Chandrayaan-3 vs. Apollo 11: Time to Reach Moon

The Indian Space Research Organisation (ISRO) utilized its heaviest rocket, the Geosynchronous Satellite Launch Vehicle (GSLV) Mark-III, to put the Chandrayaan-3 propulsion module, carrying the lander, into an elliptical orbit around the Earth.

Chandrayaan-3’s Journey to the Moon:

Orbit Raising Maneuvers:

Over the next two weeks, ISRO will conduct between five to six orbit raising maneuvers.
These maneuvers will be carried out using the onboard propulsion system.
With each burn of the propulsion system, the module will spiral outwards in increasingly elongated ellipses.

Achieving Escape Velocity:

The speed of the propulsion module will steadily increase during the orbit raising maneuvers.
This speed increase is necessary to reach the escape velocity required to break free from Earth’s gravity.

Lunar Transfer Trajectory (LTT):

Once the propulsion module reaches the escape velocity, it will enter a Lunar Transfer Trajectory (LTT).
This trajectory will set a course for Chandrayaan-3 towards the moon.

Translunar Injection:

The critical moment of Translunar Injection will occur on 1 August.
Translunar injection is when Chandrayaan-3 will leave Earth’s orbit and begin its journey towards the Moon.

Projected Landing Date:

The anticipated landing date on the lunar surface is projected to be around 23 August.
This landing will occur over three weeks after the Translunar Injection.

Final Steps:

After over 40 days from the launch and several orbital maneuvers, the lander will finally reach the surface of the Moon.
Once on the Moon, the lander will deploy the rover, commencing its exploration mission.

Why Chandrayaan-3 Takes Weeks to Reach the Moon?

The simple answer is because ISRO does not have a rocket powerful enough to put Chandrayaan-3 on a direct path to the Moon.Following are also reasons for delayed of Chandrayaan-3 Journey:

Difference in Trajectories:

Previous missions like China’s Chang’e 2 and Chang’e 3, the Soviet Union’s Luna-1, and Apollo-11 used direct trajectories called Translunar Injection (TLI).
Direct Translunar Injection involved a powerful engine burn to send the spacecraft directly towards the Moon, allowing them to reach the Moon relatively quickly within a few days.

ISRO’s Rocket Capability:

Chandrayaan-3 is following a different trajectory due to the lack of a rocket powerful enough for a direct path to the Moon.
ISRO’s current launch vehicles cannot execute a direct TLI like the Saturn V used in Apollo missions.
While the GSLV Mk-III is a capable launch vehicle, it does not have the same power and payload capacity as the Saturn V used in the Apollo missions.
As a result, a more gradual trajectory was chosen to optimize the mission within the constraints of the launch vehicle.

Earth Orbits and Engine Burns:

Chandrayaan-3 employs a series of Earth orbits and engine burns to gradually increase its speed and position for lunar insertion.

The spacecraft enters an initial Earth orbit and performs engine burns at specific times to transfer to a trajectory intersecting with the Moon’s orbit.
Multi-step approach used by the ISRO for the Chandrayaan and Mangalyaan missions requires more time but allows for the use of a relatively less powerful launch vehicles.

Lunar Insertion:

After the required Earth orbits and engine burns, another engine burn will be conducted to insert Chandrayaan-3 into lunar orbit.
This process takes more time compared to the direct TLI used in previous missions.

Saturn Rocket’s Slingshot Effect:

In contrast to Chandrayaan-3‘s method, the Apollo missions utilized a single six-minute-long burn of the Saturn rocket’s third stage for a slingshot-like effect to direct the spacecraft towards the Moon.

Despite the longer travel duration, Chandrayaan-3’s trajectory remains a feasible approach given ISRO’s current rocket capabilities. The mission aims to achieve lunar orbit and carry out its scientific objectives, contributing to further lunar exploration efforts.

Chandrayaan-3 vs. Apollo 11

Chandrayaan-3’s: Clever Gravity-Assisted Journey to the Moon:

Earth’s Elliptical Orbit and Perigee:

The module orbits the Earth in an elliptical path, with a point closest to the planet called the perigee and a farthest point called the apogee.
At perigee, the module is at its highest speed due to Earth’s stronger gravitational pull.

Utilizing Earth’s Gravity:

Each time the module reaches perigee, the onboard engine fires, increasing its speed even more, and pushing it into a higher, more elongated orbit.

Escape Velocity and Lunar Transfer Trajectory (LTT):

As the module continues its journey, it reaches the escape velocity to break free from Earth’s gravity.
The module’s orbit elongates, enabling it to set a course towards the moon.

Strategic Lunar Orbit Insertion:

The Chandrayaan-3 module’s entry into LTT is precisely timed to align with the moon’s position in its orbit.
A manoeuvre called lunar orbit insertion reduces the module’s velocity and allows the moon’s gravitational field to pull it into a stable lunar orbit.

Orbiting the Moon:

Once in lunar orbit, the module revolves around the moon in an elliptical path.

Lowering Altitude for Lunar Surface:

A series of manoeuvres progressively lower the module’s altitude to place it in a 100 km circular orbit around the moon.

Separation of Propulsion Module and Lander:

At this point, the propulsion module separates from the lander, which continues its journey towards the lunar surface.

Groundbreaking Soft-Landing:

If all goes as planned, around 23 August, Chandrayaan-3 will achieve a groundbreaking feat by becoming the first mission to successfully soft-land near the lunar south pole.

Chandrayaan-3’s innovative use of gravity and precise manoeuvres ensures a successful journey to the Moon and sets the stage for groundbreaking lunar exploration.

Chandrayaan-3 vs. Apollo 11: Time to Reach Moon,Chandrayaan-3 vs. Apollo 11: Time to Reach Moon

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