“我们希望冻结空间和利用,energy. Rather than it destroying buildings, as you saw in Lebanon, now I want to use it and produce thrust with it," Ahmed told Live Science. "If we can do that, we can travel super fast."
When a mixture of air and fuel detonates in this way, the resulting combustion is extra efficient as close to 100% of the fuel is burned. The detonation also generates a lot of pressure, which means the engine can generate much more thrust than other approaches. In theory, this detonation should be able to propel an aircraft at up to 17 times the speed of sound, say the researchers, which could be fast enough for spacecraft to simply fly out of the气氛，而不是需要在火箭上挂起电梯。
The challenge is sustaining the detonation for long enough to power such flight, and previous experimental demonstrations have topped out at just a few milliseconds. The main difficulty, Ahmed said, lies in preventing the detonation from traveling upstream toward the fuel source, where it can cause serious damage, or further downstream, where it will fizzle out.
To see if they could improve on the previous record, Ahmed and his colleagues built a roughly 2.5-foot-long (0.76 meters) series of chambers that mixes and heats air and氢气气体在加速它到超音速速度并在斜坡上射击它。
经过carefully balancing the proportions of the air-fuel mixture, the speed of the gas flow and the angle of the ramp, they were able to generate a detonation that remained fixed in position for around 3 seconds. That's long enough to confirm that the detonation was stabilized in a fixed position and was not travelling up or downstream, Ahmed said, which is a first, major step toward realizing a real-life ODWE.
Frank Lu, a professor of mechanical and aerospace engineering at the University of Texas at Arlington who specializes in detonation-based engines, said demonstrating stable detonation is a significant achievement. To develop a practical engine researchers will now have to work out how to operate over a range of speeds and altitudes and deal with combustion instabilities caused by things like uneven mixing of the fuel and air.
"I think the investigators have done an excellent job and look forward to further results," Lu told Live Science.
And promisingly, Ahmed said the structure of the test apparatus is not that different from the design of a full-scale ODWE. The main challenge for the researchers now is working out how they can alter the three key ingredients of fuel mix, air speed and ramp angle while still maintaining the stability of the detonation.