I had to look this thing up for myself and it is incredible, lmao.
The text:
Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run.
I love when you read experiments that go so delightfully fucking wrong that everyone involved is absolutely miserable and the idea never really gets explored again.
