Boeing's Starliner spacecraft is heading home, albeit with no one inside.

The Starliner left its docking port at the space station just after 6 p.m. ET, according to NASA. The capsule will spend about six hours free-flying through orbit as it slowly makes its descent toward home.

Before the capsule departed, Butch Wilmore and Suni Williams — the two NASA astronauts who flew Starliner to the space station back in June — wished the spacecraft, nicknamed “Calypso” by Williams, luck on its long-awaited and unexpected journey home.

“It is time to bring Calypso home,” Williams said to mission control Friday evening. “You have got this. We have your backs, and you’ve got this. Bring her back to Earth.”

This was Starliner's first crewed mission which was supposed to prove it was finally ready for regular operation after years of delays and going way over budget. But two separate problems cropped up that ultimately resulted in NASA's decision to send it home empty.

It was the capsule’s first crewed test flight, a mission expected to last around eight days. But problems with the spacecraft’s thrusters and leaking helium in its propulsion system unexpectedly kept Starliner parked in space for the last three months, as engineers on the ground assessed how to safely bring it back to Earth.

After weeks of tests and analysis, NASA determined that the capsule’s propulsion system appeared stable, but the thruster issues posed too much of a risk for Starliner to return with a crew. The space agency opted to keep Wilmore and Williams aboard the space station into the new year and have them fly back to Earth in February on a SpaceX capsule instead...

...the thruster issues became the latest major setback for Boeing’s Starliner program, which even before the launch was more than $1.5 billion over budget and years behind schedule. An uncrewed test flight that NASA required of Boeing before its spacecraft could carry astronauts also went awry the first time, and the company had to repeat it in 2022.

Butch Wilmore and Suni Williams will have to wait until February to come home on a Space X Crew Dragon spacecraft. Space X will have to send up a couple extra spacesuits because the ones Williams and Wilmore have are not compatible with the Space X capsule.

For a few weeks, a SpaceX spacecraft that flew the Crew-8 mission to the ISS will be the emergency vehicle available for Williams and Wilmore if the orbiting complex needs evacuation. But the Starliner suits are not compatible with SpaceX's Crew Dragon spacecraft, NASA commercial crew manager Steve Stich told reporters during a teleconference yesterday (Sept. 6). "So in a temporary situation, we would not have suits for Butch and Suni on Dragon," he explained.

Crew-8 already has four spacesuited astronauts occupying its four seats as they conclude a half-year mission in space: NASA's Matthew Dominick, Michael Barratt, Jeanette Epps and Roscosmos cosmonaut Alexander Grebenkin. If required, Williams and Wilmore would ride home with the Crew-8 astronauts on the cargo pallet underneath their Crew Dragon spacecraft's seats.

As Crew Dragon is fully pressurized, there are no nominal issues for the two Starliner astronauts on board, but the tiny risk of depressurization could pose a critical risk.

Chances are none of that will happen, especially because the extra Space X suits should be arriving in a couple weeks. The next Space X Crew Dragon mission lifts off on Sep. 24. It will bring only two astronauts instead of the planned four to allow Wilmore and Williams to ride back with them in February.

NASA published video of the Starliner undocking from the ISS and everything seemed to be going smoothly, with thrusters working as expected. If all continues to go well the capsule will land at White Sands Space Harbor in New Mexico around midnight. This is the first US made capsule to end its descent on land rather than at sea. It uses parachutes to slow down and airbags are used to soften the landing, though in this case that obviously won't matter. You can skip about 20 minutes in to this clip to see the undocking.