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By:

Commodore S.L. Deshmukh

31 October 2024 at 8:30:19 am

The Detonation Race Is On

Rotating detonation engines could redefine propulsion in the near future, and India cannot afford to be a bystander For more than a century, the basic architecture of the jet and rocket engine has remained remarkably resilient. Fuel is burned, gases expand and turbines, compressors or other components turn that energy into thrust. Now, a different idea is beginning to move from laboratories towards operational propulsion: the rotating detonation engine (RDE). It replaces conventional...

The Detonation Race Is On

Rotating detonation engines could redefine propulsion in the near future, and India cannot afford to be a bystander For more than a century, the basic architecture of the jet and rocket engine has remained remarkably resilient. Fuel is burned, gases expand and turbines, compressors or other components turn that energy into thrust. Now, a different idea is beginning to move from laboratories towards operational propulsion: the rotating detonation engine (RDE). It replaces conventional combustion with a continuously travelling supersonic detonation wave, promising greater efficiency in a smaller and mechanically simpler package. If propulsion is a contest between how much energy can be extracted from fuel and how little machinery is required to do it, RDEs have an intriguing advantage. An RDE works inside an annular, or ring-shaped, combustion chamber. Fuel and oxidiser are injected into the chamber and ignited. Instead of a conventional flame moving relatively slowly through the mixture, a detonation wave races around the chamber at supersonic speed. The wave compresses and ignites fresh fuel as it travels, creating a self-sustaining cycle. The resulting high-temperature gases are expelled axially, generating continuous thrust. Improving Fuel Efficiency That is fundamentally different from the combustion process used by traditional engines. Conventional gas-turbine engines operating on the Brayton cycle rely on subsonic deflagration - a rapid burning process in which the flame front travels through the combustible mixture at less than the speed of sound. RDEs generally operate on the Humphrey cycle, using pressure-gain combustion to extract more useful energy from the chemical reaction before the gases are expelled. Detonation-based combustion has the potential to improve fuel efficiency by as much as 25 percent compared with conventional engines. RDEs can also dispense with some of the heavy and complicated moving machinery associated with traditional propulsion systems. That creates the possibility of engines that are smaller, lighter and easier to manufacture. For missiles and rockets, where every kilogram matters, such advantages are particularly valuable. The appeal extends beyond efficiency. A continuously propagating detonation wave can provide steady thrust while eliminating the need for a conventional turbine-compressor architecture. The result could be a propulsion system suited to hypersonic missiles, high-speed aircraft, space vehicles and other platforms where compactness and performance matter as much as raw power. That said, maintaining a smooth and stable detonation wave is extraordinarily demanding. Fuel injection must be precisely controlled and the geometry of the combustion chamber carefully engineered. The number, spacing and shape of injectors can determine whether the detonation remains stable or breaks down. Inside the chamber, extreme temperatures and pressures place enormous demands on engine walls, requiring advanced cooling systems and high-performance materials. These engineering problems explain why the RDE revolution has been promising for years without yet becoming routine technology. The challenge is no longer simply demonstrating that a detonation can be sustained. It is turning that phenomenon into a reliable, durable and flight-ready propulsion system. Production Race The United States is pushing ahead on several fronts. NASA has successfully tested full-scale RDEs producing more than 5,800 pounds of thrust and is planning to raise that figure to 10,000 pounds for potential lunar and Mars missions. Pratt & Whitney, part of RTX, has conducted extensive RDE testing for military applications, exploring high-speed and long-range propulsion with a simpler architecture. DARPA is pursuing RDE technology for hypersonic standoff missiles under its Gambit programme, while L3Harris has conducted long-duration, full-scale tests aimed at advancing next-generation missile propulsion. The international competition is broader still. Japan’s JAXA, GE Aerospace and Chinese institutions have been pursuing RDE applications in rockets and hybrid air-breathing engines, including systems intended for hypersonic flight. China, in particular, is treating the technology as part of its broader push towards high-speed aerospace and military systems. Researchers at Tsinghua University introduced a hybrid design in 2024 combining a ramjet with a rotating rotor compressor, intended to improve starting at lower speeds and enhance performance during flight. In 2025, scientists at the Beijing Power Machinery Research Institute reportedly completed a milestone test of an RDE operating steadily for 180 seconds at Mach 6.3. Recent Chinese test engines have also reportedly incorporated specialised materials capable of tolerating internal temperatures of up to 2,500°C. For India, therefore, RDEs are no longer merely an interesting engineering experiment but are fast becoming part of the strategic propulsion race. India has already taken an important step. Defence propulsion start-up D-Propulse, incubated at IIT Madras, has demonstrated what it describes as the country’s first indigenous 5 kN air-breathing RDE coupled with an aerospike nozzle. The hot-fire demonstration was conducted at a DRDO test facility and reportedly achieved Technology Readiness Level-5 validation in the specified environment. That matters because it represents a movement from laboratory research towards an integrated propulsion prototype. D-Propulse has stated that it is targeting a flight-ready engine by December 2027. The company says its technology can deliver 15–25 percent higher thermodynamic efficiency than conventional air-breathing propulsion systems and can be produced through precision machining rather than complex turbine assemblies, potentially reducing both production costs and lead times. The applications could be considerable. Defence systems could include hypersonic missiles, air-to-air and air-to-ground weapons and compact propulsion systems for standoff strike platforms. In space, RDEs could find uses in upper-stage rocket engines, planetary landers and deep-space propulsion, where higher efficiency and lower engine mass are particularly valuable. The technology could even migrate beyond aerospace: RDE-based gas turbines could potentially generate electricity with greater thermal efficiency and lower fuel consumption. The larger significance is that propulsion technology often determines what a country can build, how far it can travel and how quickly it can respond. RDEs remain an emerging technology, and their promise should not be confused with operational maturity. But countries that solve the problems of stability, materials, cooling and reliable fuel injection first could gain an important advantage in the next generation of aerospace and defence systems. (The writer is a retired naval aviation officer and a defence and geopolitical analyst. Views personal.)

