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The Indian Space Research Organisation (ISRO) is taking a significant step forward in its Reusable Launch Vehicle (RLV) technology development program. As reported by The Times of India (TOI), ISRO plans to utilize a modified Geosynchronous Satellite Launch Vehicle (GSLV) rocket to launch RLVs for orbital re-entry demonstration missions in the next phase of testing.

The key modification to the GSLV involves replacing its powerful cryogenic upper stage with a modified version of the PS4 stage, the last stage of the PSLV rocket. This switch is driven by the weight of the RLVs being tested. With an expected weight of 3.5 to 4 tons, the RLVs don’t require the massive energy output of the GSLV’s cryogenic stage.

The PSLV is a reliable and well-established expendable launch vehicle designed and operated by ISRO. It played a crucial role in enabling India to launch its IRS satellites into Sun-synchronous orbits, previously reliant on commercial services from Russia. Additionally, the PSLV is capable of launching small satellites into Geostationary Transfer Orbit (GTO).

ISRO anticipates the need for multiple orbital re-entry tests. To facilitate this, the RLVs used in these missions will be six times larger than the RLV Technology Demonstrator (RLV-TD) that ISRO has been employing for initial testing purposes.

S Unnikrishnan Nair, director of the Vikram Sarabhai Space Centre (VSSC), which leads the RLV program, provided insights into the decision behind the GSLV modification. He explained to TOI, “While the overall size of the RLV will increase, the mass won’t go up by a factor of six. Given the vehicle’s weight, the PS4’s propulsion is sufficient, eliminating the need for the GSLV’s cryogenic stage.”

The scaled-up RLV will incorporate improved thermal protection systems, critical for safeguarding the vehicle from extreme heat during re-entry into the Earth’s atmosphere.

Nair emphasized the critical aspects of takeoff, landing, and re-entry for the RLV. “The takeoff will be vertical, assisted by the rocket. Landing, however, requires a smooth descent. We need to develop various systems to manage re-entry, runway approach, precise touchdown, centerline alignment, parachute deployment, and the entire software to orchestrate these maneuvers,” he said.

The re-entry process necessitates positioning the RLV with its belly facing the incoming atmosphere to generate drag and decrease speed, effectively managing the energy involved in transitioning from orbit to landing.