ISRO unveils lightweight carbon-carbon nozzle to boost rocket payload capacity

The Indian Space Research Organisation (ISRO) has introduced a lightweight Carbon-Carbon (C-C) nozzle for rocket engines, designed to improve several performance metrics of rocket engines such as thrust levels, specific impulse, and thrust-to-weight ratios, ultimately enhancing the payload capacity of launch vehicles.

The innovation was developed by ISRO's Vikram Sarabhai Space Centre (VSSC), which utilized Carbon-Carbon (C-C) Composites to fabricate a nozzle divergent boasting low density, high specific strength, and robust stiffness. The processes employed included the carbonization of green composites, Chemical Vapor Infiltration, and High-Temperature Treatment, ensuring that the nozzle maintains its mechanical properties even under high temperatures.

A significant aspect of the C-C nozzle is its protective anti-oxidation Silicon Carbide coating, which mitigates thermally induced stresses and boosts corrosion resistance, thereby allowing for extended operational temperature limits in challenging environments.

This advancement is poised to greatly benefit ISRO's flagship Polar Satellite Launch Vehicle (PSLV). Currently, the PSLV's fourth stage (PS4) uses twin engines with Columbium alloy nozzles. Replacing these with C-C composite nozzles could reduce the mass by about 67%, potentially increasing the payload capacity by 15 kg.

The efficacy of the new C-C nozzle divergent was confirmed during a 60-second hot test on March 19, 2024, at the ISRO Propulsion Complex (IPRC) in Mahendragiri, followed by a 200-second test on April 2, 2024, which achieved temperatures of 1216K, aligning with prior estimates.

The development involved collaboration between the Liquid Propulsion Systems Centre (LPSC) at Valiamala, which designed the test setup, and the IPRC at Mahendragiri, responsible for conducting the tests.