MAHENDRAGIRI, October 6 — The Indian Space Research Organisation (ISRO) achieved a critical technological milestone on Tuesday toward executing the landmark Chandrayaan-4 lunar sample return mission, successfully completing a 750-second qualification hot test of the lander descent module's throttleable bipropellant engines at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu.
The ground-firing simulated dynamic terminal descent manoeuvres, rigorously validating the rapid variable-thrust response demanded by autonomous Hazard Detection and Avoidance (HDA) algorithms during soft-touchdown phases over rugged lunar topography. Space scientists confirmed that continuous telemetry demonstrated stable combustion pressures, flawless propellant valve actuations, and precise throttling between 20 percent and 100 percent rated thrust levels without thermo-acoustic instabilities.
Unlike previous lunar landings, Chandrayaan-4 incorporates a complex multi-stage architecture consisting of five integrated modules—Propulsion, Descender, Ascender, Transfer, and Re-entry Modules—launched across two separate LVM3 missions with autonomous docking in lunar and Earth orbits. The mission objective entails drilling up to two metres beneath the lunar surface, extracting regolith core samples, transferring them into an ascent vehicle, and returning the sealed payload safely through Earth's atmosphere.
India's space exploration milestones, autonomous docking architectures, cryogenic propulsion, and interplanetary mission profiles are central components of the UPSC Civil Services Preliminary and Main (GS-III: Science & Technology) syllabi. Aspirants should note that August 23 is officially designated as 'National Space Day' to commemorate the historic landing of Chandrayaan-3 near the lunar South Pole in 2023, while the Union Cabinet accorded formal financial sanction of ₹2,104 crore for Chandrayaan-4 in September 2024.