How would I create a dampening system for a vehicle in a zero-gravity environment?

I have created a space ship using mainly VectorForces to control it. I know that to create a dampening system I would have to detect Velocity on a certain axis, and then apply another force to counter it until it reaches zero, but I don't know what the math would be. Basically, I want the space ship to slow to a stop whenever the player doesn't want to move.