I got this in my log at RA3 and when I check the powers, I see nothing new. Am I missing something here...
Thanks.

Same happened to me last night as well. What is this new mistery power?

I'm pretty sure it's just Abandon Ship II.

Oh. I was thrown off because the log said "...new Rank I ability...", so I was searching up and down for a new Rank I ability.

No.

You gain new tiers of abilities from previous rank when you get promoted. You gain new abilities at the 3, 5, 8th grade of each rank.

Also, the ability gained at RA3 was confirmed by a dev to be Fleet Support: 5% chance when you go under 50% hull to have an npc ship warp in to help you. Unfortunately, it seems that at this time, passive skills do not show in the powers window so that is why we could not see what we gained.

Have you, or anyone else, ever see this proc?

There was a thread about this a few days back on the Klingon board. The guy was soloing and an NPC ship suddenly spawned and helped him fight. He even posted a screenshot. Later that day, a dev explained it in a different thread. So yes it does work. But it is only if you are level 43+, your hull gets below 50%, and you roll a 20.

(thats a D&D referance)

It's not a Space Skill, it's an Away Team Buff. It's Ground Team Proficiency.

Tactical Captains give Tactical Proficiency.
Engineering Captains give Engineering Proficiency.
Science Captains give Science Proficiency.

What does this do? I honestly have no clue.

it is a space skill
http://sto-intel.org/wiki/Player_Leveled_Abilities