My scripted Ship is moving and accelerating forever?

So I made a hopperbin, that will control a basic ship, I'm taking it easy and it only moves on the Z axis but, when 'W' is pressed, then released, the velocity keeps increasing. I know that a lot of this code is inefficient and messy, but I'm a beginner.

tool = script.Parent
player = tool.Parent.Parent.Character
playerc = player:getChildren()
for _,v in pairs(playerc) do
    if v:IsA("Part") then
        v.Touched:connect(function(hit)
            if hit:IsA("Seat")then
                ship = hit.Parent.ship
                function onKeyDown(key)
                    if key == "W" or key == "w" or string.byte(key) == 113 or string.byte(key) == 87 then
                        f = true
                        debounce = false
                        while f and wait() and not debounce do
                            ship.BodyVelocity.velocity = ship.BodyVelocity.velocity + Vector3.new(10,0,0)
                        end
                    end
                end
                function onSelected(mouse) 
                    mouse.KeyDown:connect(onKeyDown) 
                end 

                tool.Selected:connect(onSelected)
            end
        end)
    end
end