After a summer of turmoil, Boeing Starliner spacecraft is heading home – without astronauts on board.
The unmanned capsule undocked from the International Space Station at 6:04 p.m. ET Friday as the orbiting lab flew 260 statute miles above central China. The departure marked the beginning of a roughly six-hour journey back to Earth that will culminate with a landing at White Sands Space Port in New Mexico shortly after midnight.
NASA said that if weather conditions are favorable, residents of southwest and western Mexico will be able to see Starliner streaking across the sky toward the landing site.
Starliner launched to the space station with NASA astronauts Butch Wilmore and Suni Williams in early June. It was the capsule's first crewed test flight, and the mission is expected to last about eight days. But problems with spacecraft engines and an unexpected helium leak in its propulsion system forced Starliner to remain in space for the last three months while engineers on Earth assessed how to safely return it to Earth.
After weeks of testing and analysis, NASA determined that the capsule's propulsion system appeared stable, but the engine problems posed too great a risk to the Starliner's return with a crew. The space agency decided to keep Wilmore and Williams aboard the space station into the new year and send them return to Earth in February instead on a SpaceX capsule.
Wilmore and Williams were on hand to help Starliner leave the space station.
“We'll support you, and you do this,” Williams radioed mission controllers at Johnson Space Center in Houston before the capsule undocked. “Get her back to Earth. Good luck.”
Starliner's return will be closely watched because it marks the end of a dramatic few months for Boeing and NASA. The test flight was meant to demonstrate that the spacecraft could reliably carry astronauts to and from low Earth orbit, paving the way for NASA to certify Boeing for regular flights to the space station.
Instead, the engine problems were the latest major setback for Boeing’s Starliner program, which was more than $1.5 billion over budget and years behind schedule even before launch. The uncrewed test flight that NASA required Boeing to complete before its spacecraft could carry astronauts also went awry the first time around, forcing the company to repeat it in 2022.
Earlier this week, NASA officials said the space agency was working with Boeing on modifications to Starliner's engines. Additional analysis will be done after the spacecraft returns and engineers can assess how it is performing.
To account for potential engine failures as Starliner began its journey home, flight controllers modified the capsule's normal undocking process. After detaching from the space station, Starliner autonomously took off and flew away from the station to protect it in case anything went wrong.
Preliminary data showed the engines performed well during all 12 planned backward burns, NASA said.
A few hours later, at 11:17 p.m. ET, Starliner's engines will fire a 59-second “trigger” to slow the spacecraft and send it plummeting through Earth's atmosphere. As it approaches its landing site in New Mexico, parachutes will deploy to slow the capsule, and airbags will deploy beneath the spacecraft to cushion its landing.
For Boeing, a successful return of the Starliner capsule would likely be bittersweet. If all goes well, it could mean NASA astronauts could return home safely on the spacecraft, though top agency officials voted unanimously to urge SpaceX to back out of the mission to minimize the risk of additional disruptions.
Boeing developed its Starliner spacecraft as part of NASA's Commercial Crew Program, an initiative launched in 2011 to support private spacecraft to fill the gap left by NASA's retired space shuttles. Rival SpaceX developed its Crew Dragon spacecraft as part of the same program and has been flying regularly to and from the space station since 2020.
This article was originally published on NBCNews.com