In the rocket class, you will find this private void. Adding the small pieces of code at the bottom which are accelerate(0.95); and move(); effectively introduce a degree of deceleration. This means the rocket won't keep drifting when you have stopped pressing "up"! private void ignite(boolean boosterOn) { int currentRotation = this.getRotation(); if (boosterOn == true) { this.setImage("rocketWithThrust.png"); this.addForce(new Vector(currentRotation, .3)); } else { this.setImage("rocket.png"); accelerate(0.95); } move(); }