In a significant development for Boeing's Starliner spacecraft, it is set to leave the International Space Station (ISS) on Friday after months of delays. However, the return journey will be devoid of the two astronauts it carried into orbit in June, due to ongoing issues with its propulsion system. The capsule's departure marks a setback for Boeing and NASA's Commercial Crew Program.

Originally scheduled for a much earlier departure, the Starliner spacecraft remained at the ISS for approximately three months while Boeing tackled problems with its thrusters. Nevertheless, company officials consistently assured the public that the spacecraft was safe for the astronauts.

NASA's Butch Wilmore and Suni Williams, the two test pilots who were intended to return aboard the Starliner, will now extend their stay at the ISS for the remainder of the year. Instead, they are set to return to Earth in February 2022 aboard SpaceX's Dragon spacecraft.

The hatch of the Starliner capsule, named "Calypso," was sealed on Thursday, in preparation for its departure at approximately 6 p.m. ET on Friday. The undocking process will differ from a crewed mission to ensure the protection of the ISS, without the ability for manual control.

Once undocked, the Starliner spacecraft is expected to take around six hours to complete its journey back to Earth, landing at White Sands Space Harbor in New Mexico. This extended stay and delayed return of the Starliner have been primarily driven by NASA's determination to gather more data on the spacecraft's problematic propulsion system.

The Starliner's return, albeit empty, is seen as a crucial test flight for Boeing and a significant milestone for NASA. The space agency had aimed to have two competing companies, Boeing and SpaceX, providing alternate missions to the ISS.

With the additional delays and over $1.5 billion in losses already incurred, Boeing's future involvement in NASA's Commercial Crew Program hangs in the balance. The setback for Boeing also emphasizes the growing significance of SpaceX's Dragon spacecraft, as it continues to successfully transport astronauts to and from the ISS.

As the developments unfold, the repercussions and implications of Boeing's Starliner setbacks will likely continue to shape the future of space exploration and commercial crew transportation. Updates on this evolving story will be provided as they become available.