Boeing designed the CST-100 Starliner to fly up to seven passengers. NASA funded the work with a $4.2 billion contract.
The money comes from the Commercial Crew Program, which NASA started 2010. The goal: Have companies, not the US government, build new spaceships to reach the International Space Station.
NASA desperately needs those commercial spaceships because it retired its fleet of space shuttles in July 2011.
Ever since then, NASA has solely — and uncomfortably — relied on Russia to ferry US astronauts to and from orbit inside that nation's Soyuz spacecraft. A single round-trip ticket now costs NASA more than $80 million.
next slide will load in 15 secondsSkip AdSkip AdHelp is on the way, though. Out of a dozen companies, Boeing and SpaceX made it through NASA's competition with two independent spaceship designs.
Before Boeing's Starliner vehicle can fly astronauts, though, NASA requires a series of test flights and demonstrations.
NASA requires Starliner to fly astronauts to safety in the unlikely event of a rocket-launch failure. So Boeing developed new engines ...
... And tested them on a full escape system in November. The test showed Starliner can automatically blast away from impending disaster.
Though the engines initially leaked, and the parachutes took years to perfect — such a system hadn't been used since the Apollo program decades ago — Boeing eventually persevered.
next slide will load in 15 secondsSkip AdSkip AdThese and many other subsystems culminated in the first-ever orbital launch of a Starliner at 6:36 a.m. ET on December 20.
Nobody was inside except a mannequin named Rosie. There was also some food, Christmas presents, and other cargo for astronauts aboard the space station.
The spaceship rode toward space atop an Atlas V rocket, built by United Launch Alliance. It lifted off from Cape Canaveral, Florida.
To viewers of a NASA TV livestream, the flight seemed to be smoothly for more than half an hour.
The Starliner separated from the Atlas V after about 15 minutes.
next slide will load in 15 secondsSkip AdSkip AdBut mission control knew something was wrong shortly after that. About 31 minutes into the mission, Starliner was supposed to have automatically fired its engines to set a course for the space station — but it never did.
When the rocket disconnected from the Starliner, the ship's clock was 11 hours too far ahead. This caused the ship's autonomous navigation system to fire small reaction-control thrusters and adjust its position in space —for a phase of the mission it had not yet reached.
And possibly because Starliner wasn't in the right position, it had trouble connecting with NASA satellites: Mission Control couldn't immediately override the autonomous system and tell the ship to fire its main engines for orbit.
As a result, the Starliner burned through about 25% of its fuel before Mission Control finally took remote-control of the ship. There wasn't enough fuel to reach the space station — only rescue the ship into a stable orbit and prevent it from crashing to Earth.
It was a tense moment for everyone on the mission, though officials said human pilots could have made a big difference. "Had we had an astronaut on board, we very well may be at the International Space Station right now," Bridenstine said on Sunday.
next slide will load in 15 secondsSkip AdSkip AdThat's because — according to NASA managers, Boeing officials, and astronauts themselves — a person would have seen the ship had missed a critical engine burn.
At that point, someone would have used Starliner's manual controls to bypass the autopilot and take over the flight.
So while the Starliner never reached its target destination, Christmas presents and all, and did not dock with the ISS ...
... Everyone was happy the spaceship was saved.
"I'd like to express Boeing's regrets to the ISS crew to whom we did not bring the Christmas presents," Boeing's Chilton said. "That's not cool. We own it."
next slide will load in 15 secondsSkip AdSkip AdStarliner ended up orbiting Earth for about two days instead of a week. Along the way, Boeing tested out as many systems as possible. Chilton said on Sunday that the mission probably achieved about 85-90% of its objectives for NASA.
Early Sunday morning, the Starliner shed its service module and orbital thrusters.
This allowed the space capsule to turn its heat shield toward Earth's atmosphere, absorb and deflect the heat of reentry, and safely return to the planet.
The capsule deployed its parachutes over NASA's White Sands Test Facility in New Mexico, popped off its heat shield ...
... And blew up impact-absorbing airbags before landing in the desert.
next slide will load in 15 secondsSkip AdSkip AdThe space capsule landed gently on the sandy turf just before dawn on Sunday.
Ground crews made of Boeing, NASA, and US Army personnel had trained for months for this moment and were ready to recover the ship.
And because the ship landed right where it was supposed to, the recovery team reached the Starliner in minutes.
"When we look at how the launch vehicle, the Atlas V and Starliner, perform, it's an incredibly good design. We didn't see any major problems," Steve Stich, the deputy manager of NASA's Commercial Crew Program, said during Sunday's press briefing.
Recovery of the Starliner capsule is crucial: Boeing plans to launch and reuse it many times with refurbishment.
next slide will load in 15 secondsSkip AdSkip AdThe Starliner that launched over the weekend won't be the first to fly people. But its supposed to be refurbished and fly NASA astronauts Suni Williams and Josh Cassada, perhaps sometime next year.
Williams named the recovered Starliner spaceship "Calypso" after the ship of famed explorer Jacques Cousteau.
NASA wouldn't say if Boeing needs to repeat an uncrewed Starliner mission or proceed to first-ever mission with astronauts. Bridenstine would only say it could take months to review all of the mission's data and arrive at a decision.
Whatever the case, and perhaps even at a major cost to Boeing, Chilton said the company would do whatever it takes to fly astronauts — including another uncrewed test. "We're in. Simple as that," he said during a teleconference on Saturday.
NASA says there is no race to resurrect human spaceflight capabilities in the US, but SpaceX could be the very first to fly astronauts.
next slide will load in 15 secondsSkip AdSkip AdSpaceX's Crew Dragon already completed its orbital flight and docking test, called Demo-1. That space capsule later exploded during a test, though.
Despite the setback, SpaceX has made up for lost time, completed the same test, and is planning a launch-abort test in January. After that, NASA may decide SpaceX is ready to launch astronauts as soon as Spring 2020.
Both companies may ultimately fly astronauts, giving NASA two ways, as Bridenstine often likes to say, to fly American astronauts from American soil on American rockets for the first time in nearly a decade.