Have I got this correct?
"Blue Critical ....... if the defender does NOT have any command tokens, the defending hull zone loses one shield instead"
Just rethinking this card (after writing it off fairly early)....
Rules Reference Page 2, Step 5 resolve damage says:
"The attacker can resolve one of its critical effects. Then the attacker determines the total damage amount......"
So: I roll 3 red and 3 blue on my VSD, say against a frigate with three shields and no command tokens. I get, amongst other things a blue critical that is not evaded. Say after defence tokens, 5 damage including the blue crit.
The blue critical ion cannon effect takes place first and immediately removes one shield from the defending hull zone.
Then all other damage from the attack is applied, after modification for braces, redirects etc.
But the ion cannon shield loss can't be braced or redirected, and the blue crit still then counts as a damage result, so total damage is one shield plus 5 damage, unless braced, in which case will be one shield plus 3 damage. Redirects may still apply but can't redirect the ion shield loss.
Having used the ion cannon hit any applied damage cards are face down.