ISRO’s Stellite Nozzle Divergent

Recently, the Indian Space Research Organisation (ISRO) tested a new Indian-made material for the nozzle divergent of the PSLV’s fourth stage (PS4). The new material is Stellite (KC20WN) – a cobalt-based alloy developed in India. This innovation marks step towards self-reliance in India’s space programme. Final hot test was done on April 8, 2025, at ISRO Propulsion Complex, Mahendragiri. The test lasted 665 seconds. In total, 3 hot tests were completed on 2 hardware units as part of the qualification.

What is a Nozzle Divergent?

• A nozzle divergent is the wider part of a rocket nozzle that helps increase the speed and efficiency of gas flow, giving more thrust.
• It is part of a Convergent-Divergent (CD) nozzle:
  • Convergent: Narrows to increase speed and reduce pressure.
  • Throat: The narrowest point where gas reaches sonic speed (Mach 1).
  • Divergent: Expands to push gas to supersonic speed, giving more thrust.

Stellite Nozzle Divergent

ISRO proposed Stellite (KC20WN) as a cost-effective alternative. Stellite can withstand temperatures up to 1150°C, making it ideal for high-temperature applications. This switch results in a 90% reduction in costs associated with imported materials.

Qualification Testing

ISRO conducted a rigorous qualification programme. Three hot tests were completed prior to the final test. On April 8, 2025, a long-duration hot test lasting 665 seconds was successfully executed. This test confirmed the performance and reliability of the Stellite nozzle in real-world conditions.

Month: Current Affairs - April, 2025

Category: Science & Technology Current Affairs