The Boeing Starliner faced a critical situation during its approach to the International Space Station (ISS), where multiple thruster failures brought it within minutes o losing full control and potentially endangering the crew. Ars Technica got the details from Astronaut Wilmore on the danger 9 months ago during the docking.
The Starliner was likely 30-60 seconds from total loss of control and potential crew loss if a fifth thruster had failed before the first reset, or if the reset had not restored functionality. The critical period spanned the minutes between the fourth failure (loss of 6DOF) and the successful reset, with Wilmore’s manual skill and Mission Control’s quick decision-making bridging the gap. The crew’s decision to prioritize docking over an uncertain deorbit burn, combined with the partial thruster recovery, narrowly averted disaster.
The progression from the third to the fourth thruster failure appears to have occurred over a span of minutes during the final approach (within 260 meters of the ISS). After the fourth failure, Starliner had lost 6DOF control, and any additional failure (e.g., a fifth thruster before the reset) could have rendered it uncontrollable within seconds, depending on the spacecraft’s drift and Wilmore’s ability to compensate manually. The reset of two thrusters likely occurred within 1-2 minutes of the “hands off” call, averting a total loss of control by a narrow margin—potentially 30-60 seconds if another thruster had failed during that window.
The NASA and Boeing coverage did not talk about the failing thrusters.
The sequence of events was as follows:
Initial Concern and First Thruster Failure: Before the mission, Astronaut Wilmore expressed concerns about the thrusters due to prior issues during uncrewed tests (OFT missions). During the approach to the ISS, the first thruster failed, reducing redundancy but not yet compromising control.
Second Thruster Failure (Single Fault Tolerance): As Starliner neared the V-bar (velocity vector), approximately 260 meters from the ISS, a second thruster failed. This left the spacecraft “single fault tolerant,” meaning one more failure would risk losing 6DOF control, triggering a mandatory abort under standard flight rules. Wilmore took manual control at this point.
Third Thruster Failure (Zero Fault Tolerance): After acquiring the V-bar, a third thruster failed, all in the same direction (aft, bottom thrusters). This brought Starliner to “zero fault tolerance,” meaning no further failures could be sustained without losing full control. Control became sluggish, though Wilmore could still maintain it manually.
Fourth Thruster Failure (Loss of 6DOF Control): A fourth thruster failed, resulting in the loss of 6DOF control. Wilmore could no longer maneuver forward, though he retained partial control over other axes. This was a critical moment, as the spacecraft’s ability to dock or safely deorbit was in jeopardy. The crew considered docking as the safer option compared to attempting reentry with compromised thrusters.
Thruster Reset and Partial Recovery: Mission Control instructed Wilmore to go “hands off,” and a reset command was sent, recovering two of the four failed thrusters. THIS WAS A CRITICAL REBOOT of the engines.
This briefly restored single fault tolerance. aka Two thrusters were recovered.
However, a fifth thruster then failed, returning the spacecraft to zero fault tolerance.
IF the reboot was not done before the fifth thruster failed then Starliner could have started tumbling out of control.
A second reset attempt recovered all but one thruster, allowing autonomous docking to proceed successfully.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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Trump administration has stated that the F-47 development contract will go to Boeing (Boing). That’s scary. Very scary! Strongly recommend reconsideration.
Yes quite an amazing story and cause for very serious concern about the company’s competence. Such failures should not be happening at that point in the timeline.
I was an independent contractor working at Boeing years ago. I was convinced that if FAA contractors weren’t signing off on major manufacturing milestones Boeing planes would regularly fall out of the sky.
My late uncle was V.P. for International Sales at Boeing for about 2 decades in the late 70s-early 90s. He gave me tour of the assembly line in Seattle once. All he talked about was engineering aspects – tolerances, metallurgy of materials, etc…and he wasn’t even an engineer! Things were so different before the MBA’s and people who put profits over engineering took over and ruined what was once one of America’s premier companies. My uncle also complained about how European subsidies gave Boeing’s chief competitor Airbus an advantage over privately controlled Boeing, also highlighted in this old Smithsonian article that quotes him too: https://www.smithsonianmag.com/air-space-magazine/the-contender-3630193/. It’s hard to imagine anyone thinking a multi-national EU government consortium would be considered an engineering and development threat today; that’s reserved for China now.
The wheels have come off the bus at so many levels today, it’s hard to remember when things generally worked, and progress was assumed.
Yes, the current administration SAYS it’s going back to emphasizing merit over everything else, but then when you look at the people running the government, it’s hard to believe anything other than loyalty to the president matters much. And chaos and dysfunction seems to be a goal unto itself, including from the country’s chief technologist, who has governing powers no other person in his position would even have had before, or even aspired to have because there were plenty of other competent people around.
It wasn’t always like this.
Boeing cannot built a good or safe aircraft now considering all the problems and tools left one them. What makes anyone think they can build good spacecraft or military planes?
X plains rhe happy faces when they touched down on planet earth.
I get it, that was a hairy situation, but that’s why all the protocols followed were instituted, right? I’m guessing – like anything – there are a lot of “ifs” involved that could lead to disaster. “If” the O rings fail – disaster. “If” the heat shield is damaged and tiles are lost – disaster. “If” an explosion in oxygen tank number two of the service module, which ruptured and damaged the number one tank, leading to a loss of oxygen, power, and water happens, and the problem wasn’t resolved – disaster. Space, and travel to and through it is still a dangerous endeavor. More routine now, but still dangerous. The men and women that accept the challenge to climb aboard these spacecraft know and accept the potential risks. They may not expect certain situations to arise, but they certainly know they exist.
The fifth thruster did fail. If the reboot did not happen after the fourth thruster failed, they clearly would have huge trouble. The reboot with five failed thrusters would have been crazy with two directions lost.
As far as I can remember this has been kept in secret for months!
The helium problems were much more serious than that with direct danger to ISS and the star liner crew.
That’s explain why Boeing is evaluating to shutdown all the Space division
And Sunita Williams says she would fly in Starliner again, I wouldn’t take it around the block so to speak 🥺😳😇
Wow… yes it’s a dangerous job but you expect and rely on engineers and manufacturers to do their do diligence to ensure that what they make will not create a life safety issue… every thing you listed could have been prevented if people did their job…