ISRO's upcoming Chandrayaan-4 mission, representing India’s inaugural attempt to retrieve lunar samples, is facing significant timeline uncertainties following a strategic decision to switch to an upgraded launch vehicle.

The mission will now utilise an enhanced version of the LVM-3 rocket, which incorporates the sophisticated SE2000 semi-cryogenic engine. While this transition is designed to significantly increase payload capacity, it introduces a potential conflict with the mission's ambitious October 2027 launch target, as current estimates suggest the engine might not be fully operational until the 2028–29 window.

Recent parliamentary reports have highlighted various challenges associated with this redesign, including delays in the procurement of raw materials and underspending of the allocated budget.

These fiscal and logistical shifts underscore the immense technical complexity and high stakes of the mission. Chandrayaan-4 is uniquely demanding, as it aims to collect and return up to three kilograms of soil from the Moon’s south pole—a region that has never before been sampled by any nation.

To manage the massive 9,200 kg payload, which exceeds the lift capacity of a standard single rocket, ISRO has devised a plan involving two separate LVM-3 launches. These launches will carry five distinct modules that are designed to dock in Earth orbit before proceeding toward the Moon.

The switch to the SC LVM-3 variant, powered by the SE2000 engine, is intended to boost the payload capacity to geostationary transfer orbit from approximately 4,200 kg to 5,200 kg, ensuring each half of the mission reaches the precise orbit required for successful docking.

Development of the SE2000 engine, which delivers a powerful 2,000 kN of thrust, is intended to replace the 1,600 kN liquid-fuel engine currently used in the L110 core stage. Progress has been made between 2025 and early 2026, with ISRO completing several short-duration power head tests.

These milestones include a successful modified-subsystem test in January 2026 and the qualification of the Isrosene propellant tank. Beyond this mission, the engine is also being developed for future reusable LVM-3 variants, which could lower costs by allowing the recovery of the first stage.

Despite these technical successes, the timeline remains a primary concern. A fully integrated hot test of the SE2000 is scheduled for late 2026, but the readiness of the SC LVM-3 may still lag until 2028 or 2029.

This creates a gap between the hardware availability and the 2027 mission goal. If ISRO can successfully accelerate its integration and testing phases, the mission may proceed on schedule, marking a massive leap in propulsion technology.

However, further delays could push the mission into the next decade, potentially synchronising it with reusable rocket technology and fundamentally shifting India’s competitive standing in the global lunar race.

Agencies