Chennai: The Indian Space Research Organisation (ISRO) has achieved a major milestone in the development of rocket systems for satellite launches. ISRO successfully hot tested the cryogenic upper stage for geosynchronous launch vehicle (GSLV) on 28th October for 50 seconds at the liquid propulsion systems centre (LPSC) test complex at Mahendragiri. The first of its kind test in India, the performance was as predicted.

ISRO has taken up indigenous development of cryogenic stage with regenerative cooled engine, which produces a thrust of 69.5 kN in vacuum, to replace the existing procured stage from Russia currently used in GSLV flights.

As part of this effort, the cryogenic engines have been realised and tested earlier for a cumulative duration of 6000 seconds.

In the stage level hot test all stage elements like engine, insulated propellant tanks, booster pumps, fill and drain systems, pressurisation systems, gas bottles, igniters, cold gas orientation and stabilisation system and others worked as per the actual flight standards in unison.

The stage uses the cryogenic propellants namely liquid hydrogen at -250º C and liquid oxygen at -196º C. The turbo pumps used for drawing the propellant from the tanks operate at the very high speed of 42,000 rpm.

The materials used to operate at cryogenic temperatures, chilling processes, interplay of various critical engine parameters and a host of other technical aspects make the development of cryogenic stage a very challenging task.

The Indian industries have significantly contributed in the realisation of the cryogenic stage. This hot test has demonstrated the design adequacy and performance of the integrated flight system, further tests for this flight unit are planned to validate robustness of the design. After completion of the qualification tests, the indigenous cryogenic stage is planned to be flight tested in GSLV- D3 mission next year.