The cost of this resource is a number of SP equal to the total combined starting Shield Values of all the ships in your fleet divided by 2 (round up).
The Tournament Rules says:
If there is a Blind Booster, [40] of your available Fleet Points are reserved for use with game elements from your Blind
Booster, leaving 90 points to build your fleet. The game elementsin your Blind Booster may not be mixed with the 90 points from the rest of your fleet. The Blind Booster ship counts toward the 3-ship minimum.
Can you legally play Emergency Force Field in an event with a blind booster since you cannot have a firm 90 point build until after you open your blind booster? Wouldn't this resource violate the rule about mixing game elements from your 90 point build and your blind booster?