Thinking in the context of Composure and the topic in the main forum. Seems to me you can rarely ever fail an action?
2.0 Lock will almost never fail as there will most likely be something - Enemy or friendly ship, obstacle in range 3.
Focus, calculate or evade or reinforce as long as you aren't stressed.
Which pretty much leaves you to boost or barrel roll.
<EDIT - Here's where I go wrong and should have read the rules first!>
Barrel roll, sure might fail if you can't roll one way, but (heres where I may have it wrong) aren't you required to barrel roll any way you can, even if you must roll the opposite side to complete the action you chose? Same with boost - you have 3 different forward moves, and sure its possible all 3 could be blocked but its possible to complete a boost somehow usually.
Edited by JohnBoo
I read the rules AFTER I posted!