of a configuration option, which consists of the actual configuration value plus any experience modifier of the unit being hit (these are the defensive bonuses).

This is a testing version.
It may be incomplete, and have more bugs (or features) than the public live version at planetscentral.com.