Like medieval military engineers did before them, the NOVA
crew fine-tunes its attack using trial-and-error. Neel
believes that if the sling is shortened, it will add arc to
the stone's flight and give it more distance.
His hypothesis proves right: The next launch travels the right
distance but lands a few feet to the wall's right. They shift
the giant trebuchet just one inch to the left. This time they
are on line but just overshoot the wall. They pull the sling
in six inches and this time, it hits its mark.