America reaches the moon in 4 days, but why does India take more than 50 days?

draper.com

The objectives of Apollo Mission and Chandrayaan and the criteria attached to it are different. Where the mission of the Apollo mission was to bring humans to the moon, Chandrayan's objective is to study the moon by delivering scientific instruments.

Now you will ask what is the purpose of time? The distance to the moon is the same! The distance is the same, but the paths are different!

In the Apollo mission, the safety of the passengers was paramount, it was more important to bring all the passengers back to the earth safely - more than reaching the moon. Apollo 1 passengers were killed in a fire at the launch, while Apollo 13 had to be towed back to the moon without a technical malfunction.

Apollo's vehicle had the maximum security and safety of passengers. But due to space constraints, more than a limit could not be kept. In such a situation, it was necessary that the passengers could complete the journey in the shortest time, and the mission could be finished in the shortest possible time. That is why such a way of reaching the moon was calculated which could do this without caring about the rest of the means, and it was implemented.

In contrast, the Chandrayaan does not have a security barrier due to no passenger. In such a way, the most cost-effective (cost-of-operation) means to get the maximum useful equipment (payload) to the moon, so that the return on investment is high, that is, more work for less money.

Path of Apollo -

Apollo was initially orbited at Earth with sufficient velocity, as with every spacecraft. The engines are stopped as soon as the orbit starts in orbit and the orbit continues in the same orbit following the laws of motion. In such an orbit when the vehicle is at its nearest point from Earth, its speed is highest. Upon reaching this point in the Apollo mission, all engines and rockets were restarted with full force, which caused the vehicle to leave Earth's orbit and move towards the moon. Once approaching the moon, the speed of the vehicle was again controlled using rockets, so that the vehicle could reach the orbit suitable for orbiting the moon.

In this way, even if the vehicle reaches the moon quickly, it costs a lot of fuel. But keeping in mind the safety of the passengers, this is the appropriate way. Such a mission also requires a specially made powerful rocket-like Saturn 5, which is not currently owned by any country and its construction is very expensive.

This is the path of Chandrayaan 2 -

Chandrayaan is initially introduced to orbit the Earth, as it does with every spacecraft. When the Chandrayaan reaches the nearest point from the Earth, the rocket will be set off by a very slight burn, which gives a slight increase in the speed of the vehicle. With this effect, Chandrayaan's orbit will increase slightly. Upon reaching the nearest point in the next round of the Chandrayaan, this process will be repeated so that the orbit becomes higher. In this way, the same process will be repeated in every orbit, and at every stage, the vehicle will continue to reach closer to the moon.

In doing so, a time will come when the impact of the moon's gravity on the orbit will be greater than the gravitational effect of the Earth and the moon will start orbiting the moon. Now, by reversing this process, the moon will be lowered slowly to the moon, reducing the speed of the vehicle in each orbit.

In this process fuel consumption is low, mission cost is also low, but because it has so many stages, time takes longer. But with no risk to one's life, and no time constraint, this is the appropriate way to travel to the moon.

This process also does not require specially built, extremely powerful rockets. Chandrayaan 2 is launched with GSLV Mark 3 rocket, which may be India's most powerful rocket to date, but its capacity is 1/10 of Saturn 5.