You're more than 3.6 km (12,000 ft) above the Earth. And there's no turning back now. But as you jump out of the plane, and see how beautiful the Earth looks below you, you start to think that this might not be so bad. Then you pull the cord to open your parachute, and all your worst fears come true. There's no parachute coming out, and now you're plummeting towards the ground at about 200 km/h (125 mph). You've only got about a minute before you hit the ground. Is there anything you can do to save yourself?