Popular Mechanics:

The last thing a fighter pilot wants to do is eject, and it’s not just because they’re abandoning the ship to a fiery demise. The turbulent process of ejecting puts pilots at serious risk of injury. Once those rockets fire under the seat, they blow a person up and out of the cockpit with enough force to seriously bruise both shoulders on the harness straps and possibly break collarbones. And you better tuck in your knees and elbows, because if anything hits the side of the cockpit on the way out, it’s coming off.

Not that any of us would ever be in this situation but it’s still fascinating. The post includes some incredible video of pilots ejecting, including one from a plane already on the ground.