Chandrayaan-3 To Land On Lunar Surface Tonight. Know Why It Took The Spacecraft 40 Days To Reach The Moon

While NASA's Apollo-11 reached the Moon in four days, China's Chang'e 5 reached lunar orbit in five days, and Russia's Luna 25 in seven days, Chandrayaan-3 took 22 days to enter lunar orbit.

Chandrayaan-3, which launched on July 14, 2023, is scheduled to land on the lunar south pole on August 23, 2023, over 40 days after launch. While NASA's Apollo-11 reached the Moon in four days, China's Chang'e 5 reached lunar orbit in five days, and Russia's Luna 25 in seven days, Chandrayaan-3 took 22 days to enter lunar orbit. Chandrayaan-3's landing module came close to the Moon on August 20. A question arises about why the Indian Space Research Organisation's (ISRO's) third lunar exploration mission took so long to reach the Moon, while other spacecraft reached Earth's natural satellite in just a few days. The reasons behind this are many, including launch vehicle limitations and the amount of fuel used. 

Though Luna 25 crashed on the Moon on August 20, a day ahead of its scheduled landing date, the spacecraft safely managed to reach lunar orbit within a few days after launch. In order to understand why Chandrayaan-3 took a relatively longer time to come close to the Moon than other lunar exploration missions, ABP Live spoke to Manish Purohit, a former ISRO scientist, who was involved in the Mangalyaan and Chandrayaan-2 missions; and Debadatta Mishra, a former ISRO scientist, and co-founder of Erisha Space, a New Delhi-based space-tech firm. 

Why Chandrayaan-3 took 40 days to reach the Moon

ISRO's Launch Vehicle Mark III (LVM3), which was used to launch Chandrayaan-3, has certain limitations in terms of propelling the lander module directly into lunar transfer orbit. Due to this challenge, ISRO decided to leverage principles of physics and harness gravity to perform Earth-bound manoeuvres.

“The trajectory and timeframe of a space mission are profoundly influenced by the propulsion capacity of the launch vehicle employed. In the case of Chandrayaan-3, the utilisation of ISRO's LVM3 launch vehicle comes with certain limitations in propelling the module directly into the Lunar Transfer Orbit. This intriguing challenge led ISRO to ingeniously harness the fundamental principles of physics, orchestrating a series of precisely calculated manoeuvres around Earth to harness the gravitational forces to its advantage,” Purohit explained. 

The Chandrayaan-3 spacecraft performed five strategic manoeuvres around Earth, which led to it being injected into lunar orbit on August 5. Similarly, Moon-bound manoeuvres were performed to refine the trajectory of Chandrayaan-3, and lower the lunar orbit. 

Luna 25 was launched atop a Soyuz-2 Fregat launch vehicle, which is quite powerful, and injected Luna 25 into lunar orbit within five days.

“This rapid acceleration shortens the time frame considerably,” said Purohit.

Another reason why Chandrayaan-3 took so long to reach the Moon is that the mission used a relatively small amount of fuel, and chose a slower and gradual trajectory for lunar insertion, said Mishra. “ISRO has managed to use very less fuel by employing a trajectory that utilises the gravitational effects of both earth and moon.”

On August 20, ISRO wrote on X (formally Twitter) that the Chandrayaan-3 mission is on schedule, the systems are undergoing regular checks, and that smooth sailing is continuing. ISRO also shared images of the Moon captured by the Lander Position Detection Camera (LPDC) on August 19, from an altitude of about 70 kilometres, and pictures captured by the Lander Imager Camera 4 on August 20. 

If Chandrayaan-3 successfully lands on the lunar south pole, India will become the first country to achieve this feat.