local function rockspeed ()
local lastspeed = 0
while (true) do
	local sx,sy,sz = Spring.GetUnitVelocity (unitID)
	if (sx and sy and sz) then
		local speed = (math.abs (sx)+ math.abs (sy) + math.abs (sz))*10
		local speeddiff = speed - lastspeed
		if (speeddiff < -3) then 
			Spring.Echo ("unit " .. unitID .. " slowing down " .. speeddiff)
			Turn (body, x_axis, math.rad(20), math.rad(180))
			WaitForTurn (body, x_axis)
		
		else if (speeddiff > 3) then 
			Turn (body, x_axis, math.rad(-20),math.rad(180))
			WaitForTurn (body, x_axis)
			Spring.Echo ("unit " .. unitID .. " going faster" .. speeddiff) 
		else
		Turn (body, x_axis, 0,math.rad(360))
		WaitForTurn (body, x_axis)
		end
		end
	lastspeed=speed
	end
	Sleep (100)
	end
end