I was in an airplane with a new experimental hyper speed engine. The plane took off at normal speed, and then when it reached the appropriate altitude engaged the new engine. I knew even before the engine was engaged that something was wrong. I was standing at the back of the aircraft in the galley. I could feel the G forces against my body as the engines engaged, but the plane immediately began to lose control. It started to spin sideways and headed straight to the earth. The pilot tried to control the plane but was unable to recover. It slammed into the earth with incredible force; disintegrating the aircraft on impact.