SpaceX is slated to send its first full astronaut crew to space on Sunday. Watch it live.

By Susie Neilson

SpaceX has secured its Crew Dragon spaceship to the top of a Falcon 9 rocket, and the launch system is ready to roar to life. On Sunday, the company is scheduled to send a crew of four NASA astronauts to the International Space Station.

The mission, called Crew-1, will be SpaceX's first full-length mission for NASA — the first of six that Elon Musk's rocket company has contracted with the space agency. The launch will also mark the true start of NASA's commercial spaceflight program, a milestone nearly 10 years in the making. 

Although the launch was scheduled for Saturday, NASA officials delayed it to Sunday at 7:27 p.m. ET due to issues with "onshore winds and first-stage booster recovery readiness," according to an agency blog post.

The crew consists of NASA astronauts Mike Hopkins, Victor Glover, and Shannon Walker, as well as Japan Aerospace Exploration Agency astronaut Soichi Noguchi. Their Crew Dragon space capsule will launch from the Kennedy Space Center in Cape Canaveral, Florida.

Because of the relative positions of the spaceship and space station, the one-day delay means that although the astronauts' journey will now take 27 hours instead of eight-and-a-half.

Once they dock to the ISS, the team is expected to stay there for six months – making their mission the longest human spaceflight ever launched from the US.

"We are ready for this launch. We are ready for the six months of work that is waiting for us on board the International Space Station, and we are ready for the return," NASA astronaut Mike Hopkins, who will command the mission, told reporters in a call on Monday.

Watch the Crew-1 launch live

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SpaceX's Crew Dragon spaceship sits atop a Falcon 9 rocket in preparation for the launch of Crew-1 at the Kennedy Space Center in Cape Canaveral, Florida, November 12, 2020.

If Sunday's weather doesn't delay the launch again and everything goes smoothly during pre-launch checks, nine Merlin engines will lift the Falcon 9 rocket — with SpaceX's Crew Dragon spaceship on top — off the launch pad. Once the rocket's first-stage booster has burned most of its fuel, it will fall away and land on a drone ship. The rocket's second stage will continue on, helping propel the ship toward orbit and the ISS.

NASA plans to broadcast the launch and docking live via NASA TV. You can watch via embedded video stream below. 

The Crew Dragon is scheduled to dock with the ISS starting at about 11 p.m. ET on Monday. 

'The next era in human spaceflight'

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NASA astronauts Bob Behnken and Doug Hurley.

Although Crew-1 will be SpaceX's first full-length mission, the company launched people into orbit earlier this year. In May, SpaceX flew NASA astronauts Bob Behnken and Doug Hurley to the ISS for a demonstration mission called Demo-2.

Following a smooth launch and docking, the astronauts stayed on the space station for 63 days. Then they took a fiery plunge through Earth's atmosphere in the Crew Dragon before splashing down in the Gulf of Mexico. 

"It felt like we were inside of an animal," Behnken said of the 17,500-mph dive. 

Prior to that mission, astronauts had not flown to space from US soil since 2011, when NASA ended its Space Shuttle program. In 2010, the agency began funding the Commercial Crew Program, a series of competitions between private companies meant to foster a new commercial spaceflight industry. The government has spent over $6 billion on Commercial Crew since it began, according to The Planetary Society

NASA Administrator Jim Bridenstine hailed Demo-2 as evidence of the Commercial Crew Program's success.

"This is the next era in human spaceflight, where NASA gets to be the customer," Bridenstine said in August. 

Dave Mosher and Morgan McFall-Johnsen contributed reporting.