E.g. Soldier under fire.
First, the game checks if the soldier is hit. Second, it makes armor save roll (separate roll for armor and shield - if applicable). How does the game calculate armor saves against missiles? Any formula?

Does the armor/shield work only vs missiles or in melee too? If it works in melee - is it the same save roll/formula as for missiles?
We know the melee kill probability formula (based on attack/defense) but how the armor fits into this formula (or any other formula)?