Superfast drone fitted with new 'rotating detonation rocket engine' approaches the speed of sound

News
By Peter Ray Allison
published

Engineers have successfully flown a drone at near-supersonic speeds thanks to a new type of engine that burns like a rocket and could one day lead to hypersonic Mach 9 commercial flights.

Hypersonic rocket flies above the clouds
The drone, which resembled a rocket, flew 10 miles (16 km) at Mach 0.9 — over 680 miles per hour — using 80% of the engine's available thrust. This image is purely illustrative. (Image credit: Alexyz3d/Getty Images)

Venus Aerospace has completed the inaugural test flight of a drone fitted with its "rotating detonation rocket engine" (RDRE) — accelerating it to just under the speed of sound. The company wants to one day build superfast commercial jets using this new type of engine. 

In the test flight, conducted Feb. 24, the company flew the drone, which is 8 feet (2.4 meters) long and weighs 300 pounds (136 kilograms) to an altitude of 12,000 ft (3658 m) by an Aero L-29 Delfín plane, before it was deployed and the RDRE was activated, company representatives said in a statement. 

The drone flew 10 miles (16 km) at Mach 0.9 — over 680 miles per hour — using 80% of the RDRE’s available thrust. The successful flight proved the viability of RDRE and the associated onboard flight systems. Three weeks earlier, Venus Aerospace demonstrated the viability of its RDRE technology with a long-duration test burn — during which engineers showed their engine worked for the duration of this test flight.

Rather than using a continuous burn like most rocket engines, RDRE operates by a detonation wave continuously rotating around an annulus, or ring-shaped, chamber. The fuel, hydrogen peroxide, is injected into the annulus and the repeated detonations become self-sustaining after the initial ignition. In the RDRE test flight, the annulus was approximately 12 inches  (25.4 centimeters) in diameter and produced 1,200 pounds (544 kg) of thrust.

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The RDRE technology is 15% more efficient than conventional rocket engines, Venus Aerospace representatives said in a statement. As a result, an RDRE-propelled craft could theoretically travel farther on the same amount of fuel as conventional engines that combust fuel at constant pressure. Some have also theorized it could be as much as  25% more efficient than current technologies.

The successful test flight raises the odds of commercially viable supersonic flight. One of the long-term goals for Venus Aerospace is to develop a commercial supersonic aircraft that could travel at Mach 9 (over 6,800 mph) (11,000 km/h)

For comparison, the Concorde aircraft could fly at just over Mach 2 (just under 1,550 mph, or 2,500 km/h), while the forthcoming Lockheed SR-72 prototype is expected to fly at speeds greater than Mach 6 (approximately 4,600 mph, or 7,400 km/h). To put this into context, a vehicle flying at Mach 9 could travel from London to San Francisco in an hour. 

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Just as Concorde was noisy at take-off, the RDREs' constant detonations will make any craft fitted with them incredibly loud. And unlike conventional jet engines, which offer much smoother accelerations, the rapid, repeated cycles of acceleration from the continuous detonations may also cause increased stress and fatigue of the engines and associated support structures.

Because RDRE could have military applications, Venus Aerospace is also collaborating with the Defense Advanced Research Projects Agency (DARPA).

For now, Venus plans further test flights using drones One test flight engineers are considering involves fitting the current RDRE on a larger drone capable of achieving hypersonic flight — five times faster than the speed of sound (approximately 3,900 mph, or 6,200 km/h). 

Peter Ray Allison
Peter Ray Allison

Peter is a degree-qualified engineer and experienced freelance journalist, specializing in science, technology and culture. He writes for a variety of publications, including the BBC, Computer Weekly, IT Pro, the Guardian and the Independent. He has worked as a technology journalist for over ten years. Peter has a degree in computer-aided engineering from Sheffield Hallam University. He has worked in both the engineering and architecture sectors, with various companies, including Rolls-Royce and Arup.

2 Comments Comment from the forums
  • danr2222
    "The fuel, hydrogen peroxide..."
    H2O2, solus, is a low-Isp non-starter for any future development, and even as an oxidizer with a proper fuel in a bipropellant system. They're going to have either short range or rather oversized propellant tanks --> more mass, more drag, less payload. If missiles (or any other airframes) are going to be propelled by rocketry, the high-efficiency future will be in the direction of SpaceX' high-pressure-regime methalox engines, shrunk to scale. They already operate at detonation pressures, and a thermodynamic efficiency approaching theoretical limits.

    I suspect their use of peroxide is for its resistance to RDEs' notorious flameout instabilities. It's like a trick-candle that starts itself up again after you blow it out.

    RDEs waste space and increase mass, filling the core with metal just for the purpose of presenting a thin annulus to sustain the revolving shock front(s). That's volume that a conventional rocket engine chamber exploits to the max to get the greatest throughput (via the injector-populated back wall) for mass ejection and velocity out the freaking nozzle.
    Reply
  • Psychronizer
    danr2222 said:
    "The fuel, hydrogen peroxide..."
    H2O2, solus, is a low-Isp non-starter for any future development, and even as an oxidizer with a proper fuel in a bipropellant system. They're going to have either short range or rather oversized propellant tanks --> more mass, more drag, less payload. If missiles (or any other airframes) are going to be propelled by rocketry, the high-efficiency future will be in the direction of SpaceX' high-pressure-regime methalox engines, shrunk to scale. They already operate at detonation pressures, and a thermodynamic efficiency approaching theoretical limits.

    I suspect their use of peroxide is for its resistance to RDEs' notorious flameout instabilities. It's like a trick-candle that starts itself up again after you blow it out.

    RDEs waste space and increase mass, filling the core with metal just for the purpose of presenting a thin annulus to sustain the revolving shock front(s). That's volume that a conventional rocket engine chamber exploits to the max to get the greatest throughput (via the injector-populated back wall) for mass ejection and velocity out the freaking nozzle.
    (sigh)...I would have thought it was quite obvious that this is VERY preliminary, they've hardly even got the physics down yet, a concurrent number of rotating detonation wave-fronts hold the promise of superior efficiency because it IS a detonation, NOT a deflagration, this may surprise you, but, they actually know what they are doing. Trust me, you are a few orders of magnitude in the weeds here, to put it politely, which I'm usually not when I read stuff like this...
    Reply