The circus stunt in which a person is propelled into the air from a cannon or some other contraption began in the early 1870s when a human cannonball was sent up only a short distance and was caught by an assistant on a trapeze bar. When the Zacchini family revived the stunt in 1922, they decided to make more daring flights by having the performer fly through the air and land in a net. Their first cannons depended on springs to propel the performer, but by 1927 compressed air was put to work.

Striving to increase the excitement of the stunt, the family began to send the performer over Ferris wheels. They started with one Ferris wheel, but by 1939 or 1940 they reached the limit of even unreasonable safety when Emanuel Zacchini soared over three Ferris wheels and through a horizontal distance of 70 meters.

The human cannonball act is probably one of the most impressive acts of projectile motion, for it obviously involves the chance that the performer might miss the net. Are more subtle dangers involved?

Answer To get ready for a shot, the performer would slip his or her legs down inside “metal trousers” on the piston inside the barrel of the cannon. The trousers were fitted closely to the shape of the legs and were needed to supply support when the piston was suddenly shoved upward. The subtle danger involved that shove, because the acceleration required for a long flight was so severe that the performer would momentarily black out. Part of a performer’s training was to regain awareness during the flight so that a controlled roll could be made on the net. If the landing were uncontrolled, then the collision and rebound on the net could easily break the limbs or neck of the performer. The family claimed that the muzzle speed of a performer was as much as 600 kilometers per hour, but a speed of less than 160 kilometers per hour seems more credible.

Another subtle danger lay in the air drag encountered by a performer. The size of the air drag depended on the orientation of the body as it flew through the air: It was smaller if the body was oriented along the direction of travel, and larger if the body was oriented perpendicular to that direction (which might happen during the descent). A smaller air drag increased the range of the shot; a larger air drag reduced the range. Because the performer’s orientation varied from shot to shot, someone had to calculate (or guess) approximately how far the performer would go and then make the net wide enough to account for the possible variations due to the air drag.