Endless detonation could be the key to hypersonic flight and space planes that can seamlessly fly from orbiting Earth. And now, researchers have recreated the explosive phenomenon in the lab that could make it possible.
Detonations are a particularly powerful type of explosion that travel outward faster than the speed of sound. The massive explosion that rocked the port of Beirut in Lebanon last August was a bang, and the widespread destruction it caused demonstrates the tremendous amounts of energy they can produce.
Scientists have long dreamed of building aircraft engines capable of harnessing this energy; such a craft could theoretically fly from New York to London in less than an hour. But the bangs are incredibly difficult to control, and typically last less than a microsecond, so no one has been able to make it a reality yet.
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Now, a team from the University of Central Florida has created an experimental setup that allows them to hold a detonation in a fixed position for several seconds, which the researchers say is a major step towards future hypersonic propulsion systems.
“What we’re trying to do here is control that detonation,” said Kareem Ahmed, associate professor of mechanical and aerospace engineering at the University of Central Florida and lead author of a new research paper released Monday. (May 10) in the journal Proceedings of the National Academy of Sciences.
“We want to freeze it in space and harness that energy. Rather than destroying buildings like you saw in Lebanon, I now want to use it and produce a push with it,” Ahmed told Live Science. . “If we can do that, we can travel really fast.”
The breakthrough was built on decades of research into a theoretical propulsion system called the Oblique Detonation Wave Motor (ODWE). The concept works by channeling a mixture of air and fuel at hypersonic speeds (more than five times the speed of sound) down a ramp, which creates a shock wave. This shock wave quickly heats the air-fuel mixture and detonates it, causing the exhaust gases from the rear of the engine to explode at high speed. The result? Lots of push.
When a mixture of air and fuel explodes in this way, the resulting combustion is extremely efficient as almost 100% of the fuel is burned. Detonation also generates a lot of pressure, which means that the engine can generate a lot more thrust than other approaches. In theory, this detonation should be able to propel an aircraft up to 17 times the speed of sound, the researchers say, which could be fast enough that spacecraft can simply fly out. atmosphere, rather than having to hitch an elevator on rockets.
The challenge is to sustain the detonation long enough to propel such a flight, and previous experimental demonstrations have passed in milliseconds. The main difficulty, Ahmed said, is to prevent the detonation from spreading upstream to the fuel source, where it can cause serious damage, or further downstream, where it will go out.
“There’s always been the question of, ‘Well, if you hold it for a millisecond or so, have you just held it temporarily? “Ahmed said.
To see if they could improve on the previous record, Ahmed and his colleagues built a series of chambers about 2.5 feet long (0.76 meters) that mix and heat the air and hydrogen gas before accelerating it to hypersonic speeds and pulling it up a ramp.
By carefully balancing the proportions of the air-fuel mixture, the speed of the gas flow, and the angle of the rail, they were able to generate a detonation that remained stationary in position for approximately 3 seconds. This is long enough to confirm that the detonation was stabilized in a fixed position and was not moving upstream or downstream, Ahmed said, which is a major first step towards achieving an actual ODWE.
Frank Lu, professor of mechanical and aerospace engineering at the University of Texas at Arlington, specializing in detonation engines, said demonstrating a stable detonation was a significant achievement. To develop a practical engine, researchers will now need to figure out how to operate over a range of speeds and altitudes and deal with combustion instabilities caused by things like an uneven mixing of fuel and air.
“I think the investigators have done a great job and look forward to further results,” Lu told Live Science.
The researchers only conducted their experiment for a few seconds, mainly because the intensity of the detonation quickly erodes the glass walls of the test chamber, Ahmed explained. They had to use glass in their initial tests in order to be able to perform optical measurements of the detonation, but if they were to replace them with metallic sides, they should be able to make the detonation work much longer, he said. .
And promisingly, Ahmed said that the structure of the test apparatus is not that different from the design of a full-scale ODWE. The main challenge for researchers now is figuring out how they can alter the three key ingredients of fuel mixture, air speed, and ramp angle while maintaining the stability of the detonation.
“Now we’ve shown that it’s doable, it’s more of an engineering problem to explore how to keep it on a larger area of operation,” Ahmed said.
Originally posted on Live Science.