Coupled And Decoupled

Star Citizen takes a ship's momentum into account for flying. Due to the lack of forces in space (no air resistance, negligible gravity) Newton's First Law tells us that a body in motion will stay in motion unless acted upon by an outside force. In space, that means you just keep going. And going. And going. In order to combat that, Star Citizen implements a 'Coupled' and 'Decoupled' mode.

While you're in Coupled mode, your ship will adjust to make flying more natural. If you decrease the throttle, you expect to slow down. So, in coupled mode, your ship uses its maneuvering thrusters to slow you down. If you pull up, when you release the joystick you would like to stop pulling up, so the ship corrects for that with the correct amount of thrust, and sets you back straight. If you use your maneuvering thrusters to move a few meters to the right to avoid some debris, when you release the button to move that direction, it adjusts, and uses the thrusters to stop your movement.

In Decoupled mode, your ship does none of that. If you start moving to the right to get around a debris, that's cool! Keep on doing that! Your ship doesn't correct to set you back straight, no forces are applied, so you keep moving in the same direction.

Being able to switch between Coupled and Decoupled can allow you do all sorts of things otherwise impossible to do. For example, you can be traveling at your maximum velocity, switch to decoupled mode, spin completely around, and return fire at someone chasing you, all without changing your velocity!