One of the most important turning points in India’s history of aerospace development is the metamorphosis of its own Kaveri jet engine program. The Kaveri Derivative Engine (KDE), which has struggled for decades to power manned aircraft, has found a new purpose as the propulsion system for India’s stealth unmanned combat aerial vehicle (UCAV) platform. This is a significant step towards developing indigenous defense capabilities.
The successful completion of a performance test of the Kaveri Dry Engine (KDE) with unfettered throttle movement marks a major milestone for the Gas Turbine Research Establishment (GTRE). This crucial test showed that the engine could run smoothly and unhindered across its entire throttle range, which is essential for guaranteeing the responsive and dependable thrust control needed for active flight operations.
The native Kaveri turbofan engine’s dry (non-afterburning) derivative, the KDE, is intended to provide between 46 and 49 kN of dry thrust. The engine is presently approaching the top end of this range, according to recent testing and developments; ground trials have confirmed thrust outputs that are close to 49–50 kN.
The unrestricted throttle test improves operational flexibility for a range of flight scenarios by confirming that the engine’s control and fuel delivery systems can sustain steady combustion and performance throughout all throttle settings.
The revival of the Kaveri program is focused on creating a specialized derivative engine for India’s stealth combat aviation platform, which is intended for high-risk, deep-strike, precision-guided missions.
With its 49kN thrust and sophisticated digital controls, the unmanned aerial vehicle functions as a subsonic platform without the need for an afterburner, in contrast to the initial afterburner-equipped model created for the Light Combat Aircraft (LCA), which had an 85kN thrust requirement. This basic distinction—the lack of an afterburner requirement—provides the stealth dimension that sets it apart from fighter aircraft engines, resulting in its classification as a “derivative engine or dry engine,” according to GTRE director SV Ramana Murthy.
With a 75 percent similarity to the original Kaveri engine, the UCAV project, which was approved in 2018, exhibits exceptional technical maturity. The platform aims for challenging operational criteria, such as two-hour endurance requirements, service ceilings of 13,000 meters, and Mach 0.9 speed capabilities.
The KDE configuration for the 13-ton Ghatak stealth UCAV is the focus of current development work; thrust output parameters range from 50 to 55 kN, with future improvements reaching 60 kN. Utilizing insights from collaborations with Russia’s NPO Saturn and France’s Safran, the engine integrates enhanced compressor and turbine designs, as well as sophisticated materials, to rectify previous development flaws.
With a maximum take-off weight of over 13 tonnes, service ceiling capabilities between 30,000 and 40,000 feet, an operational range of over 1,000 kilometers on internal fuel, and subsonic cruising speeds of roughly Mach 0.8, the Ghatak UCAV itself boasts outstanding specs.
When compared to foreign engine development initiatives, the Kaveri program’s total investment since its commencement in 1983 is a pitiful $239 million (about ₹2,000 crore at current exchange rates).
For comparison, it took $1.6 billion to develop the Eurojet EJ200 engine for the Eurofighter Typhoon between 1985 and 1995, and it cost $1.6 billion to test the Dassault Rafale’s Snecma M88 in 1989. While China has invested an astounding $42 billion in aviation engine development efforts, the Pratt & Whitney F135 for the F-35 Lightning II needs $6.7 billion in development costs.
GTRE is working on next-generation propulsion systems for sixth-generation fighter applications as a result of the KDE’s success, which has sparked ambitious future development initiatives.
For fifth-generation aircraft, the company is creating a 120kN thrust engine using technologies that represent many
improvements in thrust-to-weight ratios, turbine temperatures, and operational life requirements surpassing 2,000 hours that beyond fourth-generation capabilities. This growth path involves possible joint development agreements and advanced knowledge transfer with global engine manufacturers including Safran, Rolls-Royce, and General Electric.
The Advanced Medium Combat Aircraft (AMCA) MK-2 variant is the focus of the sixth-generation engine development program. Its specifications, which include a targeted Turbine Entry Temperature of 2100 Kelvin, place it in the exclusive group of the most cutting-edge power plants in the world. When compared to the WS-15 engine built for China’s J-20 stealth fighter, this high-temperature operation capability directly translates to higher engine performance, potentially enabling India to overtake decades of Chinese advancements in jet engine technology.
The building of GTRE’s 130kN Twin Engine Test Bed Facility at Rajankunte, Bangalore, which started in September 2023 and is anticipated to be fully operational by October 2025, is one example of supporting infrastructure development.
As India has reached a maturity level where international engine houses have evaluated and assessed Indian capabilities, acknowledging the country’s readiness to undertake higher engine capability design and development programs, K Rajalakshmi Menon, Director General of Aeronautical Systems at DRDO, highlights that successful collaboration requires equal partnership capabilities. This acknowledgement establishes India as a reliable collaborator in the development of cutting-edge aircraft technology, which is crucial for attaining the strategic autonomy that necessitates technological independence.
The Kaveri program’s transition from apparent failure to renewed significance serves as an example of the long-term benefits of consistent investment in R&D in vital technology areas.
The program shows that, although it takes time and effort, indigenous technological development eventually lays the groundwork for strategic autonomy and less reliance on foreign suppliers in vital defense capabilities, as the KDE variant gets closer to certification for the Ghatak stealth UCAV and derivative applications spread across naval and ground vehicle platforms.
