SpaceX will launch NASA astronauts for the 1st time today. Here's what to expect.

UPDATE: SpaceX's first attempt to launch the Demo-2 mission on Wednesday (May 27) was scrubbed due to bad weather. The next launch try will be on Saturday (May 30) at 3:22 p.m. EDT (1922 GMT).

SpaceX is poised to make history today (May 27).

The company's first-ever crewed mission, a test flight called Demo-2, is scheduled to launch at 4:33 p.m. EDT (2033 GMT) from NASA's Kennedy Space Center in Florida. 

You can watch the liftoff — the first crewed orbital launch from the United States since NASA grounded its space shuttle fleet in 2011 — live here and on the homepage, courtesy of NASA, or directly via the space agency.

"We are once again launching American astronauts on American rockets from American soil," NASA Administrator Jim Bridenstine said during a news conference yesterday (May 26). "This is a big moment in time. It's been nine years since we've had this opportunity."

Related: How SpaceX's Crew Dragon Demo-2 mission will work in 13 steps

Weather in Florida is a bit of a concern. There's a 40% chance that clouds and foul weather will keep SpaceX on the ground. If that happens, NASA and SpaceX will have to wait until Saturday (May 30) to try again. 

A SpaceX Falcon 9 rocket stands ready to launch a Crew Dragon spacecraft with NASA astronauts Bob Behnknen and Doug Hurley from Pad 39A of NASA's Kennedy Space Center in Cape Canaveral, Florida on May 27, 2020. (Image credit: NASA/Joel Kowsky)

Demo-2 will send NASA astronauts Bob Behnken and Doug Hurley to the International Space Station (ISS). The mission is designed to fully validate SpaceX's Crew Dragon capsule and Falcon 9 rocket for human spaceflight, so the company can begin flying operational crewed missions for NASA.

SpaceX signed a $2.6 billion contract with NASA in 2014 to complete six such missions, the first of which will lift off shortly after Demo-2 lands, provided all goes well with the test flight. NASA inked a similar, $4.2 billion deal at the same time with Boeing, which the aerospace giant will fulfill using its CST-100 Starliner capsule.

NASA wants these private vehicles to end American dependence on Russian Soyuz spacecraft, which have been astronauts' only ride to and from orbit since the shuttles were grounded. And Demo-2 brings that goal within reach at long last.

Today's liftoff will also mark the first crewed debut of an American orbital spacecraft since April 1981, when the shuttle flew its initial space mission. And Crew Dragon will be just the fifth U.S. vehicle, and the ninth overall, to carry astronauts to Earth orbit or beyond.

So, yeah: Demo-2 is a pretty big deal. President Donald Trump is even going to attend. 

Related: Here's every spaceship that's ever carried an astronaut into orbit

After launching today, Crew Dragon will spend 19 hours chasing the space station down. The capsule is scheduled to dock with the orbiting lab tomorrow (May 28) at 11:39 a.m. EDT (1539 GMT), and the hatches between the two craft will open about 2.5 hours later. 

Behnken and Hurley will then float aboard the space station, kicking off a stay of unknown duration. Demo-2 will last between 30 days and four months, NASA officials have said; the end date will be determined later, after mission team members have had a chance to assess Crew Dragon's performance and the readiness of the capsule that will fly Crew-1, SpaceX's first operational human spaceflight mission.

Starliner isn't ready to fly astronauts yet, by the way. The Boeing capsule failed to meet up with the ISS as planned during its uncrewed Orbital Flight Test (OFT) in December 2019. (SpaceX successfully completed its version of this mission, called Demo-1, in March of last year.) Starliner will refly OFT before welcoming crewmembers aboard, and it's unclear at the moment when that makeup mission will launch.

And a quick note about milestones: Today's launch will not be the first human spaceflight of any sort to launch from the U.S. since the shuttles' retirement. 

The space tourism company Virgin Galactic has launched two piloted test flights to suborbital space from California with its VSS Unity spaceliner, once in December 2018 and again in February 2019. VSS Unity is a suborbital vehicle, so it's not designed to make any loops around Earth.

Visit for complete coverage of SpaceX's Crew Dragon Demo-2 flight. 

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook

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Mike Wall
Senior Space Writer

Michael Wall is a Senior Space Writer with and joined the team in 2010. He primarily covers exoplanets, spaceflight and military space, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.