On the afternoon of May 27th, SpaceX is slated to launch its very first passengers to space, potentially heralding a new era of human spaceflight for the United States. It’ll be the first time in nearly a decade that people have launched to orbit from American soil, and it’ll be the first time that a private vehicle takes them there.

This historic flight is really a test. It’s the last big milestone for SpaceX as part of NASA’s Commercial Crew Program. The experimental initiative tasked private companies with creating new spacecraft for NASA that are capable of transporting astronauts to and from the International Space Station. SpaceX’s contribution to the program is a sleek, gumdrop-shaped capsule called the Crew Dragon. While it’s flown a few times before, the capsule has yet to carry people to space.

SpaceX spent the last six years getting to this point. Last year, the company did a full dress rehearsal, successfully launching the Crew Dragon to the station without a crew on board. The company also tested the capsule’s emergency escape system, confirming that the Crew Dragon can carry people to safety if something goes wrong during the launch. But there have been setbacks to overcome, too, including rocket failures and the explosion of a Crew Dragon capsule during a ground test last year. SpaceX has since recovered, referring to the failures as “gifts” that helped the company create a safer vehicle.

Now, it’s time for the Crew Dragon to have a crew. The vehicle’s first two passengers are veteran NASA astronauts Bob Behnken and Doug Hurley, who were assigned to this mission in 2018. After two years of training for this flight with both NASA and SpaceX, they’re ready to don SpaceX’s custom space suits and take their seats inside the capsule.

Here’s why this flight is so important, what to expect from the mission, and what it means for NASA and SpaceX moving forward.

The Importance

July 8th, 2011, marked the final flight of NASA’s Space Shuttle and the last time astronauts launched to orbit from the United States. Ever since, NASA has flown all of its astronauts and international partners to the space station on Russia’s Soyuz capsule. The arrangement costs NASA about $80 million per seat — and it has been the agency’s only option for getting people to the station.

Artistic renderings of SpaceX’s Crew Dragon (L) and Boeing’s CST-100 Starliner (R).
Image: Alex Parkin / SpaceX / Boeing

To end its reliance on another country, NASA worked with private industry to bring human spaceflight back to the United States. With the Commercial Crew Program, NASA awarded two companies — SpaceX and Boeing — contracts to develop their own vehicles that could ferry NASA’s astronauts to the space station and back. NASA paid SpaceX $3.14 billion to develop and fly the Crew Dragon, while Boeing received $4.8 billion to develop and fly the CST-100 Starliner.

An intense rivalry formed between the two companies over the years. Both experienced numerous technical delays and setbacks along the way, but ultimately, SpaceX pulled ahead. When it flies, SpaceX will become the first private company ever to fly humans to orbit.

The Launch

SpaceX’s Falcon 9 rocket will take off from the company’s launch site at NASA’s Kennedy Space Center in Cape Canaveral, Florida. Known as Launch Complex 39A, it’s seen launches of the Space Shuttle as well as Saturn V rockets that sent humans to the Moon. SpaceX started leasing the complex from NASA in 2014 and transformed the launchpad to support flights of the company’s Falcon 9 and Falcon Heavy rockets.

Hurley (R) and Behnken (L) outside of the Tesla that will take them to the launchpad.
Photo by Bill Ingalls / NASA

Suited up in SpaceX’s custom pressure suits, astronauts Behnken and Hurley will start making their way to the launchpad at around 1PM ET. To really make this an Elon Musk affair, the two astronauts will ride to the site in a white Tesla Model X, adorned with various NASA logos for absolute synergy. Once at the pad, the duo will take an elevator up near the top of the Falcon 9 rocket and walk across a suspended hallway known as the “crew access arm” to the entrance of the Crew Dragon.

Behnken and Hurley will climb inside the capsule and shut the hatch, which will mean it’s time to start fueling the vehicle. This part of the process has been fairly controversial for some in the aerospace community. Back when the Space Shuttle was flying, fueling occurred before astronauts boarded, since loading combustible materials into a spacecraft is considered risky. However, SpaceX opts to do fueling about half an hour before launch, after the crew is already on board. The company uses incredibly cold propellants to fly its Falcon 9, which boost the vehicle’s performance. The sooner SpaceX pumps in that propellant before launch, the less time there is for the liquids to warm up and boil away.

The crew access arm leading to the Crew Dragon, perched atop the Falcon 9.
Image: SpaceX

After years of debate over this procedure — called “load and go” — NASA finally signed off when SpaceX demonstrated it could be safely done on numerous flights.

Once all the propellant is loaded in the rocket, things will happen quickly. SpaceX will give the go-ahead to launch, with liftoff scheduled for 4:33PM ET. The company must launch at that exact time or be forced to delay to the backup launch date, which is currently set for Saturday, May 30th.

The Docking

If all goes as planned, it’s a quick trip to Earth orbit for the two astronauts. The Falcon 9 rocket will release the Crew Dragon into low Earth orbit about 12 minutes after takeoff. The rocket will then return to Earth where it is scheduled to land on a drone ship in the Atlantic Ocean.

For the next 19 hours, the astronauts will orbit the planet. During that time, the Crew Dragon will raise its orbit slightly by periodically igniting its engines, in order to catch up with the International Space Station. Inside the capsule, Behnken and Hurley will try to get some sleep — and perhaps use the capsule’s onboard toilet if nature calls.