Warriors of Night

Updated: Oct 22, 2024

We name our daughters Durga, Lakshmi and Saraswati; we worship the divine feminine power in the temples but oppress, repress and even attack the feminine power amidst us. That is the irony in the way India sees its women.

After the safety of the daylight fades, women are seen as easy prey by the predators of the night.

We mark the nine nights of Navratri, the festival of the goddess, by celebrating the dedication and valour of nine real-life women who brave the challenges of the night to pursue their dreams.


Part - 4


Never felt unsafe

The singer says there has been a generational change over the last two decades

Never felt unsafe

Work has no timings for Aisha Sayed. Sometimes, she begins her studio recording at 12 AM and finishes by 5 AM; at other times, concerts and live shows start at 9 AM and she’s done by midnight. In her field of work as a performer and singer, Sayed is used to not getting a night’s sleep and often returning home when most of the city is set to wake up. “I have been travelling at night but I have never, ever, felt unsafe in Mumbai,” says the singer-performer who began her career at the age of 13 years. Her father spotted her talent for music and took her to meet a sound engineer who was their neighbour in Bandra. The family helped her get opportunities and from there, her career began.

Being among the top contenders in Indian Idol, season 3, in 2007 catapulted her to fame and it opened up a world of new performance opportunities across the country. “I was just 20 years then and I was travelling the world, performing at the most lavish weddings, staying at the most luxurious hotels and performing at big corporate gigs,” she says. Safety, while on work, is has never been an issue for her for the organizers arrange a security detail for the performers. “They escort us until we reach the room. And since we travel with our team in a big group, there is always safety in numbers,” says Sayed, who sings in 10 languages. Her peers have faced instances of audience members being rowdy. “Once in Delhi, a group of drunk men followed my colleague to her room and kept banging on her door late into the night. But I have been fortunate,” she says.

Work assignments have taken to varied places, from the most luxurious international destinations to far-off venues in the hinterland of India where she’s travelled through dark, dense forested areas. “I have driven through areas where the only light is that of your car’s headlights. Turn around and you see pitch darkness,” says Sayed. She’s always got a little prayer on her lips when travelling through these remote areas for miles together. She recalls a show in Chattisgarh where she had to travel for nine hours at a stretch through remote and forested areas. “No place in our country is as safe as Mumbai,” she stresses. She would know, considering her extensive travels. She advises women to travel in groups while in places that are unfamiliar or unknown and never to venture out at night alone. “Keep your family informed of your whereabouts,” she says.

While her agreements state that proper security at all times, Sayed says that she drives her own car if she’s out at night for parties or personal work but insists that the people of Mumbai are largely helpful and cooperative. A rickshaw driver who once drove to home in the wee hours of the night, after a recording, waited at her gate until the watchman let her in. Friends and colleagues have dropped her home several times.

Mumbai, she feels, has changed—and it’s for the better, in the past two decades. “Earlier, on buses and trains, men would use the crowd as an excuse to touch women inappropriately. That has gone down. There is a generational change that I see,” says Sayed. She used to take the BEST buses and trains to her training classes and for recordings in the early days of her career.

Her timings are inconsistent and her shows take her to various cities and towns. But the Mumbai-bred girl emphasizes that her city is very safe for women, despite the various incidents of violence. “Mumbai is the only place where a woman can wear what she wants, wear bright red lipstick, leave her hair open and look glamorous and still be safe.”

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