The lines between singleplayer and multiplayer are quite blurred, because they are effectively the same thing.
On any crew, which isn't filled with players, AI crew members can be "recruited" to fill empty roles. The Captain can issue orders to the AI crew and they will do their best to fulfil them. The Captain can jump into any of these AI controlled roles to take over, and when he/she leaves the role the AI will take over again.
In "singleplayer" the player is the Captain, and all roles are (by default) filled with AI crew members. He/she can issue orders to them, or jump into positions as necessary.
At any time while playing singleplayer the player can open up the server to other players. He/she can remove AI crew members to make room for these players, or they can create their own crew/ship (if the host player has allowed multiple player ships).
The Captain must always be a player, we won't have an AI which issues orders.
In singleplayer you play the same missions/campaign as you would in multiplayer. Missions and the campaign will have narrative.
The AI crew members are a large undertaking, I already have an experienced developer lined up to work almost solely on it. That development won't start until after an alpha release.
Thanks! I hope that answers your questions.
