Starliner’s Crew Flight Test Comes to an End

Boeing’s Starliner capsule undocked from the International Space Station at 6:04 pm ET and is on its way to a landing in New Mexico about 5 hours from now at midnight ET.  That will bring to an end the Crew Flight Test although the crew — NASA astronauts Butch Wilmore and Suni Williams — are not aboard. Concerns about Starliner’s thrusters led NASA to decide to leave them on the ISS and bring Starliner back to Earth empty.

The capsule, named Calypso, autonomously separated from the ISS.  Springs pushed it away initially and then Starliner’s Reaction Control System (RCS) thrusters fired 12 times to move it further away to begin the trip back to Earth.

#Starliner has undocked from the @Space_Station and will begin its journey back to Earth.@NASA and @BoeingSpace are targeting approx. 12am ET Sept. 7 for the landing and conclusion of the Crew Flight Test mission at the White Sands Space Harbor, New Mexico landing site. pic.twitter.com/uB0DgmUUPW

— NASA Commercial Crew (@Commercial_Crew) September 6, 2024

All 12 thruster burns went as planned.

Those thrusters are the reason no one is aboard Starliner on this last leg of its journey, however.

Launched on June 5, Starliner arrived at the ISS exactly two months ago on June 6. During its approach, five of the 28 RCS thrusters didn’t operate because software “deselected” them. Starliner also experienced four helium leaks in addition to one discovered prior to launch.

Four of the thrusters later came back online, but ground- and space-based tests over the subsequent weeks left enough questions in NASA’s mind that they decided not to risk putting Butch and Suni onboard for the return trip. Instead they will become part of the next regular crew rotation, Crew-9, and return with them on SpaceX’s Crew Dragon in February.

What Boeing and NASA have determined so far is that overheating caused “poppet” seals in some of the aft thrusters to swell, restricting the flow of propellant. Boeing developed models to explain what happened and was confident the thrusters would be fine for reentry, but NASA didn’t agree.  Butch and Suni are NASA astronauts and it was NASA’s decision to make.

This is the third flight of Starliner, but the first with a crew. An uncrewed Orbital Flight Test (OFT) in 2019 experienced significant problems and Boeing decided to refly it before putting people on board.  It was two-and-a-half years before they were ready to try again. Orbital Flight Test-2 (OFT-2) went well  in 2022, but other problems arose after that and this Crew Flight Test was delayed until now.

Starliner is Boeing’s competitor to SpaceX’s Crew Dragon to ferry astronauts to and from the ISS every six months. NASA’s goal is to fly one Starliner and one Crew Dragon every year. It wants two dissimilar systems for redundancy and competition.

SpaceX has been launching crews for NASA since 2020, but Boeing is far behind. It hoped this flight would lead to NASA certification of Starliner and the beginning of operational flights in February 2025, but NASA has already said it will use a Crew Dragon for that rotation. The earliest Starliner will fly again is August 2025 and that’s only if Boeing can fix the problems and win NASA certification by then.

Starliner is being built as a Public-Private Partnership and Boeing, not the government, must pay for cost overruns. Boeing has spent $1.6 billion of its own money already.

 

This article will be updated after landing.