ISRO simulation of India's indigenous Cryogenic stage during an orbit insertion manoeuvre 

It is expected to be launched in the second half of this year

The Geosynchronous Satellite Launch Vehicle (GSLV) with improvements added to its cryogenic upper stage (CUS) is expected to be ready in the second half of this year.

A high-level panel which examined last year's failed GSLV-F10/EOS-03 mission had recommended measures for making the CUS more robust. Indian Space Research Organisation's Liquid Propulsion Systems Centre (LPSC) is tasked with making the required modifications to the cryogenic engine-powered upper stage of the GSLV MK-II rocket.

A senior official of the Vikram Sarabhai Space Centre (VSSC), ISRO's lead unit on launch vehicles, says the next GSLV flight will be held once the modifications are incorporated.

The GSLV-F10 mission on August 12, 2021 was designed to place the earth observation satellite EOS-03 in a geosynchronous transfer orbit, but the upper stage of the rocket malfunctioned, forcing the space agency to abort the mission. A national-level Failure Analysis Committee (FAC) later concluded that a leak in a Vent and Relief Valve (VRV) had led to a lower build-up of pressure in the Liquid Hydrogen (LH2) propellant tank, leading to a failed mission.

Modifications planned include a mechanism to ensure sufficient pressure in the tank before the engine burns and strengthening of the VRV to avoid leaks.

On Thursday, Union Minister of State (Independent Charge) Science & Technology Jitendra Singh informed the Rajya Sabha in a written reply that computer simulations as well as multiple ground tests, ''closely simulating the conditions in the GSLV-F10 flight, had validated the analysis of the FAC.'' He points out that the satellite for the next GSLV mission is expected to be ready for launch in the fourth quarter of 2022 and the mission failure is not likely to delay ''related projects.''

The FAC, whose report was published in March, points to a leak in the VRV as the underlying reason for the failure. Pressure build-up in the liquid hydrogen (LH2) propellant tank was low when the upper stage engine was to ignite. This caused the fuel booster turbo pump inside the LH2 tank, which feeds the main turbopump of the engine to malfunction, affecting the flow of propellant into the engine thrust chamber.

Although the mission had a normal lift-off from Sriharikota, problems were noted at 297.3 second into the flight. At 307 seconds, the onboard computer aborted the mission.