The GSLV-F10/EOS-03 mission, which lifted off from Sriharikota on August 12 last year failed due to ‘deviation in the performance’ of the cryogenic upper stage (CUS) of the launch vehicle, a national-level Failure Analysis Committee (FAC) constituted in the aftermath has found.
Although the Geosynchronous Satellite Launch Vehicle (GSLV) had a normal lift-off after a 26-hour countdown, the mission had to be aborted much to the dismay of the Indian Space Research Organisation (ISRO). The FAC, which consisted of experts from the space agency and the academia, submitted its findings on Thursday.
The FAC has concluded that a leak in a Vent and Relief Valve (VRV), probably triggered by damage in the soft seal, resulted in lower pressure in the LH2 (Liquid Hydrogen, the propellant) tank when the CUS engine ignited. This caused the Fuel Booster Turbo Pump (FBTP) to malfunction, ultimately leading to the failure of the mission.
After lift-off, the build-up of pressure in the LH2 tank was ''not normal,'' leading to the lower tank pressure, ISRO said on Friday. This caused the FBTP, mounted inside the LH2 tank which feeds the main turbopump of the engine, to malfunction, resulting in insufficient propellant flow into the engine thrust chamber.
Validation
''Detailed studies indicate that the most likely reason for the observed reduction in LH2 tank pressure is a leak in the respective VRV, which is used for relieving the excess tank pressure during flight. Computer simulations as well as multiple confirmatory ground tests, closely simulating the conditions in the GSLV-F10 flight, validated the analysis by the FAC,'' ISRO said.
The glitch in CUS performance was observed at 297.3 sec into the flight and the onboard computer aborted the mission at 307 seconds into the flight.
The ''most probable'' reason for the leakage of VRV valve, according to ISRO, is damage in the soft seal. And this may have occurred during valve operations or was caused by contamination and valve mounting stresses induced by cryogenic temperature conditions.
Recommendations
According to ISRO, the FAC has made comprehensive recommendations for ''enhancing the robustness'' of the CUS for future GSLV missions. Recommendations include the incorporation of an active LH2 tank pressurisation system for guaranteeing sufficient pressure in the tank before the engine burns. Other recommendations include strengthening the VRV and associated fluid circuits to avoid leakage.
The GSLV Mission had aboard it the EOS-03, an earth observation satellite which was to be placed in a Geosynchronous Transfer Orbit (GTO). It marked the eighth flight with an indigenously-built cryogenic engine and the 14th flight of the GSLV. Initial investigations conducted immediately after the failed launch had pointed to an anomaly in the CUS as the villain.
