Reusable Rockets: How Do They Work | Let’s Simplify

On March 30th 2017, SpaceX achieved the world’s first commercially viable reflight with the reusable Falcon 9 rocket. In Europe, ArianeWorks is working on the same goal and in India, ISRO is working on ADMIRE, a reusable satellite launch vehicle similar to the reusable Grasshopper booster rockets from the SpaceX Falcon 9. The project involves a reusable rocket complete with landing legs and steering fins. Let’s explore what reusable rockets are and why all the space agencies are racing to develop the technology.

What Are Reusable Rockets?

A commercial aircraft

Imagine that commercial aircraft could be flown only once. One of the world’s most popular commercial aircraft, the Boeing 747, costs $153 million to make. It’s imperative why we can affordably fly from one place to the other because such aircraft are reusable.

The rockets which carry various payloads like satellites, spacecraft and people to space use and throw. Building these complex launch vehicles is definitely not cheap and developing the technology to reuse them can greatly reduce the cost of getting to space.

How Do Reusable Rockets Work?

SpaceX Falcon 9 reusable rocket
SpaceX Falcon 9 Launch

Let’s be honest. Sending rockets to space is rocket science. Getting them back to Earth in one piece for reuse is hyper rocket science. Still, there are some aspects of the process that can be understood easily. Let’s take the example of Falcon 9, a two-stage rocket built by SpaceX, whose first stage carries the rocket to an altitude of about 100 km – just on the edge of space. Here the second stage separates and fires its own single-engine to take the payload into orbit. The first stage returns to Earth.

The re-entry involves two very interesting modules among the many – the grid fins and the landing legs.

The First Stage Returns…

During re-entry, the falling first stage needs to fire its boosters once again to slow down its fall and gain back control. To some extent, at least. Just slowing it down won’t work, you’ll need to steer it to the landing location too! This is where the heat resistant grid fins pop out from the sides of the booster. They make minute movements to help steer the rocket towards the landing pad.

Falcon 9's First Stage landing on Drone Ship at sea
Falcon 9’s First Stage Landing on Drone Ship at sea

The onboard computers help processing data fed to it from at least a dozen sensors on the craft’s orientation, position, velocity, acceleration and altitude. Just before touchdown, the four legs made of strong lightweight carbon fibre, deploy to absorb the impact with their powerful shock-absorbing system.

It’s All About Efficiency

“The bottom of the ocean is a rocket graveyard – littered with the expended shells of thousands of rockets used to send satellites, and people, to space.” says Cathal O’Connell in a Cosmos article.

Having the technology to be able to reuse the launch vehicles is a significant advantage. It’ll help organizations like ISRO cut down on their operational costs and will be a big boost for their endeavours of sending Indian astronauts to space. We can’t wait for the day the first ISRO launch vehicle successfully touches back down on Earth!