Now playing: Watch this: SpaceX's Crew Dragon spacecraft docks with the International...

NASA/SpaceX

SpaceX has taken another small step toward sending astronauts into space after launching the Crew Dragon capsule early Saturday morning and successfully docking with the International Space Station.

SpaceX

Affixed to the top of a Falcon 9 booster, the rounded cone capsule of the Crew Dragon blasted off in a blaze of fire and smoke from Kennedy Space Center in Florida at 2:49 a.m. ET Saturday. The launch was the first step in the Demo-1 mission, designed to test the capabilities of the capsule over the next week, but it was only the beginning.

After launch the capsule coasted to the ISS, making a number of maneuvers to line up with a specialized docking adapter aboard the station. Though live footage of the event appeared low-key, both the Crew Dragon and the ISS were traveling at over 17,500 miles per hour during the monumental docking attempt.

Crew Dragon achieved soft capture with the ISS at 5:51 a.m. ET, but the high-speed space grab wasn't over. Shortly after, 12 hooks reached out from Crew Dragon to firmly attach it to the ISS, enabling a "hard capture" of the capsule at 6 a.m. ET and marking the first successful docking of a Commercial Crew capsule at the ISS.

Now playing: Watch this: SpaceX's Crew Dragon launches to the ISS

No humans are on board, but the capsule isn't empty. Locked within Crew Dragon is a flight dummy nicknamed Ripley and an anthropomorphic plushie of planet Earth designed to indicate when the capsule had reached zero gravity. In addition, the capsule carried around 400 pounds of crew supplies and equipment to the ISS to simulate future missions.

SpaceX/NASA

On Saturday morning, the historic launch was celebrated with cheers and applause at Kennedy Space Center, after multiple delays pushed the maiden flight back from an expected launch in 2018. The site of the landmark launch was Pad 39A, which has previously seen NASA's Saturn rockets carry astronauts to the moon aboard Apollo spacecraft and the famous launches of NASA's space shuttles.

SpaceX CEO Elon Musk expressed his appreciation for both the SpaceX team and NASA at a post-launch press conference but noted the mental toll the experience had on him. "To be frank, I'm a little emotionally exhausted," he sighed. "That was super stressful, but it worked... So far."

Though the launch was a success, SpaceX still has a few more obstacles to overcome before the demonstration mission is complete. The capsule will remain docked at the ISS until March 8, then begin what is arguably the most important part of its demonstration: successfully returning to Earth. The capsule is fitted with enhanced parachutes and is set to splash down in the Atlantic Ocean.

SpaceX

Speaking of the Atlantic, the reusable Falcon 9 booster that launched Crew Dragon landed on the droneship Of Course I Still Love You drifting in the ocean, approximately 10 minutes after liftoff.

As part of its Commercial Crew program, NASA handed contracts to both SpaceX and Boeing in 2014 to develop rockets that could send astronauts back to space. NASA hasn't launched humans to space since 2011, when the Space Shuttle program ended. In the meantime, the agency has paid for spots on the Russian-built Soyuz spacecraft at a cost of over $80 million per seat. That makes Saturday's success particularly important, helping chart a course for NASA to bring launches back to American soil and keep costs down.

"We want to make sure we keep our partnership with Russia, which has been very strong for a long period of time," NASA Administrator Jim Bridenstine said before the flight. "But we also want to make sure we have our own capability to get back and forth to the International Space Station."

SpaceX

The Crew Dragon capsule is an enhanced version of SpaceX's Dragon capsule, which has ferried cargo from Earth to the ISS on 16 previous occasions. This iteration can carry seven human passengers, which it'll eventually shuttle to the ISS in low Earth orbit. Provided this demo mission proceeds as planned, the Crew Dragon will have to demonstrate its safety in one more "in-flight abort test," scheduled for later this year.

If it passes that test, SpaceX and NASA will finally be ready to make another giant leap, sending astronauts to the ISS from the US for the first time since 2011.

Originally published March 2, 12.01 a.m. PT.

Updates, March 2, 5:32 p.m. PT: Adds tweets, images from launch; March 3, 3 a.m. PT: Adds ISS docking information.