No trig tables! No formulae, please! The essense of a successful attack plan is simplicity. If you require that the captain recalculate the information the TDC already knows, he's just reinventing the wheel, introducing at least one chance for error for every unnecessary component calculation entailed. It's nice to understand the underlying math. It's stupid to actually use it to perform an attack.
Reliable systems have to eliminate every possible step. Each step increases the chance for fatal error to be introduced. Rules of thumb, such as leading by 20º for slow torpedoes and 10º for fast, are simple approximations that take the place of perilous and complicated calculations to eliminate the opportunity for fatal errors to enter the procedure.
With Fast-90 you can change your mind instantly and shoot from another angle with near-perfect accuracy anyway! You have to love a system that lets you do that!
