I see, but what matters is what the players know. For example, I kinda thought along the path of the stargate: universe plotline, where I figured the aliens wanted the ship for something, like its technology.
I'm not saying that's a bad plotline that you put in there, but at the time it just seemed...convenient. I don't know, you probably have a much better handle on the plot than I know, it just kinda looked that way.
I'm not really sure, but some things seem a bit too....convenient? Like say, the aliens happening to attack just as the Ark jumps away from the planet. Things like that sorta seem like awkward plot holes, and I have found that plot holes kinda tend to make people stray away from roleplays. It makes it seem like the story wasn't all that well thought through.
Smaller and more focused may be better as well. Larger roleplays do take much more control, and odds are one or more people will at some point drop out. Perhaps a smaller more dedicated group would stick with it better.
Hmm, well it seems like we have three options then. We can continue, and hope that the other two people actual do join. Or we could kill the roleplay, which would be a shame, and not something I would support.
Or we could try to redo it. Take a break and rework some things with the story, polish things up, then start over again and see if that works.
Whatever you choose, I would hate to see the roleplay get shut down, its a fun concept and world that you have created.