The liquid engines being flown in the fourth stage of PSLV (PS4) use nozzle divergent made up of imported Columbium (C103) material.

An alternate material, Stellite (KC20WN), was proposed for the nozzle divergent realization to achieve Atmanirbharta along with associated cost savings. Stellite is a cobalt based alloy with additions of Chromium, Nickel, Tungsten and Iron.

It is a material which retains good strength at high temperatures up to 11500C and hence becomes a suitable material for high temperature applications. As part of the qualification programme, 3 hot tests were already completed on two hardware in the first phase.

On April 08, 2025, the final test of the qualification program was successfully completed through a hot test for a long duration of 665 seconds at the test facility in ISRO Propulsion Complex, Mahendragiri. The use of this alloy has resulted in cost savings to the extent of 90%.

Human Rated VIKAS Engine For L110 Stage Qualification

Earlier, The final long duration hot test of human rated L110-G Vikas Engine is successfully accomplished for the planned qualification duration of 240 s on April 6, 2023 at ISRO Propulsion Complex (IPRC), Mahendragiri. The successful completion of this test marks a major milestone in the human space flight programme, Gaganyaan, of ISRO. The air-lit liquid core stage of human-rated launch vehicle (LVM3-G) uses two L110-G Vikas engines in clustered configuration. With this test all the planned qualification tests of the engine are completed successfully.

Design and realization of L110 stage for Gaganyaan is carried out at Liquid Propulsion Systems Centre (LPSC), assembly and integration and testing is carried out at IPRC. Engine Gimbal Control system was developed by VSSC.

The Vikas engine uses storable propellants in a pump-fed gas generator cycle. Human rated Vikas engine has higher structural margins for sub-systems, improved assembly process and additional measurements for health monitoring.

Human rated Vikas Engine development hot tests were conducted in a step-by-step manner at Principal Test Stand, IPRC. Nine engines had undergone 14 hot tests with a cumulative duration of 1215 s, including four long duration tests of 240 s each. Drawn from the extensive legacy and experience of liquid rocket engine development, the test campaign envelopes extreme operating durations, off-nominal mixture ratios and thrust level conditions as compared to flight operating conditions. Four sets of hardware used for this test programme were fabricated at various Indian industries.

Electro-mechanical Gimbal actuators and Command System module for engine pilot pressure control, with multiple redundancies were also qualified in the test. ISRO could complete the human rated L110-G Vikas engine qualification within a short span of three years.

The test was witnessed by former ISRO Chief S Somanath, Chairman ISRO/ Secretary DoS Dr. V Narayanan, Director, LPSC, Dr. S Unnikrishnan Nair, Director, VSSC, J Asir Packiaraj, Director, IPRC and other functionaries.

ISRO News