The Final Lunar Descent: Why Is It Risky?

Sep 18, 2019 By Aaditi P, Writer
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The final descent onto the Moon is known for being a notoriously treacherous incline for space landers looking for a safe spot to land.

On September 6, India’s Vikram lunar lander crashed into the rocky terrain of the Moon in an attempt at a soft landing to complete the country’s $140 million Chandrayaan-2 mission. 

The news of the failed landing came just months after the crash of an Israeli lander on the surface of the Moon. Both landers suffered a similar fate as they lost communications with their respective space centers in the final stages of descent.

Lunar Orbiters and Landings

One of the greatest lunar successes lies in the Apollo 11 mission - but the story of its risky landing is little known. Just before touching onto the surface of the Moon, Mission Control was busy grappling with unknown errors regarding interference of communications between the computers and the lander’s radar. This caused scientists to realize that the lander was taking the crew to a crater filled with boulders.

Because of this error, astronaut Neil Armstrong halted descent and manually flew the lander to find a smooth landing area. In a timeframe of a few, nail-biting minutes, all that flight control could do was listen as Buzz Aldrin called out the changing altitudes and as the gas tank dropped in levels. Finally, Armstrong softly touched down and famously replied, “Houston, Tranquility Base here. The Eagle has landed,” to mission control.

Why is the final 300-foot descent the most perilous part of the 240,000-mile journey? To begin its descent, a lunar lander propels itself out of the moon’s orbit towards the surface of the moon. As it gets closer and closer to the rocks and craters of the moon, the lander is continuously programmed and reprogrammed to make the safest landing.

In these last minutes of terror, the lander has to slow down by tenfold as it makes a soft landing on the surface of the moon. As the lander approaches the Moon, it also has to deal with the uneven gravitational pull. When it comes down to the final descent, it is a hit or miss for the lander - with the possibility of succeeding or ending catastrophically.

What Went Wrong?

As previously mentioned, to successfully land, a lunar lander has to find a safe landing spot and significantly reduce its speed. However, just before the final miles, India’s space control lost communications with the lander and later, an error in a command that was supposed to shut off one of Vikram’s engines was discovered. As a result, the Vikram lander hurtled towards the surface at 110 mph, when it was supposed to touch down lightly at a speed of 5 mph. 

Similarly, the Israeli nonprofit lander that crashed on the moon lost communications with the command station and a technical glitch caused a malfunction in the spacecraft’s engine - leading the spacecraft to plummet to the rocky terrain at 310 mph.

Despite the disappointment at not achieving two more lunar landings this year, scientists are treating the failures as a lesson and an opportunity to better space technology. Let's look at this inspirational Apollo 11 landing to understand how challenging a lunar mission is.

Sources: NYTimes, NASA, BBC, CBS, Space.com, BusinessInsider.com