/// Replace This

for(var x:int = 0; x <= stage.stageWidth; x++) {;
    if (ship.hitTestPoint(x, 0, false)) {;
        ship.y += 1;
        ship.rotation += 1;
    }
    if (ship.hitTestPoint(x, stage.stageHeight, false)) {;
        ship.y -= 1;
        ship.rotation += 1;
    }
}
for(var y:int = 0; y < stage.stageHeight; y++) {;
    if (ship.hitTestPoint(0, y, false)) {;
        ship.x += 1;
        ship.rotation += 1;
    }
    if(ship.hitTestPoint(stage.stageWidth, y, false))   {
        ship.x -= 1;
        ship.rotation += 1;
    }
}

/// With this

if ( ship.x - ship.width / 2 < 0 ) {
    ship.x = 0 + ship.width / 2;
    ship.rotation += 1;
}
if ( ship.x + ship.width / 2 > stage.stageWidth ) {
    ship.x = stage.stageWidth - ship.width / 2;
    ship.rotation += 1;
}
if ( ship.y - ship.height / 2 < 0 ) {
    ship.y = 0 + ship.height / 2;
    ship.rotation += 1;
}
if ( ship.y + ship.height / 2 > stage.stageHeight ) {
    ship.y = stage.stageHeight - ship.height / 2;
    ship.rotation += 1;
}