The Inertia Dampeners are automatic controls built into all propulsion systems that allow ships or jetpacks to be flown in a manner more intuitive to Engineers used to the pull of drag and gravity. They can be toggled on or off by pressing the 'Z' key by default.
When switched on, jetpacks and ships will automatically attempt to reduce velocity to 0 in all directions that do not currently have a manual control activated; e.g. if the player is not holding down 'W' to move forward, then the reverse thrusters will automatically deploy to reduce forward velocity to 0.
Wise use of the dampeners is essential to becoming a good pilot. Dampeners should be toggled off on long journeys to save on the fuel of constant forward movement, and should be switched on when attempting to maneuver tight spaces. Engineers that prefer a more realistic option may choose to leave them off permanently.
The personal jetpack's inertia dampers are more powerful it's than manually controlled, which is unqiue to only the personal jetpack - ship thrusters are no more or less powerful with or without automatic inertia dampeners.