Questions that have bedeviled legions of circus-goers and carnival connoisseurs: why doesn't the gunpowder kill the cannonballer before they exit the cannon? Do my eyes deceive me? And how can I break into the fast-growing field of human cannonballing? Patience, my friends. All in good time.
They don't actually use gunpowder
The "cannons" used by human cannonballers are actually giant catapults, and the smoke and explosions produced are just for show. The first human catapult act was performed in 1877, by a girl who was only 14 years old, using "elastic springs" to turn her into a living projectile. (She later went on to tour with P.T. Barnum.) The technology has changed a bit in recent years but the idea is the same: once a cannonballer clambers into his cannon, he stands on a platform about three-quarters of the way down the barrel. High-pressure compressed air is pumped into the chamber left between the platform and the bottom of the barrel, sending the platform to the top of the barrel -- and the cannonballer into the air.
Coming down is the hard part
Actually, plenty of human cannonballers do meet untimely ends on the job, but it's not usually the coming-out-of-the-cannon part that does it; according to Cecil "Straight Dope" Adams, of the 50 human cannonballers who'd had careers before the 1990s, 30 of them had been killed -- mostly by falling outside of the net. (Like this.) Dummy models are test-fired to help ensure a cannon's aim and accuracy, but the cannonballer himself has a big role to play -- there's a bit of mid-air acrobatics involved. You've got to turn just right in the air to ensure you land on your back rather than your neck.
The job's not for everyone
First of all, the pay's not great. Then there's the reality of having to live and travel with a circus, the romance of which wears of mighty fast, we'd imagine. Like most strange and unpleasant jobs, it's often passed on from parent to child: the Smith family, for instance, have been cannonballers for thirty years, despite the family patriarch's wish that he'd raised "doctors and lawyers" instead. (We get it: with the liabilities and injuries that come along with human cannonballing, free consultations from both couldn't hurt.)