[NullAshton]

The shields in star trek use gravitons, projecting a force on incoming weapons. Beam weapons are refracted and disappated. Technically, they are leaky, as the more they are damaged the more leaks through. But armor dissapates the damage that goes through quite nicely. They work as long as energy can be fed to the shields, and can be redirected from other systems, such as weapons or life support. Subspace weapons penetrate them, however subspace weapons have unpredictable effects on life.