First astronaut flight of the Boeing Starliner aborted at the last minute

The seemingly unlucky Boeing Starliner — just minutes after its long-delayed launch on the spacecraft's first manned test flight — was grounded again Saturday when one of the three redundant computers controlling the countdown from the base of the launch pad encountered a problem that forced a last-minute abort.

Engineers were initially told to prepare for another launch attempt on Sunday at 12:03 p.m. EDT, assuming the problem could be fixed in time. But NASA later announced the team would forego a launch attempt on Sunday to give engineers more time to assess the computer problem.

The Starliner test flight includes a rendezvous and docking with the International Space Station. Depending on the station's orbit and the Starliner's ability to catch up, the next two launch opportunities after Sunday are Wednesday at 10:52 a.m. EDT and Thursday at 10:29 a.m. NASA said the agency will provide an update on Sunday.

The Starliner crew, Commander Barry “Butch” Wilmore and co-pilot Sunita Williams, arrived about two hours before launch on May 6, but were then delayed by problems. with pressure relief valve in their Atlas 5 rocket and a Helium leak in the capsule's drive module.

Those issues were resolved, and after a few minor hiccups, the countdown appeared to be running smoothly Saturday until the launch was scheduled to take place at 12:25 p.m. EDT. But 10 seconds after the countdown emerged from a planned pause at the T-minus-4 minute mark, the clocks suddenly stopped.

Launches to the International Space Station are timed to coincide with the moment when Earth's rotation brings the launch pad into alignment with the space station's orbit, a prerequisite for rendezvous with a target moving at nearly 8 kilometers per second. An unplanned interruption in the countdown for such missions immediately results in a launch delay of at least 24 hours.

Commander Barry “Butch” Wilmore (right) and co-pilot Sunita Williams buckle up for launch on board Boeing’s Starliner spacecraft.


Tory Bruno, CEO of United Launch Alliance, the manufacturer of the Atlas 5 rocket, said Saturday the problem affected one of three networked computer racks in a building at the base of the launch pad. Each rack is equipped with several systems, including identical circuit boards that together act as a “ground launch sequencer,” controlling the final steps of a countdown.

The GLS computers manage operations such as pulling in the umbilicals and firing the explosive bolts that release the rocket from the launch pad for liftoff. All three operations must be perfectly coordinated for a countdown to begin.

During the launch attempt on Saturday, the countdown ran until T-minus 4 minutes and then paused for four hours. When the countdown resumed four minutes before launch, one of the three GLS boards took longer than expected to synchronize. This was enough to trigger an automatic pause at T-minus 3 minutes and 50 seconds.

The crew is strapped into Boeing's Starliner spacecraft and their Atlas 5 rocket is ready for launch.


Engineers planned to begin troubleshooting after draining the liquid hydrogen and oxygen fuels from Atlas 5 and gaining access to the computer room. The decision on how to proceed depended on isolating the problem and replacing and testing any suspect components.

The launch team was disappointed but took the recent delay in their stride.

“You know when you're playing a game and you get a bad decision, you're a little irritated or frustrated at first, but you immediately focus on the next pitch, and that's exactly what our teams do: They focus on the next pitch,” said Mark Nappi, Boeing's Starliner project manager.

“As soon as we started the launch abort and launch reversal phases, I looked into the control room and everyone was busy with their heads down, going through the procedures to prepare for another attempt the next day.”

Bruno said: “The disappointment lasts about three seconds. And then you get straight to work. We'll be back.”

Whenever the flight lifts off, it will be the first manned launch of an Atlas 5 and the first of the Atlas family of rockets since astronaut Gordon Cooper blasted off just miles away on the final flight of the Mercury program 61 years ago.

It will also be the first manned flight of the Starliner, Boeing's answer to SpaceX's Crew Dragon, an already operational, less expensive spacecraft that has carried 50 astronauts, cosmonauts and civilians into orbit in 13 flights since a first manned test flight in May 2020, including 12 to the space station.

NASA funded the development of both spacecraft to ensure that the agency could send crews to the outpost even if either company's transfer ship were grounded for some reason.

NASA had been behind schedule for years due to budget cuts and a series of technical problems that cost Boeing about $1.4 billion to fix. It had hoped to put the Starliner into orbit on May 6, but the launch was aborted when United Launch Alliance engineers discovered a problem with a pressure relief valve in the rocket's Centaur upper stage.

The Atlas 5 was brought from the launch pad back to ULA's Vertical Integration Facility, where the Centaur valve was quickly replaced. But after the launch was aborted, Boeing engineers discovered signs of a small helium leak in the Starliner's propulsion system.

The leak was traced to a flange in the pipeline that delivered pressurized helium to power a specific reaction control nozzle in the Starliner's service module. The leak was described as “very small,” but engineers had to show that it would not drastically worsen during flight and cause problems for other engines.

After extensive analysis and testing, mission managers concluded that the spacecraft could be launched safely as it is. Even if the leak rate were a hundred times higher than previously observed, it would not pose a risk to the crew or the mission. As it turned out on Saturday, the leak rate remained within acceptable limits.