Elon Musk and one of SpaceX's self-landing Falcon 9 rocket boosters. Samantha Lee/Business Insider; SpaceX/Flickr; Getty Images

Elon Musk has just pulled off his dream of more than 15 years: fuel up a used rocket booster, fire it off, then recover it for yet another launch.

"It's an amazing day for space as a whole, for the space industry," Musk said during a live broadcast of the launch.

SpaceX, Musk's rocket company, launched one of its 229-foot-tall Falcon 9 rockets at 6:27 p.m. on Thursday. The two-stage rocket delivered a telecommunications satellite into orbit.

But the biggest moment came minutes after launch, when the first-stage booster fell back to earth.

The rocket's booster is the largest and "most expensive part of the rocket," Musk said, and the one used Thursday had launched and landed itself on April 8, 2016.

That booster on Thursday again detached from its payload, fell back to earth, and safely landed on a drone ship in the Atlantic Ocean.

The event marks the first time that any part of a commercial, liquid-fueled orbital rocket has been successfully recovered, reused, and recovered again.

"This is going to be a huge revolution for spaceflight. It's been 15 years to get to this point," Musk said. (SpaceX was founded in 2002.) "I'm at a loss for words."

Why this launch was so important

The main mission of the launch was to get a satellite called SES-10 into orbit more than 22,000 miles above Earth. From there, it will blanket much of Central America and South America with internet and television coverage.

But all eyes were on the first-stage booster.

Boosters ordinarily cost tens of millions of dollars to build, yet always burn up, sink into the ocean, or crash to the ground after helping deliver a payload into orbit.

But not so for the bottom halves of most 229-foot (70-meter) Falcon 9 rockets. Those boosters can touch down on land or on a ship at sea. Until Thursday, however, SpaceX had not relaunched one to prove its scheme works.

John Logsdon, a space-policy expert and historian at George Washington University's Space Policy Institute, told Business Insider before the launch that the feat — now a fact — could be "potentially revolutionary," since reusing boosters could reduce the steep cost of getting to space.

"Reusability has been the holy grail in access to space for a long, long time," Logsdon said.

Falcon 9 launches, now 30% off?

The main parts of SpaceX's partly reusable Falcon 9 rocket system. SpaceX/Flickr; Business Insider

The booster for the SES-10 mission first fired on April 8, 2016. It helped deliver an inflatable room to the International Space Station, screamed back to Earth, righted itself, and landed on a drone ship in the Atlantic Ocean.

Gwynne Shotwell, SpaceX's COO, has said that reusing a rocket booster could save customers about 30% on a $62 million Falcon 9 rocket launch. The Falcon 9 is already the most affordable orbit-capable rocket system in the world, but such a discount could save companies more than $18 million per launch.

"This mission ... is the fundamental key demonstration," Shotwell said in a video before Thursday's launch. "It will allow people to live on other planets," she said, referring to Musk's ambitious vision to colonize Mars.

Markus Payer, the global communications director for SES, the telecommunications company behind the new satellite, said the deal to be a part of this historic launch came about in August. The launch was originally planned for later in 2016, but SpaceX's uncrewed rocket explosion on September 1 and the monthslong accident investigation that followed delayed it.

"Wherever we can change the industry equation, we will do it. We were waving our hands to be the first," Payer previously told Business Insider. "We are not risk-averse, otherwise we would not be launching satellites."

Musk was elated by the rocket booster's landing at the center of a drone ship.

"We just had an incredible day today," Musk said. "Right in the bull's-eye."