Can ISRO’s Rocket Engine Expertise Propel India Toward Indigenous Fighter Jet Engines?

India has long sought independence in the realm of defense technology, but one critical challenge persists: developing indigenous fighter jet engines that can rival those used in modern military aviation. Recently, Dr. S. Somanath, Chairman of the Indian Space Research Organisation (ISRO), spotlighted the disparity between India’s achievements in rocket engines and its ongoing reliance on foreign technology for fighter jets. His remarks have sparked a conversation on whether ISRO's prowess in rocket propulsion could be the answer to India’s quest for a homegrown fighter jet engine.

India’s Rocket Engine Success and the Fighter Jet Engine Gap

India’s strides in rocket technology have been nothing short of impressive. ISRO has developed a range of propulsion systems, including liquid-fueled Vikas engines and sophisticated cryogenic engines. These technologies have enabled ambitious missions like Mangalyaan (Mars Orbiter Mission), Chandrayaan (lunar missions), and the upcoming Gaganyaan human spaceflight program. ISRO’s cryogenic engine technology, particularly, is advanced enough to place it among a select few nations, such as the U.S., Russia, China, Japan, and the European Union, that possess mastery over these high-performance rocket systems.

In contrast, India’s defense sector has struggled to produce a viable indigenous fighter jet engine. The nation’s Light Combat Aircraft (LCA) Tejas currently relies on American-made engines, specifically the General Electric F404 for operational variants and the more powerful F414 engine planned for Tejas Mk2. While this reliance ensures that the Tejas is powered by a reliable, high-performance engine, it also ties India’s defense readiness to international supply chains, an arrangement that Dr. Somanath and others view as limiting for a country with India’s ambitions.

The Distinct Demands of Jet Engines and Rocket Engines

Though ISRO’s achievements in rocket engine technology are monumental, translating that expertise to the realm of fighter jet engines is a complex challenge. Rocket engines are designed to provide immense thrust for a short duration and typically operate in outer space, where the absence of atmospheric resistance allows them to function without the intricate cooling mechanisms needed for sustained use in Earth’s atmosphere. On the other hand, fighter jet engines must withstand prolonged periods of operation under extreme conditions: they need to deliver stable, reliable thrust at supersonic speeds, handle rapid changes in power, and be lightweight enough to not compromise aircraft maneuverability.

Jet engines face additional engineering challenges like dealing with extremely high temperatures (often above 1,500°C in the turbine section), requiring advanced cooling techniques and materials capable of withstanding sustained thermal stress. Metals such as single-crystal nickel alloys are frequently used, and precise design tolerances are necessary to prevent performance losses at high speeds. Additionally, fighter jets require high-pressure compression systems and robust afterburners to deliver the thrust needed for rapid acceleration and combat maneuvers. The development of such advanced propulsion systems requires experience that India’s defense sector has yet to achieve independently.

Can ISRO’s Knowledge Support India’s Fighter Jet Engine Program?

While rocket and jet engines are fundamentally different, ISRO’s depth of experience in propulsion technologies could offer valuable insights to bridge this gap. Dr. Somanath's suggestion raises the possibility of knowledge transfer, where ISRO's expertise in advanced combustion, materials science, and thermal management could provide a boost to the country's defense efforts. ISRO has developed engines that operate in vacuum-like conditions and require extreme temperature and pressure management. The agency has also pioneered systems to efficiently monitor and control complex propulsion mechanisms, all of which are essential skills for jet engine development.

For instance, ISRO’s cryogenic engines, which use liquid hydrogen and liquid oxygen, have paved the way for innovations in fuel handling and combustion stability—qualities essential to modern aircraft engines. Cryogenic engines, while not identical to jet engines, involve many shared engineering principles, such as advanced fluid dynamics, thermal shielding, and material endurance under thermal cycles. ISRO’s development of the Next-Generation Launch Vehicle (NGLV), intended for heavy-lift and human-rated missions, will involve even more sophisticated propulsion technologies. This expertise might be adapted to address specific challenges in jet engines, from improving material resilience to refining combustion and thermal management techniques.

The Potential Path Forward: Collaboration and Cross-Disciplinary Innovation

Though not a direct proposal, Dr. Somanath’s remarks hint at a new strategy that could harness the best of India’s scientific capabilities to close this technology gap. Collaboration between ISRO and India’s Defense Research and Development Organisation (DRDO) could lead to a pooling of expertise, where ISRO’s strengths in propulsion and DRDO’s understanding of aviation technology converge. Such partnerships would likely focus on developing core technologies for jet engines, particularly in areas like high-temperature materials, cooling systems, and high-efficiency combustors.

A major opportunity lies in developing advanced materials that can withstand both high temperatures and mechanical stresses, key for aircraft engines. DRDO has some experience in this area, having experimented with the Kaveri engine project, although it ultimately fell short of operational readiness. By integrating ISRO’s insights in materials engineering with DRDO’s knowledge of aircraft dynamics, India may find a path toward a reliable indigenous jet engine. Additionally, private sector participation could accelerate this process by bringing in advanced manufacturing techniques and innovations in material science, especially with recent government efforts to encourage defense startups.

Conclusion: Realistic Expectations and Long-Term Vision

While ISRO’s experience offers valuable expertise, developing a fighter jet engine remains a long-term goal requiring concerted effort across multiple fields. ISRO’s knowledge can accelerate key aspects of research, but a sustainable jet engine development program would require significant government funding, policy support, and a skilled workforce dedicated to this mission. With collaboration, both in-house and international, and a vision that prioritizes indigenous capabilities, India may well see success in this endeavor over the coming decades.