Why was the gravity slingshot used for Mangalyaan?
Do you know that the humble slingshot was actually used in 2014 in the launching of India’s new satellite, Mangalyaan? In 1981, when India’s space scientists grappled with the challenge of finding a metal-free transportable platform for its new satellite, they turned to a most improbable innovation. As the world watched amazed, Indian scientists wheeled out a gleaming new satellite on a creaking old bullock cart.
Gravity assist, sometimes called an interplanetary slingshot, involves approaching an intermediate planet (not the one you initially start from, or are destined to go to) in a hyperbolic orbit. Because you change direction as you approach and leave the planet, you end up "stealing" a little bit of the planet's momentum on your way by, which is transferred to your spacecraft. This is very clear if you apply some fairly simple vector math to the planet and the spacecraft, both from the sun-centered frame and the planet-centered frame. Math always helps! Anyway, gravity assist can also be used to slow down a spacecraft as it passes a planet.
And, Mangalyaan actually saves fuel by travelling a greater distance. The mission cuts costs by using its resources in the most efficient manner possible. ISRO designed the spacecraft to travel 690 million kilometres between Mars and Earth in a curved manner, even though the straight-line distance is only 55 million kilometres. Though this may seem counter-intuitive, it has actually been critical to minimising Mangalyaan’s fuel usage, because by using a smaller rocket to put its spacecraft into Earth orbit first, it gained enough momentum to slingshot toward Mars.
Find out about all the ways the innovative scientists at ISRO cut down their costs?