Originally invented by iconic stuntman Hal Needham, the nitrogen-powered straight fire cannon is an essential tool for modern vehicle stunts. They're often used in film and television, for shots considered too dangerous to be performed by actual stunt drivers. It works on the same principle as a toy pop-gun—using air pressure as the propellant, rather than combustion.
The cannon also comes in a miniaturised version designed to launch cars into barrel rolls, rather than swan dives. For those maneuvers, the pneumatic tube is replaced with a pneumatic piston that's installed in the car itself. When activated, piston punches downward, causing the car to flip. The record-setting Aston Martin crash from Casino Royale was accomplished with just such a device.
"We managed seven-and-three-quarter turns." Gary Powell, professional stunt driver, told the Sun. "And it was more difficult than it sounds because the Aston is built so well that it wouldn't turn over from a ramp. We had to put a nitrogen air cannon in the car to make it flip and the director, Martin Campbell, wanted the shot done in one take."