Initial shot damage is an important concept to consider in combat, due to the fact that a high initial shot damage can simulate the effects of a high DPS in the first few seconds of an engagement.
This works because for most engagements, each weapon already has a round loaded "in the chamber" from the start, because even the longest reload times are usually shorter than the times between what we call "separate engagements" (usually just the time it takes to close to within weapon range for one side),and because weapons with longer reload times usually cause more damage per shot. Theoretically, an equivalent advantage could be achieved and prolonged by repeatedly leaving an enemy's weapon range, or hiding behind cover, between your own shots
Units such as the Flapjack, the Serenity, and the Shimmer all have high initial shot damage, effectively allowing them to have extremely high DPS over short combat durations.
For example, in the case of 2 Mantis against a Flapjack, an initial look at the DPS of 63.4 (for 2 Mantis) and 520 combined HP against the 47 DPS and 264 HP of the Flapjack, it looks as if the 2 Mantis would easily prevail in a combat scenario. However, should the two parties actually engage in combat, the most likely result is a victory for the Flapjack, due to higher range and high initial shot damage.
The first Flapjack missile would launch and hit the first Mantis, for a kill, before the first mantis could begin firing, and the reloading of the missile would begin before the second Mantis was within range. The second missile would then fire and destroy the second Mantis at about the 11 second mark, a few second before the Mantis destroys the Flapjack. The initial shot damage of the Flapjack created an overall DPS of 85.5, during the 11 second engagement, despite the fact that the technical DPS of the Flapjack is only 47.
The effect of initial shot damage decreases as the duration of a particular engagement increases. However, in the early game situation, it can have striking effects.
Also note that, in addition to effectively lengthening a weapon's reload time, and decreasing its DPS, a lengthy charge-up time (see Lua Weapon) can sabotage what would otherwise be an initial shot damage advantage.