In the wee morning hours of Saturday, SpaceX’s Falcon 9 rocket is scheduled to take to the skies over Florida, propelling a gumdrop-shaped spacecraft to the International Space Station. The rocket’s payload is SpaceX’s new Crew Dragon capsule — the company’s very first vehicle designed to carry people to space.

Though the capsule is meant for passengers, no one will be on board for this trip. That’s because this flight is, at heart, a test. The mission, called Demonstration-1 or DM-1, is meant to show NASA that the Crew Dragon is space-worthy and safe for future human crew members.

the very first people who will fly on the Crew Dragon will be NASA astronauts

NASA is particularly concerned about this, because the very first people who will fly on the Crew Dragon will be NASA astronauts. The Crew Dragon is a critical part of the space agency’s Commercial Crew Program, which revolves around using privately-made spacecraft to transport NASA astronauts to and from the International Space Station. Both SpaceX and fellow aerospace company Boeing have been crafting capsules for this purpose, and after five years of development, SpaceX could be the first one to put its vehicle in space. If all goes well, the next time it goes to orbit, the Crew Dragon could have people inside.

Here’s why DM-1 is happening, what to expect, and what comes next once the launch is over.

Why is this important?

When NASA’s Space Shuttle stopped flying in 2011, the space agency lost its main method of sending its astronauts to the International Space Station. So ever since then, NASA has been buying seats on board Russia’s Soyuz spacecraft in order to get US astronauts and international partners to the ISS. It’s an expensive arrangement, costing NASA $81 million per seat. It’s also NASA’s only option at the moment. If the Soyuz were to stop operating for an extended period of time, NASA would have no way to get its people to space.

That’s why, over the last decade, NASA has been working on a way to get its astronauts back on American-made vehicles again. Through the Commercial Crew Program, NASA gave contracts to both SpaceX and Boeing, valued at $2.6 billion and $4.2 billion respectively, in order to partially fund the development of new vehicles that could ferry astronauts to and from the ISS. Ever since, Boeing has been working on its vehicle, the CST-100 Starliner, while SpaceX has been developing the Crew Dragon.

Both vehicles are slated to fly this year, with Boeing aiming for its first test flight in April. It’s been a long and bumpy road to get to this point, though. When NASA first awarded SpaceX and Boeing their contracts in 2014, the goal was to fly the first astronauts by 2017. But numerous delays and technical hurdles have pushed back that target. NASA safety advisors raised concerns about certain aspects of the vehicles’ designs, while other experts questioned SpaceX’s plans for fueling its rockets with people on board.

Slowly but surely, those concerns are being resolved, and NASA is eager to see the Crew Dragon in action on this upcoming mission.

How will the launch work?

The launch will be similar to other missions SpaceX has flown to the International Space Station. The Crew Dragon is an upgraded version of the company’s Dragon cargo capsule, which SpaceX has used to send supplies to the astronauts living on the International Space Station since 2012. Just like those capsules, the Crew Dragon will launch to orbit mounted on top of one of SpaceX’s Falcon 9 rockets.

The vehicle will take off from SpaceX’s launchpad from NASA’s Kennedy Space Center in Cape Canaveral, Florida. In 2014, the company took over a launch site at Kennedy once used for missions of NASA’s Saturn V rocket to the Moon, as well as old Space Shuttle missions. SpaceX modified the pad to suit flights of the Falcon 9, and added other hardware needed to support future crewed missions. One such addition is a new tunnel, attached to a tower near the pad, that astronauts will eventually walk across to reach the spacecraft.

DM-1 will lift off at 2:49AM ET on Saturday, March 2nd. The very early launch time will let the capsule meet up with the International Space Station on its orbit. As of now, weather is looking pretty good for launch, with an 80 percent chance that conditions will be favorable.

What will happen on this mission?

NASA says that the Crew Dragon is equipped with various instruments and cameras designed to gather data throughout its flight. It’ll carry about 400 pounds of cargo and weigh similarly to future capsules when they have people on board. A test dummy is also going along for the ride inside the capsule, wearing the custom flight suit that SpaceX designed for future passengers.

Once Crew Dragon is in orbit, it will circle the Earth a few times before approaching the International Space Station about a day later. One of the key differences between this launch and a standard cargo mission involves its docking procedures. Up until now, all of SpaceX’s cargo flights have been berthed to the ISS, meaning the vehicles travel close to the station and are then grabbed by a robotic arm operated by an astronaut. The arm brings the capsules even closer to the station and then attaches them to a port.

The Crew Dragon doesn’t need a robotic arm to get to the International Space Station. It’s designed to automatically dock with the ISS all on its own, using a combination of software, lasers, and sensors. In 2016, astronauts installed a new docking adapter to the outside of the International Space Station, which will be the Crew Dragon’s target for this flight. If all goes well, Crew Dragon is set to dock with the ISS around 6AM ET on Sunday, March 3rd.

The hatch on the spacecraft will be opened and there’ll be a little welcoming ceremony

When it arrives, the hatch on the spacecraft will be opened and there’ll be a little welcoming ceremony with the three crew members on the ISS: NASA astronaut Anne McClain, Canadian astronaut David Saint-Jacques, and Russian cosmonaut Oleg Kononenko. The trio will also go inside to check it out and offload the cargo.

The capsule will stay attached to the ISS for less than a week, leaving five days later on Friday, March 8th. Crew Dragon will undock from the ISS super early, around 2:30AM ET, and then drift farther away from the station. After 7:30AM ET, the capsule will ignite its engine and take itself out of orbit, descending to Earth. A parachute system will deploy to lower the capsule down gently into the Atlantic Ocean around 8:45AM ET. NASA is hoping to get a good view of this parachute deployment, too, in order to qualify the system for future crewed flights.

What comes next?

Both NASA and SpaceX will spend time after DM-1 evaluating the flight. And in about a month, it’ll be time for SpaceX’s next big launch — one that will test out the company’s emergency escape system.

Know as the “in-flight abort,” this is a scenario that SpaceX would implement in case the Falcon 9 rocket experiences a problem during flight, creating a dangerous environment for the crew. Embedded in the structure of the Crew Dragon capsule are eight thrusters, called Super Dracos, which can ignite during launch and carry the vehicle away from a malfunctioning rocket.

SpaceX plans to test out this capability using the same Crew Dragon that launches this weekend. The company will launch the capsule from Florida and then send a command for the abort system to activate. The rocket will shut down during the test, while the Crew Dragon’s thrusters carry the capsule away. SpaceX CEO Elon Musk mentioned on Twitter there’s a “high probability of this particular rocket getting destroyed” during the test.

this weekend’s flight will be a big step toward putting people on a SpaceX vehicle

Once NASA is satisfied with the spacecraft’s safety procedures, SpaceX’s capsule will take to orbit with people on board, potentially as early as July. SpaceX’s first test crew includes two people, Bob Behnken and Doug Hurley, who are veteran fliers at NASA. During that trip, the two will dock with the ISS and spend a couple weeks up in orbit doing tests on the Crew Dragon vehicle. They’ll then depart and splash down in the Atlantic, where they’ll be met by one of SpaceX’s boats designed to retrieve the capsule.

If that mission goes well, then NASA will make the final decision on whether to certify SpaceX’s Crew Dragon for regular crewed missions to the International Space Station. There’s still quite a lot to do between now and then. But this weekend’s flight will be a big step toward putting people on a SpaceX vehicle.

Updated February 28th, 1:00PM ET: This article was updated to include the changed time for undocking at the ISS.