On Friday, April 8, Elon Musk’s SpaceX made history by landing the first stage of an orbital rocket on a floating barge for the first time. Musk deservedly received plaudits far and wide, from Buzz Aldrin to President Barack Obama, but why is a barge landing so important for the company?

Well, it all comes down to reusability. In an effort to make space travel more affordable, by a factor of as much as 100, the company wants to reuse the Falcon 9 rockets it sends to space in a similar manner to how we reuse airplanes rather than scrapping them after each flight. It costs as little as $200,000 to fuel the Falcon 9, but $60 million to make the rocket.

The first step towards this goal was made in December 2015, when SpaceX landed the first stage (essentially the bottom half) of a Falcon 9 on the ground at Cape Canaveral in Florida. Landing on a barge instead, though, opens up a new array of landing possibilities for the company.

To land the first stage, it rotates at an altitude of more than 100 kilometers (62 miles) and reignites its engine, reducing its speed from more than 8,000 kilometers per hour (5,000 miles per hour) to ultimately zero back on the ground. To do this requires quite a bit of fuel, and for regular missions to low-Earth orbit – such as this Dragon cargo flight (with the an exciting inflatable module on board) to the International Space Station (ISS) – that doesn’t pose a problem.

 

 

^{Check out the landing in 4K resolution above. SpaceX}

But for more ambitious launches, landing on the ground isn’t an option. In particular, launches to higher orbits – such as geostationary orbits, or missions beyond Earth orbit (such as to Mars, an ultimate goal for SpaceX) – require a much higher velocity, and thus there is less fuel available for a landing.

On these missions, more fuel is needed to lift the spacecraft or satellite on the rocket to its intended height or velocity. So, by using a barge, SpaceX can return the first stage of the rocket to a location much further out than the launch site. For example, all launches from Florida head East over the Atlantic Ocean; having a barge in the sea means the rocket has less far to travel back to perform a landing.

"For half our missions, we will need to land out to sea," said Musk in a press conference after the launch. “Anything beyond Earth is likely to need to land on the ship.”

^{The Dragon spacecraft successfully docked with the ISS on Sunday. NASA}

With this latest mission, the rocket will be returned on the barge (named "Of Course I Still Love You" in honor of the works of Iain M. Banks) to Cape Canaveral. The first-ever ground landing by SpaceX in December will become a museum piece, but this latest landed rocket will fly again. Ultimately, SpaceX wants to reuse first stages tens of times or more.

"We'll bring the rocket back to Port Canaveral on Sunday and fire it 10 times in a row on the ground," Musk said. "If things look good then it is qualified for reuse and launch. We're aiming for relaunch around May or June – let's say June to recalibrate timing expectations."

Eventually, the company also wants to make the second stage of the rocket – the part that boosts the payload to its orbital velocity – reusable too, bringing the cost of launching down even further. And SpaceX are doing all this in style, with huge public attention surrounding every launch and landing attempt. 

"We’ll be successful, ironically, when landings become boring," joked Musk. For now, the company is continuing to shake up the rocket business – and this barge landing is the latest in a string of successes for the company that could herald an era of affordable space travel.