Engineers have developed a new kind of engine that could make rockets much easier to build – but it’s very unstable.
In more than half a century since humans first walked on the moon, little has changed in the area of space propulsion. Existing rocket engines – such as the ones that brought NASA’s Space Shuttle into orbit – required more than 1.5m kg of chemical fuel, which is 15 times heavier than a blue whale.
Now, however, researchers from the University of Washington have designed a new rocket engine concept that could potentially bring propulsion into the 21st century. Writing in Physical Review E, they said this new engine – referred to as a rotating detonation engine – would not only make rockets more fuel-efficient, but also more lightweight and less complicated to construct.
The only problem is that – as the name suggests – the engine is just too unstable to be used in an actual rocket.
But with a mathematical model now developed, which can describe how this engine could work, engineers can design tests to improve these engines and make them feasible for use.
“The rotating detonation engine field is still in its infancy. We have tons of data about these engines, but we don’t understand what is going on,” said lead author James Koch.
“I tried to recast our results by looking at pattern formations instead of asking an engineering question – such as how to get the highest performing engine – and then boom, it turned out that it works.”
A conventional rocket engine works by simply burning propellant and pushing it out the back. In a rotating detonation engine, however, propellant flows between a series of concentric cylinders.
After ignition, the rapid heat release forms a shockwave; a strong pulse of gas with significantly higher pressure and temperature that is moving faster than the speed of sound.
‘It’s so violent’
Working in this engine’s favour is that, unlike a conventional engine that requires a lot of machinery and moving parts, the new engine’s shockwave directs and controls the propulsion naturally.
“The downside of that is that these detonations have a mind of their own. Once you detonate something, it just goes. It’s so violent,” Koch said.
Using an experimental version of the engine, the researchers recorded a series 0.5 second combustions using a high-speed camera. With these observations, they could develop the mathematical model of the engine.
“I have identified the dominant physics and how they interplay. Now I can take what I’ve done here and make it quantitative,” Koch said. “From there we can talk about how to make a better engine.”