Why SpaceX's astronaut mission for NASA is such a big deal for Elon Musk's rocket company and the US as a whole

• SpaceX launched NASA astronauts to the International Space Station for the first time on May 30. Now it's poised to bring them home.
• The launch kicked off the first-ever human flight in a commercial spacecraft, and marked the first time an American-made vehicle has launched humans from US soil in nearly a decade.
• If successful, the mission could resurrect the US's human spaceflight capabilities and open a new era of commercial space exploration.

NASA and SpaceX are in the middle of making spaceflight history.

On May 30, Elon Musk's rocket company launched its first astronauts — Bob Behnken and Doug Hurley — under NASA's oversight (and with its funding). The next day, its Crew Dragon spaceship delivered Behnken and Hurley to the International Space Station.

Before that, the United States hadn't launched humans into space from American soil since 2011, when the last space shuttle made its final voyage into orbit.

For the nine years in between, NASA relied on Russian Soyuz rockets to ferry its astronauts to and from the space station. But that has become increasingly expensive and limited US access to the $150 billion orbiting laboratory.

Reliance on a single launch system has also raised a larger problem for any country looking to put astronauts into orbit: When Soyuz systems have issues — like a mysterious leak or a rocket failure that forces an emergency landing — space agencies have had nowhere else to turn.

That could all be about to change. If weather, hardware, and other factors cooperate, the Crew Dragon will complete its test mission, called Demo-2, on Sunday and bring Behnken and Hurley back to Earth.

Success would resurrect the US's ability to launch people into space. It would also mark SpaceX's first mission with passengers in the company's 18-year history.

"This is the culmination of a dream," SpaceX CEO Elon Musk told "CBS This Morning" ahead of the mission's launch in May. "This is a dream come true. In fact, it feels surreal. If you'd asked me when starting SpaceX if this would happen, I'd be like, 1% chance, 0.1% chance."

A successful culmination to Demo-2 would also make it the first crewed commercial spaceflight mission ever, opening a new era of space exploration.

You can watch the astronauts' return live here.

'American astronauts on American rockets from American soil'

Russia has used its spaceflight monopoly to charge more and more per round-trip ticket for each NASA astronaut. The cost has risen from about $21 million in 2008 (before the shuttle was retired) to more than $90 million per seat on a planned flight for October.

A seat on SpaceX's Crew Dragon, meanwhile, is projected to cost $55 million, according to NASA's inspector general. While Soyuz can carry only three people at a time, the Crew Dragon can seat seven.

That's one reason NASA began funding SpaceX and its competitor, Boeing, to develop human-ready spacecraft in 2010. The effort, called the Commercial Crew Program, is three years past its original deadline.

In addition to giving NASA better access to the space station, having a spacecraft and launch system in the US would enable the agency to use the space station's microgravity environment to conduct more science experiments — in pharmaceuticals, materials science, astronomy, medicine, and more.

Other countries would benefit from a commercial US option, too, since they could turn to either SpaceX or Soyuz depending on their needs.

"The International Space Station is a critical capability for the United States of America. Having access to it is also critical," Jim Bridenstine, NASA's administrator, said during a briefing on May 1. "We are moving forward very rapidly with this program that is so important to our nation and, in fact, to the entire world."

Demo-2 brings SpaceX one step closer to the moon and Mars

SpaceX has big plans. Musk dreams of flying people around the moon and later landing on the lunar surface, then moving on to establish Martian cities and put a million settlers on the red planet.

SpaceX also plans to fly space tourists. In February, the company announced that it had sold four seats through a spaceflight tourism company called Space Adventures. Then in March, news broke that Axiom Space — led in part by a former ISS mission manager at NASA — had also signed a deal with SpaceX.

Even Tom Cruise intends to fly aboard Crew Dragon so he can film a new action movie on the space station.

NASA shares some of Musk's ambitions (sending humans back to the moon and, eventually, to Mars) but there are a lot of steps along the way. Sending astronauts to the space station aboard the Crew Dragon was the first big milestone.

But the mission won't be considered a success until it returns Hurley and Behnken to Earth.

"We're going to stay hungry until Bob and Doug come home," Kathy Lueders, who manages the Commercial Crew Program for NASA, said in a briefing before the launch. "Our teams are scouring and thinking of every single risk that's out there, and we've worked our butt off to buy down the ones we know of, and we'll continue to look — and continue to buy them down — until we bring them home."

Do you have a story or inside information to share about the spaceflight industry? Send Dave Mosher an email at dmosher+tips@businessinsider.com or a Twitter direct message at @davemosher. More secure communication options are listed here.