How did India get to the Mars?

Question

A few years back ISRO sent their orbiter to the Mars, It is known to be the biggest feat achieved by Indian Space Research Organization over the years.

It special because ISRO manage to pull this out in an an exceptionally low budget.

2-3 years ago a movie was made called MISSION MANGAL, since it was a bollywood movie, it was hard for me to have faith over the scientific explanations show in the movie (cuz bollywood is infamous of having a loose hand in physics).

It was shown that since ISRO did not have enough budget to make something that would directly go from earth into mars' orbit, they made the orbiter orbit the earth for some time. After every round, when the satellite came back to the perigee, they would fire the fuel in it in order to increase the radius of the orbit of satellite thereby increasing its velocity.

After taking rounds and rounds of earth, at one point after firing the fuel, the satellite would have enough velocity to cross the Van Allen Belt.

Is this thing practically possible? Did ISRO actually use this method to go to the Mars?

Answer 1

The Indian Mangal mission is a big achievement. Getting to Mars is hard, even for a space agency with the budget of NASA. The scientists and engineers at ISRO deserve all the respect for what they have done.

The use of repeated orbit raising manoeuvres is real, but it is not done for budget-saving reasons, but for fuel efficiency, which allows for greater payload.

The Oberth effect means that you get a bigger change kinetic energy by doing a rocket boost when you are travelling quickly (remember "work=force × distance" so if you can apply the same force over a longer distance you'll get more work, and a greater change in kinetic energy)

Satellites move fastest when they are close to the Earth. By doing several rocket burns, you do more of your burn time when you are moving fastest, and this improves the efficiency. You don't need to carry so much fuel and if you save weight on fuel, you can deliver a bigger payload.

The cost is that it takes longer to get to Mars. This is always a compromise. In scientific missions, time isn't so critical, but the scientist do want to put lots of toys in the payload. On the other hand, SpaceX are looking at human transfer to Mars, and plan a quick but inefficient route that requires more fuel, but saves on life-support.

There isn't much financial saving. The cost of fuel for orbital manoeuvres isn't a limiting factor, compared to the cost of development, implementation, launch and the results of the science. However, it did save money in one way: the launch vehicle was only required to deliver the probe to an elliptical Earth orbit, and not an escape trajectory. This allowed the use of an existing Indian PSLV rocket, rather than needing to develop a more powerful launcher.