SpaceX’s Crew Dragon approaching the International Space Station during its first test flight in 2019.
Image: NASA

The Crew Dragon is designed to require minimal input from its passengers, but since this is a test, Hurley and Behnken will do some manual flying before they reach the space station. “It’s obviously something that we want to make sure we understand completely for future crews in case they ever have to fly the vehicle manually,” Hurley said during a press conference. The plan is for Hurley to take control right after Crew Dragon reaches orbit as well as when they approach the space station.

But really, this is a time for the Crew Dragon’s autonomous docking system to shine. It’s a feature that the previous cargo version of SpaceX’s Dragon lacked when carrying supplies to the ISS. During those cargo missions, an astronaut on board the space station used a robotic arm to grab hold of an approaching Dragon capsule and draw it close to the ISS. Now, with the upgraded Crew Dragon, the capsule shouldn’t need any help from humans. Once Hurley is done flying manually near the station, the Crew Dragon’s automatic system will kick in. Using a series of sensors and cameras, the capsule will fly itself toward the ISS and hook itself onto an open docking port.

If the launch proceeds as planned, docking should take place at 11:29AM ET on Thursday, May 28th.

The Return

Once the Crew Dragon’s hatch is opened, Behnken and Hurley will join NASA astronaut Chris Cassidy and Russian cosmonauts Anatoly Ivanishin and Ivan Vagner on the ISS. Hurley said Cassidy recently sent them an email about their impending reunion in space. “He said something about he’s looking forward to seeing our ugly mugs onboard space station,” Hurley recalled.

Originally, NASA planned to keep the astronauts at the space station for only a few weeks. But plans changed as delays in the Commercial Crew Program prolonged the development of SpaceX and Boeing’s vehicles. The first crewed flights were supposed to take place in 2017, and with the expectation that these vehicles would be regularly flying by now, NASA purchased a limited number of seats on Russia’s Soyuz rocket. Those seats started to run out, and now Cassidy is tasked with all American-led operations on the space station.

About six months ago, NASA decided to extend Behnken and Hurley’s stay on board in order to maintain a bigger crew on the ISS. Now it seems likely they’ll be up in space for a few months, though NASA hasn’t decided yet when the astronauts will return. The Crew Dragon can only stay in space for about four months because of its solar panels. The thin atmosphere in space degrades the panels over time, limiting the vehicle’s lifetime in orbit.

The four parachutes of the Crew Dragon, lowering the vehicle into the ocean during its flight test in 2019.
Image: NASA

NASA says it will make the decision about the crew’s return date while they’re in space. As an added bit of insurance, NASA recently purchased one more seat on a Soyuz flight for this fall in case of further delays with the Commercial Crew vehicles.

When the time comes, Behnken and Hurley will climb back into their Crew Dragon, close the hatch, and detach from the space station. They’ll distance themselves from the ISS and then eventually take the plunge through Earth’s atmosphere. A suite of four parachutes will lower them down, allowing them to splash safely in the Atlantic Ocean off the Florida coast.

The Unthinkable

SpaceX has spent years doing tests and inspections to ensure that this launch performs safely. But this launch is a test, and the specter of failure weighs heavily on many minds. If something goes awry, a built-in emergency escape system will provide an extra layer of protection for the astronauts.

Embedded inside the outer walls of the Crew Dragon are tiny thrusters called SuperDraco engines. These thrusters are designed to ignite during flight in case something goes catastrophically wrong. The SuperDracos can carry the Crew Dragon up and away from a malfunctioning rocket, and once far enough away, the capsule’s parachutes can deploy, lowering the vehicle down into the Atlantic Ocean.

It’s a maneuver that’s only needed in the case of an emergency, but SpaceX claims this option is available during every point in the flight, until the Crew Dragon is deployed into orbit. And that actually means NASA and SpaceX are fairly limited about when this mission can launch. An abort could bring the Crew Dragon down in an extremely wide area of ocean in the Atlantic, and NASA wants to make sure that the weather is good in every possible location the capsule could touch down.

“We’re actually looking at waves — we’re looking at wave velocity and wave height — because we need to make sure that if the crew has to come down in a launch escape scenario, that they would come down in a sea state that would keep them safe and the rescue forces would be able to come and get them,” Benji Reed, director of crew mission management at SpaceX, said during a press conference. SpaceX will be considering the weather in more than 50 locations all the way up the East Coast to Canada and even across the Atlantic to Northern Ireland. That means weather delays are more likely than not.

The weather has been looking spotty for launch on May 27th so far, but today, the 45th Space Wing in Florida predicted a 60 percent chance that conditions will be favorable for launch.

The Future

Once Behnken and Hurley are back on Earth with their families, it’s time to start making these kinds of trips routine — which is what the Commercial Crew Program is all about. SpaceX and NASA will pore over the data gathered during this test flight and use that information to certify the Crew Dragon for regular flights to and from the ISS.

SpaceX’s next, fully operational mission of the Crew Dragon will then just be a few months away. That flight will carry a crew of four: NASA astronauts Victor Glover, Mike Hopkins, and Shannon Walker, as well as Japanese astronaut Soichi Noguchi. Their flight is expected to occur in early fall, cementing a new age where commercial companies are routinely taxiing people to NASA’s space station.