On July 14, at 2:35 p.m. IST, the Indian Space Research Organisation (ISRO) is scheduled to initiate its third lunar mission, known as Chandrayaan-3. This will occur at the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh. Chandrayaan-3 holds great importance for India’s space program as it aims to expand our understanding of the Moon and its past. This mission will further facilitate the development of advanced technologies for upcoming lunar expeditions.
Assuming everything goes as planned, the 43.5-meter LVM-3 launch rocket will be responsible for propelling the spacecraft into an elliptical orbit around the Earth before embarking on its journey towards the Moon. The anticipated landing near the lunar south pole is projected to take place around August 23.
Image source: ISRO
The LVM-3 is a highly capable heavy-lift launch vehicle known for its capacity to transport a significant payload into space. It holds the distinction of being the most powerful rocket ever developed by ISRO, unmatched in its class.
Referred to as the ‘Bahubali’ of rockets, the LVM-3 consists of three stages and incorporates two solid-fuel boosters along with a liquid-fuel core stage. The solid-fuel boosters initiate the initial thrust, while the liquid-fuel core stage maintains sustained thrust to propel the rocket into orbit.
The mission entails deploying a 2-meter tall lander, which is designed to release a rover in the vicinity of the lunar south pole. The rover is anticipated to operate for approximately two weeks, conducting a series of experiments.
The primary objective of the Chandrayaan-3 mission is to accomplish what its predecessor could not—achieve a gentle landing on the lunar surface and conduct exploration using a rover.
If a successful soft landing is achieved, India will join the ranks of the United States, Russia, and China as the fourth country to accomplish this remarkable feat. This distinction has been vacant since the crash-landings of the missions from Israel and India in 2019, as well as the failures of the spacecraft carrying a lander rover from Japan and a rover from the UAE in 2022.
Although the mission objectives remain unchanged, scientists at the Indian Space Research Organisation (ISRO) have incorporated valuable lessons learned from the previous mission.
The design of the lander has been enhanced through a series of tests to ensure its performance under various circumstances, such as potential inability to reach the intended landing spot, failure of electronics or sensors, or velocity exceeding the required threshold, among other factors.
“Failure-based” design of Chandrayaan-3 and the failings of Chandrayaan 2
ISRO Chairperson S Somanath recently stated that the modifications made to the current Chandrayaan-3 mission were based on learning from past failures. He explained that instead of designing based on success, the approach for Chandrayaan-3 was focused on addressing potential failures and finding solutions for them.
During the Chandrayaan-2 mission, the lander and rover crash-landed on the Moon instead of achieving a soft landing. Somanath identified the main issue as the lander’s engines producing slightly higher thrust than anticipated.
During the descent, the lander had to maintain stability while taking pictures to determine the landing site. Errors accumulated, and when course corrections were initiated, the spacecraft’s ability to turn quickly was limited by its software. There were conflicting requirements for reducing vertical velocity while accelerating horizontally to reach the correct landing site. Consequently, when the lander did touch down, it had a higher-than-desired velocity.
Based on these lessons, several changes have been implemented in the current mission. First, the landing area has been expanded from a specific 500m x 500m patch targeted in Chandrayaan-2 to a safer 4km x 2.4km region where the lander can touch down. Second, the lander has been equipped with more fuel, enabling it to travel longer distances to reach the designated landing site or an alternate site if necessary.
Another significant change is that the lander will no longer rely solely on images taken during descent to determine the landing site. Instead, high-resolution images captured by the Chandrayaan-2 orbiter have been incorporated into the lander’s systems, and the lander will take additional images to confirm its precise location.
Furthermore, modifications have been made to the lander’s physical structure. The number of thrusters has been reduced from five to four, and the legs have been reinforced to withstand higher velocities during landing. Additional solar panels have been added to enhance power generation for the lander.
These adjustments have been made to address the issues faced during Chandrayaan-2 and increase the chances of a successful soft landing in the current mission, Chandrayaan-3.
