Moon rock: Chandrayaan-4 a test for Isro's ambitious manned moon mission

The Indian Space Research Organisation (Isro) has an ambitious plan for the Chandrayaan-4 mission, targeted for 2027. The mission, cleared recently by the Cabinet with a tentative budget of Rs 2,104 crore, aims to return lunar samples safely to Earth for study.

It will feature five modules launched on two geosynchronous launch vehicle mark 3 (LVM3) rockets, which will be assembled in space into one composite vehicle. The mission includes a lander, which will detach to collect a few kg of soil and rock samples from the lunar surface and return to Earth while carrying out other scientific experiments.

The propulsion module will ferry the combined modular spacecraft. The lander module will land on the moon with the instrumentation. The ascender module will detach from the lander and launch from the moon with the samples to enter a lunar orbit. The transfer module will collect the samples from the ascender module and transfer them to the re-entry module and that will loop back around Earth while releasing the payload to fall safely to Earth for collection.

The key tasks include space assembly, soft landing, collecting surface and sub-surface samples, and returning them to Earth safely while preventing contamination.

Very complex docking manoeuvres will be critical for success both for the assembly as well as the detachment of modules. While Chandrayaan-3 demonstrated Isro had the capability to manage a controlled soft landing, this is much more ambitious across various stages, including space assembly as well as re-entry to the Earth atmosphere with a delicate payload. Roving on the surface, the hopping of the lander module, and returning the propulsion module to the Earth orbit are involved. 

This would demonstrate a grasp of several of the technologies required for a manned moon mission, which is on Isro’s long-term “to do” list. However, of course, there is a vast difference between ferrying a few kg of rocks and transporting human beings so this is only the first step on the journey of putting Gaganauts on the moon.

After touchdown, a robotic arm, the surface sampling robot will scoop 2-3 kg samples around the landing site and transfer them to the ascender module. Meanwhile, a drilling mechanism will collect sub-surface samples and transfer these. The containers with samples will be sealed to prevent contamination and leakage. After collection is completed, the ascender module would ascend and dock with the transfer-and-re-entry module. 

Samples will be transferred from the ascending module to the re-entry module. The transfer-and-re-entry module will return to Earth. At a suitable point, the re-entry module would be separated from the transfer module and re-enter Earth’s atmosphere and finally land. It is designed to land on solid ground.

Major new technologies are required for docking/undocking, landing, safe return to Earth and sample collection and analysis. The mission is scheduled to be completed within 36 months with industry and academia involved in design, manufacture and scientific research.

Isro’s ambitions have grown along with its successes. Alongside Chandrayaan-4, the Cabinet also cleared a Venus orbital mission, which will be even more challenging.

While the Mangalayaan missions have demonstrated Isro can design and operate a planetary orbiter, Mars has a thin clear atmosphere. Venus has a very thick, corrosive atmosphere and far higher gravity, presenting more daunting challenges.

However, each one of Isro’s missions, even the failures, has gathered valuable data and helped improve technological capability. Those have translated into a series of useful terrestrial applications, and gradually brought Isro closer to being a big player in the satellite market while building India's aerospace and space ecosystems.