The nozzle divergence used in the PSLV fourth stage (PS4) liquid engines is composed of imported Columbium (C103) materialFor the nozzle divergence realization to accomplish Atmanirbharta and related cost reductions, Stellite (KC20WN) was suggested as a substitute material. Stellite is an alloy based on cobalt that also contains iron, tungsten, nickel, and chromium.
It is a material that is appropriate for high temperature applications because it maintains acceptable strength at temperatures up to 11,500C. Three hot tests on two pieces of hardware were already finished in the first phase of the certification procedure.
.The qualifying program’s last test was successfully finished on April 8, 2025, at the ISRO Propulsion Complex in Mahendragiri, using a hot test that lasted 665 seconds. Costs have been reduced by 90% as a result of using this alloy.
VIKAS Engine with Human Rating for L110 Stage Qualification
Prior to this, on April 6, 2023, the ISRO Propulsion Complex (IPRC), Mahendragiri, successfully completed the last long-duration hot test of the human-rated L110-G Vikas Engine for the scheduled qualifying period of 240 seconds. This test’s successful conclusion is a significant turning point in ISRO’s Gaganyaan manned space travel program. Two clustered L110-G Vikas engines power the human-rated launch vehicle’s (LVM3-G) air-lit liquid core stage. All of the engine’s scheduled qualifying tests have been successfully finished with this test.
The Liquid Propulsion Systems Centre (LPSC) is responsible for the design and implementation of the L110 stage for Gaganyaan, while IPRC handles the assembly, integration, and testing. VSSC was responsible for developing the Engine Gimbal Control system.
The Vikas engine is a pump-fed gas generator cycle that employs storable propellants. Higher structural margins for subsystems, an enhanced assembly procedure, and extra health monitoring data are all features of the human-rated Vikas engine.
At the Principal Test Stand, IPRC, human-rated Vikas Engine development hot tests were carried out in a methodical fashion. Nine engines were put through 14 heat tests totaling 1215 seconds, including four long-duration tests of 240 seconds each. The test program encompasses severe running durations, off-nominal mixture ratios, and thrust level situations in comparison to flight operating conditions, drawing on the vast history and knowledge of liquid rocket engine development. For this test program, four sets of hardware were manufactured at different Indian factories.
The test also certified the Command System module for engine pilot pressure control with multiple redundancies and electro-mechanical gimbal actuators. In about three years, ISRO might finish the human-rated L110-G Vikas engine certification.
J Asir Packiaraj, Director, IPRC; Dr. S Unnikrishnan Nair, Director, VSSC; Dr. V Narayanan, Chairman ISRO/Secretary DoS; former ISRO Chief S Somanath; and other officials saw the test.
