In contrast, the ESG in Federation Commander takes the "expanding" part to heart. While it's not relevant in defensive burst (which are only useful against drones or suicide shuttles that have "impacted" the ship), offensive bursts start by affecting the units in the same hex as the firing ship, and only expand out into the ring of adjacent hexes if there are any ESG damage points remaining.
But the ESG is used up in the event; there is no lingering "bubble" on the tabletop after it is used in FC.
As Iron Domokun says, I would sooner suspect that version of the ESG, rather than the SFB one, to be chiefly considered for use in this game system.