Air-breathing hypersonic powerplants are typically fighter-jet engine-sized. But Velontra has just test-run its surprisingly small Bronco hypersonic propulsion system.
Small-displacement turbocharged internal combustion engines can experience "knock" without suffering lasting damage. Knock happens when the fuel ignites earlier than expected. Much more damaging is "super-knock." Unlike normal knock, super-knock is caused by a detonation wave due to a feedback loop between the heat release associated with the flame and pressure inside an engine cylinder.