I think I inferred some stuff that isn’t supposed to be in regards to the d20 system and I am looking for some clarification…
When players are completing a Task, do they only ever roll 2 d20? No matter the difficulty? Unless additional dice are purchased with Momentum, Threat, Determination, or Talents?
So far, the way I’ve played it, is if a Task is Difficulty 4 then I’ve allowed the players to roll four d20 to make their attempt. If they wanted to roll more than that to guarantee success, I allowed them to purchase additional dice using the above methods. Is this correct?
If I’ve been doing it wrong, how are the players expected to complete a higher level Task if they do not have the Momentum to do so?
Well, the rules are yours to play with, in all ambiguity of the aforementioned statement. So, if your group is fine with a more cinematic approach with easier tasks, everything is completely fine!
But, actually, yes, you seem to have done it in a way that was not exactly intended by the developers.
The “2d20”-system bases on rolling 2d20. Hence the name. So players, by default, roll 2d20 for any given task. The difficulty only regulates how many successes are needed, not directly how many dice are rolled (there is an indirect link since it’s impossible to score more than 4 successes with 2d20 so with difficulties greater than 4 you will always need additional dice by Momentum, Threat, Determination, Talents, or – assistance by ship and/or other players).
You may want to (re-)read pages 78 ff. of the Core rulebook on “Attempting a Task” and “Improving the Odds”.
Ok, what no one mentioned here, though you can get it from the book, is that if they do not have enough Momentum to purchase dice to accomplish said task, they may buy more dice by giving Threat to the GM.