ISRO has achieved a significant milestone through the successful test of indigenously developed Cryogenic Stage, to be employed as the upper stage of India's Geosynchronous Satellite Launch Vehicle (GSLV). The test was conducted for its full flight duration of 720 seconds today (November 15, 2007) at Liquid Propulsion test facility at Mahendragiri, in Tamil Nadu. With this test, the indigenous Cryogenic Upper Stage has been fully qualified on the ground. The flight stage is getting ready for use in the next mission of GSLV (GSLV-D3) in 2008.

It may be recalled that a ground test for 480 seconds of the complete stage was conducted on August 4, 2007.

The indigenous Cryogenic Upper Stage (CUS) is powered by a regeneratively cooled cryogenic engine, which works on staged combustion cycle developing a thrust of 69.5 kN in vacuum. The other stage systems include insulated propellant tanks, booster pumps, inter-stage structures, fill and drain systems, pressurisation systems, gas bottles, command block, igniters, pyro valves and cold gas orientation and stabilisation system. Liquid Oxygen (LOX) and Liquid Hydrogen (LH2) from the respective tanks are fed by individual booster pumps to the main turbo-pump, which rotates at 39,000 rpm to ensure a high flow rate of 16.5 kg/sec of propellants into the combustion chamber. The main turbine is driven by the hot gas produced in a pre-burner. Thrust control and mixture ratio control are achieved by two independent regulators. LOX and Gaseous Hydrogen (GH2) are ignited by pyrogen type igniters in the pre-burner as well as in the main and steering engines.

Apart from the complexities in the fabrication of stage tanks, structures, engine and its sub-systems and control components, CUS employs special materials like Aluminum, Titanium, Nickel and their alloys, bi-metallic materials and polyimides. Stringent quality control and elaborate safety measures have to be ensured during assembly and integration.

Liquid Propulsion Systems Centre (LPSC) is the lead centre for the development of Cryogenic Upper Stage with the involvement of Vikram Sarabhai Space Centre (VSSC) and other ISRO centres as well as several industries, both in public and private sector.

The successful ground test of the indigenous Cryogenic Upper Stage for the full flight duration has validated the design robustness and performance adequacy for its use in GSLV.