Chandrayaan3’s slingshot route to the moon

Subject : Science and technology

Concept :

Besides, Chandrayaan3, like its predecessor Chandrayaan2, will take a rather intriguing route to the moon. It will circle the earth five six times, to get the slingshot effect.
It will likewise circle the moon 56 times before the lander began its descent on to the moon’s surface.

Sling shot Effect

The slingshot effect is also known as a planetary swing-by or a gravity-assist manoeuvre.
It is performed to achieve an increase in speed and/or a change of direction of a spacecraft as it passes close to a planet.
As it approaches, the spacecraft is caught by the gravitational field of the planet, and swings around it.
The speed acquired is then sufficient to throw the spacecraft back out again, away from the planet.
By controlling the approach, the outcome of the manoeuvre can be manipulated and the spacecraft can acquire some of the planet’s velocity, relative to the Sun

Why Sling Shot effect in Chandrayaan 3?

To use the earth’s gravity to impart enough velocity to the spacecraft to shoot off to the Moon. In other words, the earth’s gravity does some of the function of the rocket fuel.
Kepler’s Second Law of planetary motion says the line connecting a satellite and the parent body sweeps equal areas in equal intervals of time.
This means that as the satellite gets closer to the parent body, it acquires more velocity. And the farther the object comes from, the higher the velocity it acquires when it turns around the parent body.
After the LVM3 puts Chandrayaan3 above the earth, the spacecraft will start circling the earth on its own, in an elliptical orbit.
When it reaches the farthest point, ground engineers will nudge it slightly to change the direction a little so that its next loop is bigger than the first.
So, when the spacecraft approaches the earth on its second loop, it will acquire a higher velocity.
Again, when it reaches the farthest point, called apogee, the engineers will once again change the direction a little, so that on the third loop, the spacecraft acquires an even higher velocity.
So on for 56 laps, at which point the spacecraft would have acquired enough velocity to sling itself towards the moon.
When it is about 100 km from the moon’s surface, the lander will detach itself and begin its descent.
On reaching the moon, the reverse will happen.

Chandrayaan­3’s sling­shot route to the moon