NASA astronauts stuck on Boeing spacecraft face high stakes return from ‘incredibly important mission’: expert

The two NASA astronauts stuck on Boeing's Starliner spacecraft have an approximate return-by date of July 20. 

That's 45 days from its June 5 liftoff, which is how long Starliner can spend docked to the International Space Station (ISS). 

Astronauts Suni Williams and Butch Wilmore's original stay was scheduled for a week, but a series of issues, including recent helium leaks and thruster problems, pushed their homecoming back multiple times. 

"Operating in space, building these spacecraft, especially human-rated spacecraft for commercial companies, is a new endeavor that's still incredibly technical," Makena Young, a fellow with the Aerospace Security Project at the Center for Strategic and International Studies (CSIS), told Fox News Digital. "It's a really hard operating environment when things go wrong ... It's not like you can go to take it to a mechanic when you're in space."

WILL IT BE ASKED DURING THURSDAY'S DEBATE? PUSH TO ASK PRESIDENT CANDIDATES ABOUT UFO DISCLOSURE

NASA and Boeing didn't immediately respond to Fox News Digital's questions.

Boeing told Newsweek late Tuesday afternoon that a majority of the helium leaks and thruster problems have been stabilized and are "not a concern" for Starliner's safe return. 

SPACE JUNK RIPS THROUGH US FAMILY'S HOME WITH PEOPLE INSIDE

Only one of Starliner's 27 thrusters remains offline, Boeing told Newsweek, and four of the five thrusters that were shut down are operating normally. 

A return date hasn't been officially scheduled yet, but Reuters cited a NASA source who said the new target return date is July 6.

NASA's most recent update came Monday, when Steve Stich, manager of NASA’s Commercial Crew Program (CCP), said the team is "taking our time and following our standard mission management team process." 

"Starliner is performing well in orbit while docked to the space station," Stich said in a statement.

ENERGY CZAR MAKES UFO ADMISSION DURING GOP LAWMAKER'S FIERY EXCHANGE

"We are strategically using the extra time to clear a path for some critical station activities while completing readiness for Butch and Suni’s return on Starliner and gaining valuable insight into the system upgrades we will want to make for post-certification missions."

Family members of the astronauts declined comment, or didn't return Fox News Digital's calls.

Boeing and the Elon Musk-funded SpaceX programs are pivotal players in NASA's CCP, which would allow NASA to send astronauts and cargo to the ISS without relying on Russia.

Young said NASA has paid almost $2 billion to Russia to get 30 astronauts to the ISS and back after retiring the shuttle in 2011.

WATCH: FOX NEWS REPORT ON NASA'S END OF SHUTTLE PROGRAM

Instead of paying the "hefty price tag" to an adversarial country, NASA turned to private U.S. companies to get people and humans to the space station. 

"This is an incredibly important mission," Young said. "These delays seem like a bad thing, and can erode confidence that you have in the system … but you really want to make sure that there are no questions in the back of your mind when you're saying, ‘OK, yes, this is ready to launch humans.’ They're definitely necessary."

UFOS AREN'T JUST IN THE AIR; THEY'RE UNDERWATER AND ‘JEOPARDIZE MARITIME SECURITY’: EX-NAVY OFFICER

This was Boeing's inaugural mission to bring humans to the ISS, while SpaceX's Dragon craft has had several successful trips. 

This exact predicament illustrates the need to have at least two reliable options to get to and from the ISS, Young said.

WATCH: SPACEX DRAGON CAPSULE

After 45 days are up, Young said Starliner can operate another 72 days on backup power. 

If, for some reason, the situation turns into a critical emergency and a race against the clock, SpaceX would likely prep a rescue mission with NASA, Young said, although she believes the issues will be resolved before it reaches that level. 

WATCH: AT LEAST TWO ALIENS ‘TRY TO STAVE OFF PESKY HUMANS’: CRIME SCENE RECONSTRUCTION EXPERT

"But it's a great point to underscore as well, that these astronauts are not stranded because NASA does have this other system that is reliable and proven," she said. 

"That's why NASA always has a redundancy, so that if something does go wrong with one program, the other is able to easily step in."