Chandrayaan-3's Moonshot: Why Soft Landing On Lunar Surface Is A Challenge

Chandrayaan-3 will today attempt a soft landing on the moon's south pole, a mission that could advance India's space ambitions and also expand knowledge of lunar water ice, potentially one of the most valuable resources on the moon.

While the mission has so far gone accordingly to plan, the final stage is being described as twenty minutes of terror that could be like the tight finish of a T20 match. The Chandrayaan-3 lander module, comprising of lander Vikram and rover Pragyaan, will have to mix precision and creativity to successfully navigate all the challenges associated with soft landing on the moon.

What is a soft landing?

A soft landing refers to the controlled descent and subsequent touchdown of a spacecraft on the lunar surface without causing significant damage to either the craft or its scientific instruments. It is achieved by reducing the spacecraft's speed gradually, allowing it to touch down gently. Such landings ensure a gentle interaction with the Moon's rugged terrain, enabling the collection of valuable data, exploration, and potentially serving as a precursor to human missions.

A hard landing, on the other hand, involves a greater impact between the spacecraft and the moon's surface.

What are the challenges with a soft landing?

To achieve a soft landing, the Chandrayaan-3 will have to conquer blazing speeds and then execute a precise controlled descent.

In a powered descent, the Vikram lander will start hurtling towards the moon surface at a velocity of 1.68 km per second which is nearly 6048 km per hour -which is almost ten times the velocity of an airplane.

Vikram lander will then slow down with all its engines firing - but the lander is still almost horizontal to the surface of the moon - this is called the rough braking phase which lasts for about 11 minutes.

Through some maneuvers, the Vikram lander will be made vertical to the moon surface, with this begins the 'fine braking phase'.

Even a tiny mistake in how the spaceship descends can cause it to crash or get damaged. It was in the fine braking phase, when the Vikram lander during the Chandrayaan-2 launch went out of control and tumbled to a crash.

The Chandrayaan-3 lander will face another adversary today in the form of lunar dust, minute abrasive particles which could create an exhaust plume around the craft.

What makes the South Pole tricky?

Attempted landings on the moon have failed before. Russia's Luna-25 craft had been scheduled to land on the south pole this week but spun out of control on approach and crashed on Sunday.

The south pole - far from the equatorial region targeted by previous missions, including the crewed Apollo landings - is full of craters and deep trenches.

Both the United States and China have planned missions to the south pole.