The transformation of India's indigenous Kaveri jet engine program represents one of the most significant pivots in the country's aerospace development history. After decades of struggling to power manned fighters, the Kaveri Derivative Engine (KDE) has found new purpose as the propulsion system for India's stealth unmanned combat aerial vehicle (UCAV) platform, marking a critical milestone in achieving indigenous defence capabilities.

The Gas Turbine Research Establishment (GTRE) has achieved a significant milestone by successfully conducting a performance test of the Kaveri Dry Engine (KDE) with unrestricted throttle movement. This important test demonstrated the engine's ability to operate smoothly across its full throttle range without restrictions, a critical factor for ensuring responsive and reliable thrust control required in active flight operations.

The KDE, which is a dry (non-afterburning) derivative of the indigenous Kaveri turbofan engine, is designed to produce approximately 46 to 49 kN of dry thrust. Recent developments and tests show the engine now approaches the upper end of this range, with ground trials confirming thrust outputs close to 49-50 kN.

The unrestricted throttle test validates that the engine’s control and fuel delivery systems can maintain stable combustion and performance across all throttle settings, enhancing operational flexibility for various flight conditions.

The Rebirth Through Unmanned Aviation

The Kaveri program's resurrection centres on the development of a specialised derivative engine tailored for India's stealth combat aerial platform, designated for deep-strike, precision-guided, high-risk missions.

Unlike the original afterburner-equipped variant designed for the Light Combat Aircraft (LCA) with its 85 kilonewton thrust requirement, the unmanned aerial vehicle operates as a subsonic platform requiring no afterburner and functioning with 49kN thrust coupled with advanced digital controls. GTRE director SV Ramana Murthy explains that this fundamental difference—the absence of an afterburner requirement—provides the stealth dimension that distinguishes it from fighter aircraft engines, earning it the designation as a "derivative engine or dry engine".

The UCAV project, sanctioned in 2018, demonstrates remarkable technical maturity with 75 percent commonality with the original Kaveri engine. The platform targets ambitious operational parameters including Mach 0.9 speed capabilities, service ceilings up to 13,000 meters, and two-hour endurance specifications.

Current development efforts focus on the KDE configured for the 13-ton Ghatak stealth UCAV, with thrust output specifications ranging from 50-55 kN and potential upgrades reaching 60 kN. The engine incorporates advanced materials and improved compressor and turbine designs that address earlier development shortcomings while leveraging lessons learned from partnerships with France's Safran and Russia's NPO Saturn.

The Ghatak UCAV itself features impressive specifications including a maximum take-off weight of approximately 13 tonnes, service ceiling capabilities between 30,000-40,000 feet, operational range exceeding 1,000 kilometres on internal fuel, and subsonic cruising speeds of approximately Mach 0.8.

Future Engine Development Pathways

The cumulative investment in the Kaveri program since its 1983 inception totals approximately a paltry $239 million (nearly ₹2,000 crore at current exchange rates), representing modest expenditure compared to international engine development programs.

For comparative context, the Eurofighter Typhoon's Eurojet EJ200 engine required $1.6 billion for development from 1985 to 1995, while the Dassault Rafale's Snecma M88 cost $1.6 billion through initial testing phases in 1989. The Pratt & Whitney F135 for the F-35 Lightning II demanded $6.7 billion in development costs, while China has invested a staggering $42 billion in aero engine development programs.

The success of the KDE has catalysed ambitious future development programs, with GTRE pursuing next-generation propulsion systems for sixth-generation fighter applications.

The organisation is developing a 120kN thrust engine for fifth-generation fighters, with technologies representing several advancement levels beyond fourth-generation capabilities in thrust-to-weight ratios, turbine temperatures, and operational life specifications exceeding 2,000 hours. This development pathway includes potential collaboration with international engine houses such as Safran, Rolls-Royce, and General Electric for advanced technology transfer and joint development arrangements.

The sixth-generation engine development program specifically targets the Advanced Medium Combat Aircraft (AMCA) MK-2 variant, with specifications including a planned Turbine Entry Temperature of 2100 Kelvin, positioning it in the elite category of the world's most advanced power-plants. This high-temperature operation capability directly translates to superior engine performance, potentially allowing India to surpass decades of Chinese progress in jet engine technology, particularly when compared to the WS-15 engine designed for China's J-20 stealth fighter.

Supporting infrastructure development includes the near-completion of GTRE's 130kN Twin Engine Test Bed Facility in Rajankunte, Bangalore, with construction beginning in September 2023 and full operational capability expected by October 2025.

K Rajalakshmi Menon, Director General of aeronautical systems at DRDO, emphasizes that successful collaboration requires equal partnership capabilities, noting that India has achieved a maturity level where international engine houses have evaluated and assessed Indian capabilities, recognizing the country's readiness to undertake higher engine capability design and development programs. This recognition positions India as a credible partner in advanced aerospace technology development, essential for achieving the strategic autonomy that demands technological independence.

The Kaveri program's transformation from perceived failure to renewed relevance exemplifies the long-term value of sustained research and development investment in critical technology domains.

As the KDE variant approaches certification for the Ghatak stealth UCAV and derivative applications expand across naval and ground vehicle platforms, the program demonstrates that indigenous technological development, while requiring patience and persistence, ultimately provides the foundation for strategic autonomy and reduced dependence on foreign suppliers in critical defence capabilities.

Based On The Week Report