I remember something like that, but I can't be more precise. At least I'm sure there is a success level for the nebulae. For the Neineul vault scenario, you're rewarded for opening the vaults faster; for the golem fight, I think the faster the better; for the starbases scenarii I don't know if it's speed or number of loses (maybe both).
Sorry I can't be more helpful. The wiki, maybe...