The Canadarm 2 reaches out to capture the SpaceX Dragon cargo spacecraft and prepare it to be pulled into its port on the International Space Station on April. The (AP Photo/NASA)

The nation's space agency selected three commercial companies for the next round of missions to resupply the International Space Station, giving a vote of confidence to incumbents SpaceX and Orbital ATK and choosing a new player, Sierra Nevada Corp.

NASA's highly-anticipated announcement follows some historic highs and devastating lows in the booming commercial space industry, and it expands the field of companies handling the unmanned missions through 2024.

Unlike SpaceX of Hawthorne, Calif. and Dulles-based Orbital, which use capsules to deliver cargo, Sierra Nevada has built an entirely different spacecraft called the Dream Chaser, a sort of miniature space shuttle that can land on runways like a commercial airplane.

NASA chose the companies for a minimum of six missions each as part of a total contract that could reach $14 billion. While NASA has not yet ordered any missions, officials said the contracts would give the agency the flexibility to make the most of the International Space Station’s potential as a platform for scientific research.

“This will ensure that we can keep the [International Space Station] fully stocked for crew… to fully utilize the ISS as a laboratory,” said Kirk Shireman, NASA’s International Space Station program manager.

The missions are expected to begin in late 2019.

NASA’s decision to hire commercial enterprises came after years of relying on the space shuttle, which was retired in 2011. Some were skeptical of the shift but the agency argued the private sector was fully capable of delivering food, water, science experiments and more to the orbiting lab 220 miles above Earth.

In 2014, NASA awarded additional contracts, worth up to $6.8 billion combined, to SpaceX and Boeing to fly astronauts to the station. Since the shuttle retired, the United States has been paying the Russians to fly its astronauts to the station in a pricey arrangement that now costs about $80 million per seat.

Elon Musk's SpaceX and Boeing have been developing their manned spacecraft and the first flights are scheduled as early as next year.

Contracting out the space station work allows NASA to focus on other missions, particularly deep space exploration, the agency has said. But NASA and the industry were jolted by some high-profile disasters. In late 2014, Orbital ATK, then known as Orbital Sciences, had its rocket blow up, incinerating the supplies destined for the space station. The explosion of the Antares rocket caused $15 million in damage to the launch pad at Wallops Island, Virginia, including a 50 to 60 foot crater.

Then about eight months later, SpaceX’s Falcon 9 rocket blew up a couple minutes into flight, destroying yet another delivery to the station, and calling into question the ability of the commercial sector to deliver.

Both companies vowed to fix the problems and return to flight. And in December, they both had successful launches that restored confidence in their efforts.

Flying with an Atlas V rocket contracted from the United Launch Alliance, Orbital ATK’s Cygnus spacecraft successfully resupplied the station. Then, just before Christmas, SpaceX launched commercial satellites into space, and also pulled off the landing and safe return of its first stage at Cape Canaveral, potentially allowing it to be re-used.

[Elon Musk's SpaceX returns to flight and pulls off dramatic, historic landing.]

Since the Obama administration moved to contract out the space station missions, commercial companies have flown 35,000 pounds of cargo there, NASA Administrator Charles Bolden wrote in a blog post Thursday.

“Despite critics who may have said this was a pipe dream just five short years ago, we continue to transform the way NASA does business and as a result, today we’re able to mark another significant milestone that will carry President Obama’s vision further into the future,” he wrote.

He added that the agency is “firmly on track to return launches of American astronauts to the [International Space Station] from American soil on American commercial carriers.”

Orbital ATK said it has delivered 16,000 pounds of cargo since 2013.

“We are grateful for NASA’s continued confidence in our ability to provide reliable and affordable commercial cargo transportation services to the International Space Station,” said David W. Thompson, Orbital ATK’s president and chief executive, in a statement.

Sierra Nevada is a more than 3,000-person outfit headquartered in Nevada that was one of three finalists competing to fly astronauts to the space station, known as the commercial crew program, only to be edged out by Boeing and SpaceX.

Mark Sirangelo, the director of the company's space program called the loss of the commercial crew contract the company's Apollo 13 moment. The company was down, but not out and would find a way to survive by transforming its Dream Chaser vehicle, initially designed to fly astronauts, so that it could carry cargo as well. But there wasn't much time to submit a bid, due in December 2014, for the first commercial resupply contracts.

They worked through Thanksgiving, cramming at least six months of work into three. Members of the team decided that “we’ve come too far,” Sirangelo said in an interview at the time. “We believe in this product and our effort too much. It’s going to be hell for three months, but we’re going to do everything we can.”

On Thursday that paid off.

“Within a few short years, the world will once again see a United States winged vehicle launch and return from space to a runway landing," Sirangelo said in a statement following the announcement.