Calculate time to destination given applied force and drag

I have a rigidbody who has a constant force applied to it (in FixedUpdate). There is also a drag value to keep it down to a reasonable value. There is no Gravity force in the game either.

How would I determine the time it would take to reach a destination point? Another way to ask might be, how can I calculate the max velocity given a known force, mass (1), and drag?

This should help: http://www.grc.nasa.gov/WWW/K-12/airplane/falling.html

In this case, gravity is the constant force, direction is down, but the equations should apply directly to what you are doing.