Retro Propulsion - The way rockets propel back

Rockets are known for making their way up into sky off to space but have you ever noticed a rocket land? Recent technological advancements have proven that rockets too can land. Blue origin‘s New Shepard rocket was the first to officially land a rocket on November 23, 2015. 

Video Credits: Everyday Astronaut

SpaceX commercially implemented the idea in their Falcon Boosters. Since then several rocket landings were witnessed. So what’s the technique, that can be used to make a rocket land? Conventionally parachute was typically used to decelerate space vehicles while successful re-entry but they cannot land a rocket to a precise location. 

What about employing propulsive devices! Wait isn’t propulsive device used to propel rockets upwards, how can they be utilised to do the exact vice versa of their functional operation? Turns out we can implement propulsion to decelerate and on top land to an exact location using Retro propulsion.

Retro propulsion is a technique in which the rocket engines are fired against the velocity vector to decelerate the vehicle and bring the vehicle to rest. It may seem to be new in the industry, yet it isn’t, the same technique is used in space vehicles (Lander’s) to land on other planet surfaces, commonly known as “retro rockets.“

Vehicles which utilise retro propulsion are categorised under VTVL (Vertical Take-off and Vertical Landing) rockets. But profound significance was only identified once the modern technique was applied to reusable launch vehicles which progressively expanded the operational capability of rockets i.e. not only to launch but also to land gently.

What’s the considerable significance in landing a rocket? Well landing a rocket invariably makes it reusable, which typically reduces the launch cost by 30% (A PSLV launch costs around ₹100 crore). A rocket booster can be re-used up to five times by just refilling it, this enables low cost space accessibility. Who knows retro propulsion may help land our personal space vehicles at our backyard in the upcoming future.

"Though it looks like a rewind of launch video, its actually the Merlin engines thrusting down"