NASA astronauts from Boeing's troubled Starliner capsule are facing being stranded in space until August after a series of tech glitches.
Sunita Williams and Butch Wilmore have been left in a limbo for weeks after riding the faulty capsule to the International Space Station.
The astronauts were only supposed to stay aboard the ISS for a maximum of one week before landing back on Earth on June 13.
However, throughout the 25-hour voyage, Boeing's Starliner spacecraft ran across a number of issues, which triggered delays to their return.
Wilmore and Williams are now expected to remain in space until the middle of August while crews on Earth scramble to fix the problem.
Nasa said on Wednesday that mission managers were not yet prepared to schedule the craft's departure.
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The space agency continues to conduct tests to ensure the capsule would function as intended.
Steve Stich, Nasa’s commercial crew program manager, said at a lunchtime press conference: “Some of the data suggests optimistically, maybe it’s by the end of July, but we’ll just follow the data each step at a time.
“We’re going to work methodically through our processes, including a return flight readiness review with the agency, before we get the go to proceed towards undocking and landing.
“This is a very standard process.”
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Starliner departed from Florida's Cape Canaveral on June 5 in what would be its first crewed flight.
However, one day after liftoff, five separate helium leaks to the spacecraft's thruster system were recorded as the spacecraft got closer to the space station.
Four of the five have been activated back thus far, which according to Wilmore should be sufficient to operate the flight home.
Nasa and Boeing are trying to replicate the issues on a new unit at a missile range in New Mexico this week in hopes it would be the key to the astronauts' return.
Wilmore and Williams are assisting with station operations as needed while Starliner remains docked at the ISS.
They join the seven-member Expedition 71 crew, who have been stationed at the ISS since April, exploring neuro-degenerative diseases, space botany, and more.
Stich added that there was no risk to any of the people on board as the space station had enough supplies and resources.
Although the corporation believes the thrusters are undamaged, they added: "We want to fill in the blanks and run this test to assure ourselves of that".
Officials have stated that despite the leaks, there is still plenty of helium available for the return voyage.
Vice President of Boeing Mark Nappi asserted that in the event of an emergency, the Starliner could immediately carry its crew back home.
During the press conference, the stranded astronauts appeared to be optimistic that they will come back safely.
Williams said: “I have a real good feeling in my heart that the spacecraft will bring us home, no problem.
“We trust that the tests that we’re doing are the ones we need to do to get the right answers, to give us the data that we need to come back.
“I’ll just reiterate again this is a test flight, we were expecting to find some things and so we are finding stuff and we’re correcting it and making changes, making updates.”
After thruster testing is finished on Earth, Wilmore added that he's "absolutely confident" that he and his colleague will return safely.
Boeing's Defense, Space & Security division built the spacecraft as part of Nasa's Commercial Crew Program in 2011.
A software error saw Starliner land in the wrong orbit during its first uncrewed test flight in 2019, while a subsequent attempt was hindered by problems with a fuel valve.
After further investigation, the company resolved issues with parachutes and stripped around a mile of flammable tape from the capsule.
The current mission was the third attempt to take Wilmore and Williams to the ISS.
The first didn't pan out due to a faulty oxygen valve on the rocket carrying Starliner, and the second stalled following an error in a ground launch sequence.
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Boeing has high stakes in the success of the mission, especially amid immense pressure for a number of "defective" aircraft after hundreds of deaths, crashes and calamities have been linked back to the company.
The manufacturer has also drawn scrutiny following the deaths of two whistleblowers within weeks of each other - a coincidence that sparked conspiracy theories online.