The launch has finally taken place. The SpaceX Crew Dragon is on its way to the ISS with four astronauts onboard after a successful launch at 7:27 p.m. ET.
You can read everything you need to know about the successful launch here.
But it's been a long time coming. This launch in particular has had a storied journey, with multiple postponements and delays. It was originally supposed to launch way back in 2016.
Here are the answers to your most pressing questions about the mission.
Wait, what was that about the engines?
The targeted launch date for Crew-1 was pushed back from late October after NASA and SpaceX noticed some unexpected behavior from a few Falcon 9 engines that were set to be used for an unrelated mission to launch a military GPS satellite. That mission was scrubbed with just two seconds left on the countdown and an investigation later revealed a stray bit of lacquer had clogged a tiny relief valve line. The clog caused two of the rocket's engines to try and fire early, potentially damaging the engines had liftoff not been automatically aborted.
SpaceX found that engines in the rocket to be used for Crew-1 had the "same tendencies." Launch date was moved to November, the engines were swapped out and now NASA and SpaceX are both satisfied that it's go time.
OK, so why is Crew-1 a big deal?
Crew-1 is part of the culmination of NASA's Commercial Crew program that's been years in the works. For decades, NASA has typically developed its own rockets and spacecraft internally with the help of contractors, but the Commercial Crew program works more like chartering a flight. Companies like SpaceX and Boeing have vehicles designed to be used by other customers, and NASA can hitch a ride on them.
It's also a huge step in bringing spaceflight back to US soil. From the end of the Space Shuttle program in 2011 up until the Demo-2 mission that sent two NASA astronauts to the ISS aboard a Crew Dragon earlier this year, NASA has relied on Russian Soyuz spacecraft to shuttle its astronauts to orbit.
Demo-2 was considered a successful demonstration of Crew Dragon and NASA looks at Crew-1 as the first official crew rotation mission from US shores since the retirement of the Shuttle.
"It's exciting, especially with Crew-1 being the first time we've ever put four people on a space capsule ever, as humans, like that's pretty cool," explained NASA's Anthony Vareha, the lead flight director for the mission. "It's also the longest mission of a crewed US capsule ever."
Who are the astronauts flying in the Crew Dragon?
Along for the historic flight will be NASA's Crew Dragon Commander Michael Hopkins, pilot Victor Glover and mission specialist Shannon Walker, joined by Japan Aerospace Exploration Agency (JAXA) mission specialist Soichi Noguchi to the space station.
Up until now, three people in a Soyuz capsule amounted to a cramped ride, but Crew Dragon can accommodate up to seven (for comparison, the Space Shuttle flew crews of up to eight), making the trip for these four spacefarers seem relatively spacious.
How long is the trip?
The members of Crew-1 are embarking on a six-month science mission, which is exciting for people involved in the orbital and space science world because four crew members making the trip amounts to more hands available on the station to do more experiments in microgravity.
"It's going to be exciting to be able to see how much work we can get done while we're there," Hopkins said Monday.
But first, of course, the astronauts will have to get there. The actual trip to the ISS takes a little more than a full 24 hours from launch Saturday evening to docking with the station Sunday evening around 8 p.m. PT.
How do I watch?
Right here. NASA and SpaceX will stream the launch, currently set for Sunday, Nov. 15 at 4:27 p.m. PT (after being delayed from Saturday, due to weather) from Launch Complex 39A at the Kennedy Space Center.
NASA TV will broadcast the launch and the docking, and we're also carrying a livestream, which you can catch below.