Gravity Assist Maneuver

The Gravity Assist Maneuver (also known as a gravitational slingshot, gravity assist maneuver or simply swing-by) is a term used in aerospace technology when the satellite uses the gravity of a celestial body (Earth, Moon or the Sun) to change the direction profile and moving of a spacecraft.

What is Gravity Assist Maneuver?

• The Gravity of a celestial body is used to accelerate a spacecraft to either increase or decrease the speed of the spacecraft or to reorient its direction.
• The “gravity assist” is provided to the spacecraft by the motion of the gravitating body as it exerts gravity on the spacecraft.
• The GAM saves spacecraft propellant and hence reduce launch expenditure.
• The reversibility of planetary orbits allows for the gravitational slingshots to be used for reducing the speed of a spacecraft. This is generally used when a spacecraft is nearing its target and has to slow down.

Why is this in the news?

India’s Mission to the moon, the Mangalyaan used a gravity assist to reach Mar’s orbit. This is demonstrated in the movie Mission Mangal when the protagonist uses boiling oil to show that how a spacecraft can continue to move in the space even after its propellants and reaction control sites are switched off.

Practices like the Gravity Assist Maneuver enabled the Mangalyaan to expend less fuel and reach Mars by burning less propellant. This reduced the launch cost and enabled India to send one of the cheap inter-planetary missions.