SpaceX's Resilience spaceship autonomously docked to the space station with 4 astronauts inside, kicking off a historic mission for NASA

• SpaceX on Sunday launched its first operational mission into orbit for NASA, with four astronauts on board.
• On Monday night, the astronauts caught up to International Space Station and docked.
• The mission, named Crew-1, calls for the astronauts to spend the next six months at the ISS — the longest human spaceflight launched from US soil.
• The commercial mission represents a major opportunity for NASA to boost the amount of scientific research it can perform on the ISS and sets the stage for future flights of private astronauts.

On Monday night, four astronauts arrived at the International Space Station inside SpaceX's Crew Dragon spaceship, teeing up what could be a record-breaking stay in orbit.

The NASA-funded commercial mission, called Crew-1, marks the first "operational" human spaceflight by SpaceX, the rocket company Elon Musk founded in 2002. It follows the Demo-2 mission, SpaceX's first launch of people, which lifted off in May and returned to Earth in August.

The astronauts of Crew-1 — Victor Glover, Mike Hopkins, and Shannon Walker of NASA and Soichi Noguchi of the Japan Aerospace Exploration Agency — lifted off from Kennedy Space Center in Florida on Sunday night atop a Falcon 9 rocket. The astronauts spent most of the night settling into Resilience, as they named their space capsule, while helping SpaceX troubleshoot propellant and cabin-heaters issues.

On Monday, the vehicle fired its thrusters several times to catch the ISS, beginning a rendezvous with the football-field-size laboratory at about 9 p.m. ET. Resilience spent an hour maneuvering about 400 meters in front of the facility and then another hour carefully — and automatically — inching forward while the astronauts looked over flight data.

"They won't have to push any buttons or fire any thrusters," Leah Cheshier, a NASA communications specialist, said during a live broadcast Monday night. "Dragon is doing this all on its own — it's completely autonomous."

The ship gently bumped into and engaged a temporary locking mechanism at 11:01 p.m. ET, softly anchoring the astronauts to their new home.

"Resilience, SpaceX. Docking sequence is complete. Welcome to the ISS," a SpaceX mission controller told the crew as grapple hooks tightly secured the vehicle onto a port at about 11:13 p.m. ET.

"Excellent job, right down the center," responded Hopkins, the mission's commander. "SpaceX and NASA, congratulations: This is a new era of operational flights to the International Space Station from the Florida coast."

'It was an amazing ride'

After a two-hour process of pressurizing an adapter with air, checking for leaks, and opening all the hatches, the crew finally floated onto the ISS at 1:02 a.m. ET.

The NASA astronaut Kate Rubins and the cosmonauts Sergey Ryzhikov and Sergey Kud-Sverchkov greeted them with open arms.

"It was an amazing ride," Hopkins said. "I can't tell you how excited we were when the rocket lifted off the pad, and the last 27 hours [in orbit] has gone really smooth actually."

The spaceship seemed to perform just as NASA and SpaceX hoped it would, once they resolved the early hiccups with the capsule's heaters.

"After clearing a couple alarms a little bit after launch yesterday, the vehicle arrived at the station today with full redundancy, full functionality, no issues whatsoever," Ven Feng, the deputy manager of NASA's Commercial Crew Program, which funded the spaceship's development, said in a press briefing after the docking. "Dragon's in beautiful shape."

Resilience and its passengers aim to spend the next six months in space. Assuming all goes well, Crew-1 is set to become the longest human spaceflight launched from US soil, beating a record set more than 45 years ago.

By expanding the ISS crew, those aboard won't have to spend so much of their time on maintenance, which will enable NASA to conduct more scientific research than before.

"I can't tell you how great it was to see you all come across the hatch," Kathy Lueders, NASA's associate administrator for human exploration and operations, told the crew members once they were on the ISS. "We're expecting a lot from you, a lot of good work up there."

A commercial boost to the space station after 20 years in orbit

Since the US retired its space shuttles in 2011, NASA has had to buy seats on Russia's Soyuz spaceships to get astronauts to and from the ISS — a facility that's been inhabited by humans continuously for 20 years.

To help close the gap, NASA launched the Commercial Crew Program a decade ago: a competition to spur private companies to develop new spaceships. The roughly $8 billion program led SpaceX to develop Crew Dragon and Boeing to develop its CST-100 Starliner (which may fly its first crew in late 2021).

NASA funded the Crew Dragon's creation with about $3 billion, and engineers at SpaceX designed, built, and tested it to exacting government requirements. Agency heads finally certified the system for regular flight last week — in large part because of the success of the Demo-2 flight, which carried the NASA astronauts Bob Behnken and Doug Hurley to and from the space station.

"This is the culmination of years of work and effort from a lot of people, and a lot of time, and we have built I think what I would call is one of the safest ... launch vehicles and spacecraft ever," Benji Reed, SpaceX's director of crew mission management, said during a press briefing before Crew-1's launch.

Crew-1 is the first of six round trips that NASA has purchased from SpaceX, and it formally kicks off an era of commercial spaceflight. The vehicle isn't limited to professional astronauts: Private astronauts may also fly to space in the coming years.

For example, Tom Cruise and the director Doug Liman are planning to launch to the ISS in 2021 aboard a Crew Dragon spaceship to film a movie. "Space Hero," a reality-TV show, is also angling to fly a contestant to the facility in 2023. A company called Axiom Space plans to contract SpaceX for the tickets.

The most important thing to NASA, though, is expanding the crew of the space station. The ISS offers an unparalleled zero-gravity environment in which to perform research that can't be conducted on Earth. Science is hard to get done when only a few crew members are on the ISS, however, since they're often preoccupied with regular cleaning and maintenance. Occasionally, their time also gets taken up hunting for leaks and fixing toilets.

Now, with SpaceX looking to maintain a continuous presence in orbit with Crew Dragon, the space station can be fully staffed — and NASA can make good on its $100 billion investment in the facility.

Crew-1 aims to power a variety of research, including studying how the body responds to eating certain foods in microgravity and spaceflight's effects on astronaut brains. The crew will also experiment with tissue chips, plant growing, and even part of a new spacesuit designed for the moon and Mars.

"We are ready for the six months of work that is waiting for us on board the International Space Station, and we are ready for the return," Hopkins said during a preflight briefing.