The space shuttle Atlantis rolled to a stop on a runway at NASA’s Kennedy Space Center in Florida on July 21, 2011, its last flight. That ended an era of American spacecraft carrying astronauts to space.

“Mission complete, Houston,” said Christopher Ferguson, the mission commander. “After serving the world for over 30 years, the space shuttle has earned its place in history, and it’s come to a final stop.”

Nearly eight years later, a replacement for the space shuttles is finally on the launchpad, not far from where Atlantis landed. During that time, NASA astronauts have flown to the International Space Station aboard Russian Soyuz spacecraft.

Reflecting a new reliance on the private sector, NASA hired two companies, SpaceX and Boeing, to design and build transportation for its astronauts.

After years of delays, the first of those systems — SpaceX’s Crew Dragon capsule — is scheduled for liftoff Saturday at 2:49 a.m. Eastern Standard Time on top of one of the company’s Falcon 9 rockets. Forecasts call for an 80 percent chance of favorable weather.

“This is an invaluable exercise for us to learn in the space environment how these systems will be working,” said Kathryn Lueders, manager of NASA’s Commercial Crew program, during a news conference Thursday.

The capsule is not yet ready for astronauts, but the flight is intended as an end-to-end test, doing everything that one with astronauts would do, including docking with the International Space Station early Sunday. Then on March 8, it is to leave the space station and parachute into the Atlantic Ocean a few hours later.

During a news conference last week, William Gerstenmaier, the NASA official who oversees the human spaceflight program, said problems were to be expected.

“I guarantee everything will not work exactly right, and that’s cool,” Gerstenmaier said. “That’s exactly what we want to do. We want to maximize our learning so we can get this stuff ready so when we put crew on, we’re ready to go do a real crew mission, and it’ll be the right safety for our crews.”

A subsequent flight with people aboard could come later this year. Boeing’s first test flight for its capsule, named Starliner, could be launched as soon as next month.

The Crew Dragon is an upgraded, sleeker version of the SpaceX Dragon capsule that has been taking cargo to the space station since 2012.

Crew Dragon’s powerful thrusters serve as part of the escape system to power astronauts to safety in case of a problem with the rocket. It also has the ability to autonomously dock with the space station, instead of relying on an astronaut aboard the station to grab and guide the capsule with the station’s robotic arm.

The SpaceX capsule also includes up to seven seats and consoles displaying information for the astronauts. For this flight, one of the seats will be occupied with a sort of artificial person — what NASA calls an ATD or “anthropomorphic test device” — which will be wearing a SpaceX spacesuit. The device includes sensors to measure forces and accelerations that a person would experience on the trip.

The SpaceX engineers named it Ripley, after the heroine in the Alien movies played by Sigourney Weaver.

Similar to how SpaceX broadcast video of a spacesuit-clad “Starman” in a Tesla roadster launched by its Falcon Heavy rocket last year, there will be cameras inside the Crew Dragon capsule. “It will give you a perspective that you would have if you were inside,” said Hans Koenigsmann, SpaceX’s vice president for build and flight reliability.

SpaceX has faced scrutiny for decisions like planning for the crew to be onboard while the rocket is fueled. In the past, NASA has considered that too risky, but SpaceX prefers to use supercooled liquid oxygen and kerosene, which are more efficient but cannot remain at those temperatures for very long. Fueling begins just 35 minutes before liftoff.

The space agency has tentatively approved SpaceX’s approach, known as “load and go.” “We came to the conclusion that this was an acceptable risk that we were willing to take,” said Patrick Forrester, chief of NASA’s astronaut office.

Other issues still to be resolved before a crewed flight include certification of the parachutes and fixing a design issue with the thrusters where pieces can break off if they get too cold.

Russia, the main partner on the International Space Station, also raised concerns that the Crew Dragon did not have a backup system to steer the capsule away if the main computer were to fail. But on Thursday, NASA officials said they had managed to allay those worries by adding precautionary measures.

If there are additional delays, NASA may buy more Soyuz seats from the Russians.

When the Obama administration announced the beginnings of the commercial crew program in 2009, NASA already had plans to develop a much more expensive rocket, the Ares I, as part of a project to send astronauts back to the moon. But the NASA rockets, and the moon program, were canceled.

The Trump administration is again interested in the moon, but is keeping the commercial approach.

By themselves, the Boeing and SpaceX spacecraft do not push NASA any farther out into the solar systems; both are designed only to go to low-Earth orbit, the same trip that the Soyuz has been making for decades.

The hope that commercial rides to space could spur a new space industry has also not yet materialized. However, NASA appears to be applying a similar approach to new programs, including a call to private companies to develop spacecraft to take astronauts to the surface of the moon. That could lead to unexpected outcomes in the space business.

“I think we’re at a Wright brothers moment for commercial space,” Phil Larson, who served as a space adviser in the Obama White House and is now an assistant dean at the University of Colorado’s College of Engineering and Applied Science, said in an interview. “We’ll have a new fleet of American spacecraft. Anything is possible, and I think markets will show up.”

This article originally appeared in The New York Times.