NASA has delayed the return of two astronauts from the International Space Station (ISS) for a third time, raising concerns that the crew could be “locked out”.

Butch Wilmore and Shuni Williams were originally scheduled for a nine-day stay, which was postponed twice this month and is now on an unspecified date.

DailyMail.com spoke to experts who said NASA could be forced to launch a rescue mission and could use Elon Musk’s SpaceX to carry it out.

Katsuo Kurabayashi, professor of aerospace engineering at New York University, said: “Given the current situation with the Starliner, it is possible that NASA will decide to use an alternative spacecraft, such as SpaceX’s Crew Dragon, to bring the astronauts home with security.

He adds that: “As far as I can tell at this point, the recent mission delay in July alone should not raise serious concerns that will lead to another extremely demanding rescue mission or the future abandonment of Starliner-based missions.” .

“But if they start talking about a rescue mission by accident, it would indicate that there are some serious, potentially life-threatening hardware defects found with the Starliner.”

The return of the astronauts was initially postponed to June 14, and last week it was rescheduled for June 26.

It is recalled that the Starliner took off on June 5 at 10:52 am. ET from the Cape Canaveral space station in Florida last week with a leak that had to be addressed in May.

The Boeing Starliner carrying the two astronauts started with a known leak that was reportedly no bigger than a shirt button and quite subtle.

However, the Starliner experienced five failures in its 28 maneuvering thrusters, five leaks of helium gas intended to pressurize those thrusters, and a slow propellant valve that signaled uncorrected past problems since launch.