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

Your ship is accelerating forever because you did not include code to slow it down! Example code to slow:

if key == "s" or key == "S"  then
f = true
debounce = false
while f and wait() and not debounce do
ship.BodyVelocity.velocity = ship.BodyVelocity.velocity - Vector3.new(10,0,0)