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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.)

India’s Dilemma: The Specter of a Three-and-a-Half-Front War

Updated: Jan 2, 2025

In the first of a two-part series, we examine India’s growing security challenges, both internal and external, and the strategic steps needed to navigate these complexities

India’s Dilemma

The world is a powder keg. Unrest in Iran, Iraq, Israel, Syria, and across the Middle East coincides with the protracted war between Russia and Ukraine. These crises ripple across borders, leaving no country untouched. For India, the stakes are particularly high. In Asia, tensions with Bangladesh and Pakistan, coupled with an unresolved standoff with China, exacerbate an already precarious security environment. Adding fuel to the fire, domestic challenges further intensify the risks, raising the alarming possibility of what strategists dub a “three-and-a-half-front war.”


India’s geographical location offers both an advantage and a disadvantage. Strategically positioned as a hub for global logistics, the country is critical to ensuring regional stability. Yet, its proximity to two longstanding adversaries—China and Pakistan—complicates matters. Bangladesh, with its shifting allegiances, has added a new dimension to this calculus. The volatile domestic situation, marked by communal and political unrest, completes the trifecta, with internal challenges forming the “half front” in this ominous scenario.


Indo-China relations have long tested India’s diplomatic mettle. For decades, China has pursued a strategy to keep India on edge, using a mix of psychological and military provocations. Rooted in its desire to avenge the ‘Century of Humiliation,’ China’s worldview is deeply shaped by a need to dominate its regional neighbours.


India’s rapid ascent on the global stage poses a direct challenge to China’s ambitions of regional and global supremacy. Beijing views New Delhi’s rising stature with unease, particularly its growing influence in the Indo-Pacific, its robust infrastructure along contested borders and its leadership in multilateral forums like the Quadrilateral Dialogue (QUAD). The refusal to join initiatives like the Belt and Road Initiative (BRI) and the Regional Comprehensive Economic Partnership (RCEP) has further strained ties.


The 2020 Galwan Valley clash, a tragic flashpoint in Indo-China relations, epitomized China’s aggressive designs. Beijing’s displeasure with India’s border infrastructure development and its closer ties with Western allies has only fuelled its belligerence. Militarily, China holds the upper hand, leveraging its advanced arsenal against India’s aging defence systems. This disparity emboldens Beijing to test India’s resolve repeatedly, creating a perpetual state of tension.


Beyond its direct provocations, China’s deepening ties with South Asia complicate India’s security calculus. Bangladesh, once a trusted ally, now edges closer to Beijing. Economic investments through the Belt and Road Initiative, strategic military partnerships, and increased political engagement hint at a significant shift in Dhaka’s priorities. While India continues to invest in its ties with Bangladesh, the growing influence of China in the region presents challenges that are impossible to ignore.


Since Partition in 1947, India and Pakistan have shared an acrimonious relationship. Pakistan’s grievances, from the creation of Bangladesh to its inability to annex Kashmir, have defined its hostile posture toward India. While India’s economic growth and diplomatic successes have widened the gulf, Pakistan continues to rely on asymmetric warfare through state-sponsored terrorism.


India has responded firmly with cross-LoC strikes and diplomatic efforts like pushing Pakistan onto the FATF grey list. However, Islamabad’s deepening ties with Beijing, including advanced weapon supplies, have strengthened its military, forging a troubling China-Pakistan nexus. This partnership, with potential strategic collaboration in Siachen and Ladakh, poses a serious challenge to India, raising concerns of a coordinated assault from both adversaries.


Bangladesh, once a close ally, now emerges as a wildcard in India’s security landscape. While the two countries share historical ties rooted in India’s role during Bangladesh’s liberation, recent developments suggest a drift. Dhaka’s growing economic partnership with Beijing and its reluctance to fully endorse India’s regional leadership underscore this shift.


China’s significant investments in Bangladesh’s infrastructure, ranging from ports to power plants, mirror its strategy in other South Asian countries. For India, this growing influence represents not just an economic challenge but a strategic one. The possibility of Bangladesh aligning with China in regional disputes adds another layer to India’s external threats.


The Domestic ‘Half Front’

India’s security challenges are compounded by internal issues like communal tensions, political polarization, and insurgencies in Kashmir and the Northeast, which strain resources and create exploitable vulnerabilities. Kashmir remains a flashpoint, with unrest offering Pakistan opportunities to stoke proxies, while Northeast insurgencies require constant vigilance. To counter the threat of a coordinated three-front assault, India must recalibrate its security policy with investments in defence modernization, strong alliances, and diplomatic finesse.


Modernizing the armed forces, with a focus on indigenization and reducing dependence on foreign suppliers, is imperative. Simultaneously, India must strengthen its regional partnerships, leveraging platforms like the QUAD and the Indian Ocean Rim Association to counterbalance China’s influence. Engaging with Bangladesh to rebuild trust and counter Beijing’s narrative will be equally crucial.


A united and resilient nation is less susceptible to external manipulation, ensuring that the ‘half front’ does not become a full-blown crisis. The challenges are formidable, but so too is India’s resolve.


(The author is a retired Indian Naval Aviation Officer and a geo-political analyst.


(In Part Two tomorrow, we focus on Bangladesh’s potential to emerge as a third front in the conflict, explore how India’s domestic situation constitutes a ‘half front’ and examine key remedial measures India must adopt to mitigate the threat)

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