It’s a Scrub for Boeing Starliner’s First Crewed Spaceflight

The first crewed spaceflight of Boeing’s Starliner was scrubbed tonight because of unexpected behavior in an oxygen relief valve on the rocket’s upper stage. NASA astronauts Butch Wilmore and Suni Williams were settling into their seats inside the spacecraft when the United Launch Alliance decided “out of an abundance of caution” to cancel the launch for tonight. ULA engineers will be working overnight to determine the status of the valve before deciding when they can try again.

The decision to delay the Crew Flight Test (CFT) launch was made by Tom Heter III, ULA’s Launch Director. Starliner uses ULA’s Atlas V rocket, which has a 100 percent mission success record.

ULA Launch Director Tom Heter III has made the decision to the launch team that launch operations will not continue tonight for #AtlasV and #Starliner.https://t.co/yCCjHu9R5K

— ULA (@ulalaunch) May 7, 2024

The troublesome valve is in the rocket’s Centaur upper stage.

#AtlasV fun facts#Starliner // #CFT

Height: 172-foot-tall (52 meters)

Mass at liftoff: 979,000-pound (444,000-kg)

Thrust: 1.6 million pounds (7.1 megaNewtons)

Webcast: https://t.co/yCCjHu9R5K pic.twitter.com/i33DR3X0Cg

— ULA (@ulalaunch) May 6, 2024

During a press briefing following the scrub, ULA President Tory Bruno explained that these valves can operate for 200,000 full cycles, but in rare instances as they age they do not seat properly and “buzz” or “flutter.” When this has happened in the past, ULA simply recycles the valve and proceeds with launch. However, this is the first time the Atlas V has been used to launch people and ULA established flight rules that do not allow the rocket’s fuel state to be changed when the crew is aboard. Recycling the valve with the crew in the capsule is prohibited, so they scrubbed the launch.

ULA now needs to determine exactly how many full cycles the valve has experienced. The valve does not have sensors to record that data, but it can be inferred by looking at acclerometers on the nearby RL-10 engines, Bruno said. There’s a “fair chance” they will know by tomorrow if it’s within the 200,000 limit or needs to be replaced. If it’s within the limit, the launch could take place tomorrow. If not, the rocket will have to be returned to ULA’s Vehicle Integration Facility. In that case the launch is “unlikely” before Sunday.

Asked if there are other valves that need to be checked, Bruno said they’ve already done that.

Bruno and NASA Commercial Crew Program Manager Steve Stich weren’t certain of the exact timing of when they needed the answer in order to launch tomorrow, but Stich said there is a weather briefing 8 hours before launch and they would want to know by then. The launch time tomorrow is 10:11 pm ET, so that would put it at about 2:00 pm ET. Other opportunities are on May 10 at 9:00 pm ET and May 11 at 8:38 pm ET.

Meanwhile, the two crew members exited the spacecraft and returned to crew quarters to await news of steps forward.

When Williams and Wilmore arrived at Kennedy Space Center last week, Williams made a point of saying that launch dates are not set in stone. She mentioned that she and Doug Hurley, one of the two astronauts who flew on SpaceX’s equivalent of this test flight, were texting about how a delay actually takes the pressure off. Hurley’s flight with Bob Behnken on Demo-2 in 2020 was delayed by weather 17 minutes before launch.

NASA’s standard refrain for any human spaceflight launch is that they will go when they are ready. Period.  NASA Administrator Bill Nelson said just that this evening.

Standing down on tonight’s attempt to launch #Starliner. As I’ve said before, @NASA’s first priority is safety. We go when we’re ready. https://t.co/KIasomZG66

— Bill Nelson (@SenBillNelson) May 7, 2024

This article was updated following the press conference.