NASA entered a new chapter in its prestigious history of space exploration when the shuttle was retired in 2011 after 30 years.
The space agency relied on Russia to get U.S. cargo and astronauts to the International Space Station (ISS), which cost about $90 million per astronaut for a round trip.
Under former President Obama, NASA turned to private U.S. companies to create a spacecraft to be less reliant on a geopolitical adversary.
The Boeing Company and Elon Musk-funded SpaceX were awarded contracts in a public-private space exploration partnership, but each company had several starts and stops during development.
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That delayed the anticipated 2018 initial launch, but SpaceX worked out its kinks first.
The SpaceX Dragon Crew successfully launched two astronauts to the ISS in 2020 and returned them home without a hitch.
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Boeing's Starliner spacecraft made its inaugural human-manned launch June 5, but a series of issues in space delayed the astronauts' homecoming.
Astronauts Suni Williams and Butch Wilmore, who were aboard Starliner, remain at the ISS for the foreseeable future as engineers fix the helium leaks and thruster issues before bringing them back to Earth.
That was the most recent hiccup in years of starts and stops during the development phase of SpaceX's and Boeing's crafts.
1. SpaceX's and Boeing's spacecraft were developed under NASA's Commercial Crew Program after the shuttle was retired.
2. NASA awarded Boeing and SpaceX contracts of $4.2 billion and $2.6 billion, respectively, after a lengthy open competition in September 2014.
The public-private partnership is expected to drop the cost per seat from $90.3 million, which was being paid to Russia, to $69.9 million for U.S. companies, according to a NASA report.
3. By 2024, SpaceX and Boeing were anticipated to provide ISS access for at least 48 astronauts, according to a 2019 NASA audit.
That expectation wasn't realized because each company faced "significant safety and technical challenges with parachutes, propulsion and launch abort systems," the 2019 audit said.
4. SpaceX successfully launched and returned its first manned craft in May 2020 and has completed several successful missions since.
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"Space is extremely difficult," expert Makena Young told Fox News Digital in an interview. "SpaceX has really just been the outlier and figured it out, in my opinion, with a lot of success."
Young is a fellow with the Aerospace Security Project at the Center for Strategic and International Studies.
5. Boeing's manned crew mission was bumped several times after tests in December 2019 failed to fix technical glitches. In 2022, Starliner's unmanned craft reached the ISS, but more issues with the parachute were discovered in 2023.
That delayed the manned mission again.
6. Boeing's Starliner successfully launched its first manned craft to the ISS June 5, but a series of issues plagued the craft and delayed the astronauts' homecoming.
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There were helium leaks in the propulsion system and faulty thrusters engineers have been fixing over the last three weeks.
The helium leaks "are all stable and not a concern for a return mission," Boeing told Fox News Digital in an email Thursday, and four of the five thrusters that were shut down are "operating normally."
Starliner remains docked at the ISS, where it can stay for 45 days. A new date to return the astronauts to Earth hasn't been set yet.
This predicament illustrates the need to have at least two reliable options to get to and from the ISS, Young said.
"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," Young 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."
