Video: Ejection seat test

No, that's not a real person flying out of this rocket sled flying down the track at 600 mph. It's a mannequin test of a new ejection seat system for the F-35 Lightning II fighter jet. From BAE Systems:

The system has been tested to its limits, as a full scale front section of the aircraft, complete with ejection seat and mannequin was launched at speeds in excess of 600 mph down a test track.  More than 30 ejection seat tests have been completed in the UK, France and the USA.  

Witnessing the final test which took place at Martin Baker's facility at Chalgrove Airfield in Oxfordshire, BAE Systems' Test Manager Rick Whittaker commented "Ejecting from an aircraft like F-35 typically takes no more than three seconds from the time the ejection handle is pulled to the pilot being on a parachute. You can imagine how quickly everything happens.  Incredibly, during the tests up to 900,000 measurements were recorded every second and I am pleased to say the systems performed really well."

"British Team Completes 600mph Ejection Tests for F-35 Aircraft"