The Momma Clan

As Chandrayaan-3 is steadily proceeding on its journey towards the moon, carrying hopes of billions of Indians to see the Indian marvel land on the most difficult location on the moon along with it, some questions are being raised on the number of days rather weeks that Chandrayaan is taking to reach its destination. 

It is being discussed that while the American and Chinese missions took just four to five days to reach the moon, why is Chandrayaan taking more than forty days to travel the same distance?

While the Chinese Chang’e 2 took just four days to cover the distance between Earth and the moon and so did Chang’e 3, The Soviet Union’s Luna-1 took just 36 hours and the Apollo-11 command module carrying three astronauts took just over four days after its launch, our Desi Boy is taking weeks to cover the same distance and is freely roaming all around in space before it does the assigned task of reaching the cratered sphere.

The answer is simple, ISRO does not have a rocket powerful enough to put Chandrayaan on the direct path to the moon. 

In case of Apollo mission the Saturn-V launch vehicle propelled the spacecraft into Earth’s first orbit and from there, a powerful six-minute long engine burn was executed to send the spacecraft on a direct trajectory toward the moon (Translunar Injection) enabling a shorter and swift journey whereas Chandrayaan-3 is following a totally different trajectory because though this mission has been launched on India’s heaviest rocket the LVM-III, still this rocket is not powerful enough to propel a payload like Chandrayaan on a direct path to the moon. Hence our Baby has to work harder to achieve its goal. 

In order to counter the lack of such a powerful launch vehicle ISRO has used a complex dynamix of astronomy and physics.

Let us know what is the technology used to conquer this drawback.

To make up for the absence of a powerful launch vehicle, ISRO has chosen a more gradual trajectory, is performing some extra maneuvers, and simultaneously using Earth’s and moon’s gravity to achieve its mission to slingshot Chandrayaan’s way to the moon exactly the same way as it did in Mars Orbiter Mission.

Chandrayaan-3 has employed a series of Earth-bound maneuvers and Lunar orbit insertion burns to gradually raise its orbits and synchronize it with the moon’s orbit using a series of bi-elliptical transfers which involve multiple engine burns to gradually increase the spacecraft’s energy and adjust its trajectory. 

Let us understand this in simple language:

While orbiting around the Earth, the spacecraft achieves the highest speed while passing through the perigee of the Earth (point closest to the Earth) and is at its slowest speed at the apogee of the Earth (point farthest from the Earth) in its orbit and this speed varies at different points in the orbit depending on the Earth’s gravitational pull. The closer the module is to the Earth, the higher its velocity.

Every time the module reaches the perigee an onboard engine is fired increasing its velocity and pushing it higher in a more elongated orbit, hence with every burn of the onboard propulsion system the module keeps spiraling outwards in increasingly elongated ellipses and its speed keeps on increasing gradually until it reaches the escape velocity necessary to break free from Earth’s gravity and enter the Lunar Transfer Trajectory which is timed very carefully and precisely to align it with the moon’s position in its own orbit 

The slingshot in this case is aimed at taking advantage of Earth’s gravity to increase its velocity towards the moon ensuring that the module reaches in proximity to the moon’s orbit when the moon is located in a favorable position.

This part has already successfully achieved by our brilliant scientists on the 1st of August at midnight when the module was put on the Lunar Transfer Trajectory.

Now once the propulsion module will reach the intended point in this trajectory, a precise maneuver will again be executed using the onboard propulsion system known as lunar orbit insertion intended to reduce the module’s velocity and then the moon’s gravitational field will be used to place the module in the stable lunar orbit which will be another significant landmark in the journey of Chandrayaan. 

According to the scientists at ISRO, this Lunar Orbit Insertion is a critical phase and has to be a meticulously planned maneuver for speed reduction. The moon’s elliptical orbit due to which its distance from Earth varies also adds complexities to the mission. 

This is one of the most critical test that Chandrayaan-3 has to pass to secure its place on the Lunar surface because if Chandrayaan-3 fails to be captured by the moon’s gravity, while oscillating between the closest and the farthest points from the earth and enter the orbit, the consequences would be significant. In that case the spacecraft might either crash into the moon or be flung far away from it due to earth’s gravitational pull. 

Well, let’s not even think about it.

Anyway, once it enters the Lunar orbit, it will again start rotating in the Lunar elliptical orbit, where again, a series of maneuvers will be performed to progressively lower the altitude of the module and place it in a 100 km. circular orbit and at this point, the propulsion module will separate from the lander and Vikram, the Lander will continue its further journey and attempt soft-landing in the South polar region of the Lunar surface.

This multi-step approach allows ISRO towards more fuel-efficient and cost-efficient missions and use of less powerful vehicles but takes longer as compared to the direct trajectory used by missions from America, the Soviet Union, and China. 

So shouldn’t the brilliant genius Indian minds who in spite of the shortage of technology, resources, and funds still with their courage and intelligence challenge the world, be saluted for their efforts towards achieving their dream of putting India at the number one position in the world map?

Friends, last time we fell short of just a few seconds but let’s pray for everything to go well this time because if everything goes on as scheduled and planned then on the 23^rd of August Chandrayaan-3 will achieve the feat of becoming the first-ever mission by any country to successfully soft-land in the South polar region of the moon.

In the meantime, let’s keep our fingers crossed, pray and patiently wait to rejoice Chandrayaan’s entry into the Lunar orbit on the 5^th of August, and in between we’ll meet to discuss that why is soft-landing in the south polar region is considered a next-to-impossible task and why has no country till date attempted to send a mission in this region but all eyes are set on Chandrayaan-3 and hoping it to achieve 

THE UNACHIEVABLE

Bye till we meet again!!!

-Ashu Verma Chaubey