SpaceX is about to launch four astronauts in the first commercial human-ranked spacecraft.

This will not be SpaceX’s first human mission. NASA astronauts Bob Behnken and Doug Hurley boarded the company’s Crew Dragon spaceship this summer, launched a rocket into Earth orbit, and docked at the International Space Station. After two months living and working on the space station, they once again boarded the Crew Dragon, screamed into the atmosphere, and parachuted safely back to Earth.

But this entire mission was a demonstration – a critical step for NASA certification for human spaceflight.

NASA announced Tuesday that it has finally certified SpaceX’s full launch system for human spaceflight.

The decision was the result of an agency review of flight readiness, in which experts and officials spent two days reviewing SpaceX’s Falcon 9 rocket, the Crew Dragon spaceship, software, and mission operations.

The certification came just days before the upcoming SpaceX astronaut launch, scheduled for Saturday. The company has already put a new Crew Dragon on the rocket in preparation for that longest and most important mission to date. The mission is called Crew-1, and it’s a round-trip mission to the space station and it’s the first of six missions Elon Musk’s rocket company has contracted with NASA.

“People tend to think it’s just a spacecraft, but it’s a spacecraft, it’s the launch vehicle, all processing operations on Earth, it’s the way you carry out your mission operations. All of this will lead our crew safely to the International Space Station,” said Cathy Lauders, who leads the flight program. Human Space at NASA, at a press conference on Tuesday, “Back Then Recover.” “You showed us the data, and we trust that you do. It’s a big confidence factor here. “

Weather permitting, SpaceX’s Falcon 9 will launch a Crew Dragon into space on Saturday 7:49 PM ET. On board will be astronauts Mike Hopkins, Victor Glover, Shannon Walker and Soichi Noguchi. They should dock at the space station after eight and a half hours, where they will stay for six months, marking the longest human spaceflight in US history.

When it is time to return home, the astronauts will once again climb up to the Crew Dragon, which will remain connected to the space station during their stay, and then face a fiery fall through Earth’s atmosphere.

“The life of the crew is in our hands – a very important responsibility,” said Lauders.

This is the first time that NASA has certified a human flight system since the space shuttle program began nearly 40 years ago. The decision was the culmination of 10 years of development and testing funded through the NASA Commercial Staff Program, which was created to restore human spaceflight capabilities to the United States through commercial partnerships. The government has spent more than $ 6 billion on this effort, he says Planetary Society. The program may finally reach its goal with its Saturday launch.

Musk said in a. “Thank you to NASA for its continued support to SpaceX and the partnership in achieving this goal.” Press release. “I couldn’t be more proud of everyone at SpaceX and all of our suppliers who worked incredibly hard to develop, test, and operate the first commercial human spaceflight system in history to be certified by NASA. This is a great honor that inspires confidence in our endeavor to return to the moon, and travel to Mars, eventually helping mankind to become multi-planet. “