Update for 6:19 pm ET: SpaceX has successfully launched the private Ax-2 astronaut mission to the International Space Station. Read our launch wrap story and see video and photos.
SpaceX is counting down to launch the second all-private mission to the International Space Station today (May 21) and if you're hoping to follow it online, you're going to need to know when it actually lifts off.
A SpaceX Falcon 9 rocket will launch four astronauts on the Axiom Space Ax-2 mission to the space station from NASA's Kennedy Space Center in Cape Canaveral, Florida. The 10-day mission is commanded by former NASA astronaut Peggy Whitson, with paying customer John Shoffner as pilot and Saudia Arabia's first two astronauts , Ali AlQarni and Rayyanah Barnawi, rounding out the crew.
You can follow the launch live with our Ax-2 mission updates page and watch the Ax-2 astronaut launch live online. Read on to see what time SpaceX will launch the Ax-2 mission today
What time is the SpaceX Ax-2 astronaut launch?
SpaceX will launch the Ax-2 mission for Axiom Space at 5:37 p.m. EDT (2137 GMT) from Pad 39A at NASA's Kennedy Space Center, the site used by the company for all of its human spaceflight missions.
The launch has an "instantaneous window," meaning SpaceX must launch at that time in order to reach the International Space Station on schedule and cannot hold the countdown. If SpaceX has to delay for any reason, the company can try again on Monday, May 22, at 5:14 p.m. EDT (2114 GMT).
Related: Meet the 4 astronauts of Axiom Space's Ax-2 mission
Can I watch the Ax-2 astronaut launch online?
Yes. NASA, SpaceX and Axiom Space will offer a series of live webcasts for the public to follow the Ax-2 launch live. You can watch the SpaceX Ax-2 launch online in a Space.com simulcast of those webcasts.
SpaceX's webcast will begin around 2:10 p.m. EDT (1810 GMT) and run through liftoff. You can find it at SpaceX's Ax-2 mission page and YouTube channel. The company will also offer an audio-only feed from its launch center in Florida and Mission Control center in Hawthorne, California.
Axiom Space's launch webcast begins at the same time and may be a simulcast. It will stream live at Axiom's YouTube channel. Axiom Space has also said it will provide an Arabic language livestream for Saudi Arabia viewers tracking the launch.
NASA's webcast will begin at 4:30 p.m. EDT (2030 GMT) and cover the last hour of prelaunch operations and the liftoff. It will be broadcast on NASA's YouTube channel and NASA TV.
How long is SpaceX's Ax-2 astronaut launch?
From liftoff to spacecraft separation, SpaceX's Ax-2 mission launch should last just under 13 minutes, but the mission itself will last much longer.
Axiom Space's Ax-2 astronauts will fly a 10-day mission to the International Space Station and are expected to spend eight of those days actually living and working aboard the space station, where they will perform 20 different science investigations amid other tasks and outreach events. It will take 15 hours for the Dragon capsule, called Freedom, to reach the space station on Monday, May 22.
SpaceXs final hour before launch includes a series of critical tasks to get the rocket ready to fly. Here's the schedule SpaceX will follow to reach liftoff, including fueling the Falcon 9 rocket with its RP-1 rocket-grade kerosene and liquid oxygen (LOX) propellant.
Related: Ax-2 private astronaut mission will grow 1st stem cells in space
One the Falcon 9 rocket carrying the Ax-2 mission lifts off, that's when the 13-minute trip to orbit begins. Here's a rundown of how that will work for this flight, including first and second stage main engine cutoffs (MECO).
What if SpaceX's Ax-2 mission can't launch on time?
SpaceX has an instantaneous window in which to launch the Ax-2 mission, so if it cannot liftoff on May 21 at 5:37 p.m. EDT for any reason, it will have to be delayed at least one day.
There is a backup launch opportunity on Monday, May 22, at 5:14 p.m. EDT (2114 GMT), that SpaceX could use to launch the Ax-2 astronauts, but weather may be a concern. U.S. Space Force officials have said that poor weather moving in early Monday means the launch has just a 20% chance of good conditions for flight.
If SpaceX is unable to launch the Ax-2 mission for Axiom Space by May 22, the timeline gets a bit more complicated and may lead to a lengthy delay.
NASA currently expects SpaceX to launch an uncrewed Dragon spacecraft on the CRS-28cargo mission on June 3, and plan to give that mission priority if Ax-2 can't lift off this week. Meanwhile, SpaceX rival Boeing is planning to launch its first crewed flight of its Starliner spacecraft in July, a mission that is also a high priority for NASA.
"If we don't get off on Sunday, Monday we'll get together with NASA and Axiom and SpaceX and kind of look at the whole manifest and see what the next opportunity is for launch opportunity for the Axiom 2 mission," NASA space station manager Joel Montalbano said Saturday.
