It’s been nearly 10 years since NASA astronauts launched from U.S. soil — a long, ignominious streak that’s been compounded by delays and technical challenges.

But finally, the space agency on Friday set the date for when it will fly its astronauts from the Florida Space Coast again: May 27.

While the date could change — in spaceflight they often do — the announcement marks a significant milestone in NASA’s winding, at times tortuous, journey to regain its human-spaceflight wings since it retired the space shuttle in 2011.

Space shuttle Atlantis’s liftoff on July 8, 2011, marked the end of the space shuttle era after 135 missions. (The Washington Post)

This time, though, the launch will be markedly different from any other in the history of the space agency. Unlike Mercury, Gemini, Apollo or the space shuttle era, the rocket will be owned and operated not by NASA, but by a private company — SpaceX, the hard-charging commercial space company founded by Elon Musk.

For all the company’s triumphs, and its experience flying cargo to the International Space Station for NASA, it has never flown a human into space, a significant and dangerous challenge. NASA has spent years working with the California-based company to ensure its Falcon 9 rocket and Dragon spacecraft can safely deliver astronauts to orbit. And the flight would be the culmination of years of work, which has at times seen setbacks and delays.

With a successful launch, SpaceX would accomplish an upset over its rival, Boeing, which also is under contract to fly NASA crews to the space station as part of the agency’s “commercial crew program.” Boeing’s Starliner spacecraft suffered significant setbacks during a test flight without astronauts in December that prevented it from docking with the station and prompted an investigation by NASA.

That investigation uncovered numerous flaws, and Boeing recently agreed to refly the mission without astronauts on board before proceeding to a crewed flight. With the reflight to be likely toward the end of this year, a crewed Boeing flight is thought unlikely until next year. The company, reeling from the 737 Max crisis and the corornavirus pandemic, has set aside $410 million to pay for the costs of the investigation and the additional test flight.

In 2014, NASA awarded a total of $6.8 billion in contracts to SpaceX and Boeing, which won the larger share of the pot, $4.2 billion, while SpaceX got $2.6 billion for the same work. Last year, SpaceX successfully flew its Dragon to the station, paving the way for a crewed flight.

In an interview with The Washington Post last week, NASA Administrator Jim Bridenstine said the agency needed to push on with the launch, despite the coronavirus pandemic, to maintain an American presence on the space station, which has been continuously occupied for 20 years.

The space station represents “a $100 billion investment by the American taxpayer,” he said. “It’s a symbol of diplomacy and cooperation that is important not just for our country but the whole world. It’s mission essential."

A successful flight would propel SpaceX into rare company, with the United States, Russia and China the only countries who have flown humans to orbit. And it would end NASA’s dependence on Russia to fly its astronauts.

Once NASA retired the space shuttle and lost the ability to fly humans, it became dependent on Russia to launch its missions. And Russia began raising the prices it charged for the service — from $21.3 million a seat in 2006 to almost $82 million a seat by 2015, an increase of nearly 300 percent.

On Twitter Friday, Musk said SpaceX, which he founded in 2002 with the ultimate goal of sending humans to Mars, has made “good progress, but 18 years to launch our first humans is a long time. Technology must advance faster or there will be no city on the red planet in our lifetime.”

For the upcoming SpaceX mission, NASA has assigned two of its most experienced astronauts: Bob Behnken and Doug Hurley. Both are married to astronauts. Both have been to space multiple times. Both are former military test pilots.

If all goes to plan, they’ll lift off at 4:32 p.m. from the Kennedy Space Center’s pad 39A, the historic starting point for many Apollo and shuttle missions. Hurley’s presence would mark a bookending for NASA, since he was on the last shuttle mission, which lifted off from 39A in 2011.

SpaceX’s launch comes at an important time for NASA, which has been scrambling to ensure that it keeps a presence on the International Space Station. On Friday, NASA astronauts Jessica Meir and Drew Morgan returned to Earth, leaving Chris Cassidy as the lone American on the station with two Russian cosmonauts.

The Washington Post's Christian Davenport spoke to astronauts on the International Space Station to hear how they cope with living together in a small space. (The Washington Post)

It’s unclear how long Behnken and Hurley will remain aboard the station. Initially, their mission was expected to be a short stay. But because of the setbacks and delays, suffered by both SpaceX and Boeing, their mission will be extended.

NASA said that the Dragon spacecraft can remain in orbit for 110 days and noted that the “specific mission duration will be determined once on station based on the readiness of the next commercial crew launch.”