US scientists, for the first time, have built a detonation that’s fixed in space. This detonation that’s a standing wave was formed in a prototype engine and the researches say that a system like this might one day enable aircrafts to fly at up to 17 times the speed of sound.
Majority of the fires are deflagrations. This way of combustion forms a subsonic reaction wave as well as fuels a lot of our transport technology. However, you can get a way stronger and more efficient release of energy by a detonation. This kind of combustion creates supersonic shock waves fueled by energy release from closely paired chemical reactions. These waves travel at a lot of times the speed of sound, with those created by igniting a hydrogen-air power-mix, for example, often being on par with speeds of Mach 5.
This powerful energy release is hard to control and extremely unstable. But if harnessed, it could be conducted to reach hypersonic flight for future ultrahigh speed intercontinental and interplanetary travel on Earth. Estimates say that an engine working with a Mach 5 flow path, like the one formed by a hydrogen-air fuel mix, could allow vehicle speeds of Mach 6 to 17. That would enable you to fly from New York to London in only half an hour.
The detonation engine has three key concepts. Pulse detonation engines form recurrent explosions, whilst in a rotating detonation engine, detonations travel around a round channel with the shockwave from every setting off the following without topping. They’ve both been demonstrated before. The University of Central Florida and the US Naval Research Laboratory‘s researches now say they’ve demonstrated the third concept: a fixed or slanted detonation wave engine. Their results are reported in the Proceedings of the National Academy of Sciences.
Producing a continuous detonation that’s fixed in space, so that the ensuing shockwave is stable and stays in the same position is the idea behind a slanted detonation wave engine. “We want to feed [the detonation] with the right propellant mixture, at the right speed and freeze it in space,” Kareem Ahmed states.
Ahmed along with his colleagues manufactured a prototype engine called HyperReact (high-enthalpy hypersonic reacting facility) in order to create a detonation like such.
This device is separated into three segments. In the first, the mixing room, a jet of air and hydrogen is set aflame. This forms hot high-pressured air that runs into the following segment, the converging-diverging (CD) nozzle, that carries an axisymmetric square cross-section across all of its length. A jet of ultrahigh-purity hydrogen is added while the air enters the CD nozzle. Th CD nozzle’s shape is created to then speed up the combination to speeds of around Mach 4.5 while it enters the test segment. In the last room there’s a 30-degree rotating angle ramp.
It was discovered by the team that by manipulating the power mix, temperature and air flow through the rooms they were capable of creating an oblique shock on the ramp that formed a detonation that was balanced on the ramp. This fixed wave detonation carried on for the duration of active powering, which was around 3 seconds. This is notably longer than a regular detonation and shows proof-of-concept, said researches.
It’s explained by Ahmed that the key benefit of detonation based drive would be much higher efficiency than deflagration-based systems. “Achieving hypersonic speeds is critical because we don’t currently have a propulsion system that can do that,” he says. “The only propulsion system that can give you hypersonic speeds is a rocket motor. Now rocket motors are not efficient. We know that because otherwise we’d all be flying to outer space. They are very expensive.”