Can the CR-90 spend any amount of energy and gain 1 die each, or may it spend one energy per round to get a 5 die attack?

The latter.

Thanks for the fast reply. . .we are mid-game!

No probs, just had an Epic game last week where it came up.

The gist as I get it is that the card instructs '1 Energy, 1 additional die', you only get one use of an effect per opportunity, and there's only one opportunity because the Corvette only has a single primary attack (though I guess Gunner would do it, can't recall if that's excluded from Huge ships).