How Can I Rotate an object and stop

So I'm trying to rotate a spaceship 360 degrees then stop. Just like an evasive manuever. Does anyone have any Idea how I can do this. When you move left, the ship tilts to the left 20 degrees and vice versa for the right side.

But I want to be able to rotate the ship with the spacebar key.

I tried usign AddTorque but it doesn't stop rotating. Does anyone have any Idea how to do this? I just started using Unity 3 weeks ago so I'm still learning.

Thank you for the help. Also I'm using C#.