Human cannonballs, like most thrill acts, mostly do their stunts for the fame and glory. But sometimes, because of the trauma exerted by the cannon, stardom comes at a steep price.
In order to withstand the physical demands of the act, cannonballs have to stay in shape. Weightlifting and cardiovascular workouts help them maintain strong back, knee and core strength. Inside the cannon, they clench their bodies to stay as rigid as possible during the blast, which accelerates a cannonballer's body to top speed in about one-fifth of a second [source: The Star].
That kind of acceleration may subject them to a force of 9Gs during launch and around 12Gs at impact -- that's nine and 12 times the force of gravity, respectively. Without a good amount of body strength, G-forces can cause some people to lose consciousness, meaning there's no way for the ground-bound body to control its movements.
A conscious flyer keeps his or her eyes open to find the net, and conducts a well-timed somersault that creates a relatively soft, back-first landing, with the chin tucked tightly toward the chest. Human cannonballs aim for the back third of the net, which absorbs their forward energy but also bounces them back a good distance -- come up short on the net, and the cannonball will hit the ground on the rebound.
Sometimes, though, cannonballers overshoot their targets. One famous cannonball is Elvin Bale, the "Human Space Shuttle," who toured with the Ringling Brothers and Barnum & Bailey circuses in the 1970s and 1980s. When he set up for one show, he calibrated the cannon using his test dummy, which, unbeknownst to him, had been saturated with water. This made it heavier than normal. As a result, the cannon sent him flying past his airbags, and he ended up paralyzed in both legs.
Sometimes, things go awry in the most terrible way imaginable. In April 2011, a fledgling stuntman named Matt Cranch was executing one of his first shots for the Scott May Stunt Show in England when, just after blastoff, the net collapsed. Cranch landed on his head in front of hundreds of horrified spectators and died shortly thereafter.
For human cannonballs, though, danger is a necessary and appealing part of the show. Without the constant threat of ruinous injury or death, their acts draw no acclaim. So, in spite of the risks, they press on, slipping themselves into the cramped, dark barrels of cannons, waiting to touch the skies and the hearts of their adoring onlookers.