Bangalore: As the GSLV MK-III or LVM3 prepares for its second commercial launch, expected in early 2023, ISRO’s efforts on enhancing its weight-lifting capacity is gaining pace with the space agency expected to complete qualification tests for the semi-cryogenic stage (SC120) in a couple of months.

GSLV MK-III is India’s heaviest rocket yet. Here’s some perspective: Between May 26, 1999 (India’s first commercial launch) and October 22, 2022, ISRO launched 345 foreign satellites, all on PSLV, which together weigh 9,326.4kg. On October 23, 2022, in its first commercial mission, the GSLV MK-III put into orbit 5,796kg in a single mission.

Of course, these missions are incomparable given that most of the foreign satellites launched by PSLV were ride-sharing payloads and include tens of small, micro and nano satellites. But there’s no doubt that the Mk3 clearly enhances India’s prospects. In fact, ISRO chairman S Somanath said last week: “The GSLV MK-III is India’s best commercial bet.”

At present, the GSLV MK-III can carry around four tons to a geostationary orbit (GTO) and at least six tonnes to a low earth orbit (LEO). Induction of the high propulsive SC120, along with increased propellant loading of the cryogenic upper stage (CUS) can enhance this to six tons (GTO) and 10 tonnes (LEO). ISRO spokesperson Sudheer Kumar told TOI: “The GSLV MK-III program was envisaged to eventually carry at least 10 tonnes to LEO and six tonnes to GTO orbits. We’ll achieve this with an upgrade of the cryo stage with additional propellant loading and induction of the semi-cryo stage that will replace the L110…”

“...Work on the semi-cryo engine is almost nearing completion. Qualification tests are in progress. Stage and engine development phase is complete and the test stand is getting ready for carrying out tests. At present sub-system level tests are going on at testing facilities in Mahendragiri and LPSC (Liquid propulsion systems centre),” he added. GSLV MK-III is a three-stage vehicle with two solid strap-on motors (S200), one liquid core stage (L110) and a high-thrust cryogenic upper stage (C25). While the S200 will remain the same, the SC120 will replace L110 and C25 will be upgraded. “...We are expecting qualification to be completed in a couple of months unless some anomalies are found which may call for repeated tests, which are not unusual during the evolution stage,” Kumar said.

He added that aside from increasing the payload carrying capability, the new configuration would also make the vehicle safer as it will use non-toxic elements compared to L110.

“It will use refined kerosene, which is like aviation fuel. This means stage handling will be very safe, there will be an increased capacity, ground systems handling becomes much simpler and storage leakages and human aspect concerns get reduced while handling the stage,” Kumar said. The GSLV MK-III project was first approved in 2002, with a mandate of achieving the capability to launch a four-tonne class satellite to Geosynchronous orbit (GEO), which ISRO achieved through three demonstration missions.