Watch live: SpaceX's Crew Dragon spaceship is bringing 4 astronauts back to Earth, ending NASA's longest human spaceflight

• SpaceX's Crew-1 mission for NASA is flying four astronauts back to Earth overnight.
• The Crew Dragon spaceship must plummet at high speed, deploy parachutes, and land in the ocean early Sunday.
• Watch NASA's livestream below to see the astronauts fly aboard Crew Dragon and fall to Earth.

Update: Crew Dragon Resilience splashed down in the Gulf of Mexico early Sunday, safely delivering the Crew-1 astronauts back to Earth. Read more in our story.

A gumdrop-shaped fireball is set to plummet through the dark Florida skies overnight.

SpaceX's Crew Dragon spaceship, carrying four astronauts for NASA, is preparing to plow through the atmosphere at 25 times the speed of sound, deploy four parachutes as it approaches the coast of Florida, and then glide to a gentle splashdown in the ocean at about 2:57 a.m. ET on Sunday.

The return journey has already begun. The spaceship, named Resilience, has backed away from the International Space Station (ISS), carrying Shannon Walker, Victor Glover, and Mike Hopkins of NASA, along with Soichi Noguchi of the Japan Aerospace Exploration Agency.

Resilience carried these astronauts to the ISS in November. They have been living and working there ever since.

Their mission, called Crew-1, officially restored NASA's ability to launch people into space on a US spacecraft for the first time since the Space Shuttles stopped flying in 2011. Six-month spaceflights have been routine for NASA astronauts launching on Russian Soyuz spaceships, but until now, the US had never flown such long-term missions on its own.

Crew-1 is also SpaceX's first routine astronaut flight for NASA. The agency has already purchased five more Crew Dragon missions. The second one, Crew-2, launched four more astronauts toward the ISS on April 23; they reached the station the following morning.

Walker, Glover, Hopkins, and Noguchi greeted the new arrivals, but the ISS was getting crowded. So on Saturday evening, the Crew-1 team climbed back aboard the Crew Dragon Resilience for the journey home.

Watch live as Crew-1 returns to Earth

NASA is broadcasting the nearly seven-hour journey - including the fiery plunge to Earth and the splashdown at the end - via the livestream below, which began at 6 p.m. ET on Saturday.

Walker, Glover, Hopkins, and Noguchi boarded the Resilience capsule and closed its hatch behind them at 6:20 p.m. ET on Saturday. After about two hours of checkouts, the hooks keeping Resilience attached to the space station retracted at 8:35 p.m. ET, undocking the spaceship from the ISS. The vehicle then fired its thrusters to back away.

The Crew-1 return trip was originally scheduled for Wednesday, then for Saturday morning, but NASA delayed it twice after forecasts predicted high winds in the splashdown zones.

SpaceX has flown humans back to Earth from the ISS once before - on a crewed test flight called Demo-2. In May, that mission rocketed NASA astronauts Doug Hurley and Bob Behnken into orbit. They stayed on the ISS for two months before splashing down in the Gulf of Mexico.

The entire descent and landing process is automated, but Hurley advised the Crew-1 astronauts to make sure they're "staying ahead of the capsule," according to Hopkins, the mission commander.

"Preparing for that landing is just going over our procedures and making sure when we get into that sequence of events, that we're ready to go, and we're following right along with all of the automation as it takes us to, hopefully, a safe landing," Hopkins told reporters in a call from the ISS on Monday.

If all goes well, Resilience is expected to spend the next few hours orbiting Earth and maneuvering into position. At 10:58 p.m. ET, the capsule should jettison its trunk - a lower section outfitted with fuel tanks, solar panels, and other hardware - which it will no longer need.

From there, the Crew-1 astronauts could be in for a bumpy ride.

"The landing was - I would say it was more than what Doug and I expected," Behnken told reporters after he returned to Earth aboard the spaceship. "I personally was surprised at just how quickly events all transpired."

"It felt like we were inside of an animal," he added.

Behnken also said that pivotal moments of the landing process - such as when the capsule separated from its trunk and when the parachutes deployed - felt "very much like getting hit in the back of the chair with a baseball bat."

What to expect as the astronauts plummet to Earth

As the Resilience spacecraft approaches Earth, it is expected to fire its thrusters continuously, pushing itself further into the atmosphere.

Soon, the spaceship should be plummeting through the atmosphere, superheating the material around it to a blistering 3,500 degrees Fahrenheit. At that point in his flight, Behnken said, he could feel the capsule heating up, and the force of Earth's gravity pulling on him for the first time in two months. It felt like being in a centrifuge, he added.

The Crew Dragon's heat shield - a collection of heat-resistant tiles that line the spaceship's underbelly - must deflect that superheated material to protect the astronauts inside. After the Demo-2 landing, NASA and SpaceX found that one of those tiles had worn away more than expected. So SpaceX reinforced the heat shield with stronger materials.

Once it's about 18,000 feet above the ocean, Resilience should deploy four parachutes - which brings a "pretty significant jolt," Behnken said.

From there, Resilience should glide to a gentle splashdown in the ocean at 2:57 a.m. ET on Sunday. A recovery crew is expected to retrieve the charred capsule and carry the astronauts to shore.

During Behnken and Hurley's return to Earth, a crowd of onlooking boats got dangerously close to the spaceship after it splashed down. To prevent that from happening again, SpaceX, NASA, and the Coast Guard plan to secure a 10-mile no-boat perimeter around the Crew-1 splashdown site.

"Landings are always fairly dynamic, particularly with the capsules like this, particularly when the chutes are opening. So that's always a little bit exciting," Hopkins said.

When asked what he'd like to eat upon returning from the ISS, he replied, "If I have an appetite, that's going to be a bonus."

This post has been updated with new information. It was originally published on April 26, 2021.