Boeing Starliner’s first astronaut flight halted at the last minute

The apparently crossed star Boeing Starliner — just minutes after its much-delayed liftoff on the spacecraft’s first piloted test flight — was grounded again on Saturday when one of the three redundant computers managing the countdown from the base of the launch pad had a problem, triggering a wipeout. last hour.

Engineers have prepared for another launch attempt on Sunday at 12:03 pm EDT, assuming the problem can be resolved in time. A decision was expected later Saturday, after troubleshooters gained access to the suspect hardware and carried out inspections.

The Starliner crew, Commander Barry “Butch” Wilmore and co-pilot Sunita Williams, arrived about two hours after launch on May 6, only to be derailed by problems. with pressure relief valve on its Atlas 5 rocket, and a helium leak in the capsule’s propulsion module.

These issues have been resolved, and after a few minor issues on Saturday, the countdown appeared to be moving smoothly towards the planned launch at 12:25 pm EDT. But 10 seconds after the countdown ended from a planned wait at the T minus 4 minute mark, the clocks suddenly stopped ticking.

Launches to the International Space Station are timed to the moment when the Earth’s rotation aligns the platform with the space station’s orbit, a requirement when trying to find a target moving at nearly 5 miles per second. An unplanned interruption in the countdown for such missions immediately triggers a minimum launch delay of 24 hours.

Tory Bruno, CEO of United Launch Alliance, builder of the Atlas 5 rocket, said the problem Saturday involved one of three racks of networked computers in a building at the base of the launch pad. Each rack has multiple systems, including identical circuit boards that operate together as a “ground launch sequencer,” managing the final steps of a countdown.

The GLS’s computers manage events such as the retraction of the umbilicals and the firing of explosive beams that release the rocket from the pad for liftoff, and all three must be in perfect agreement for the countdown to proceed.

During Saturday’s launch attempt, the countdown reached T minus 4 minutes and then entered a planned four-hour hold. When the countdown resumed four minutes before takeoff, one of the GLS’s three circuit boards took longer than expected to synchronize with the other two. This was enough to trigger an automatic hold at the T mark for less than 3 minutes and 50 seconds.

Engineers planned to begin troubleshooting after draining the Atlas 5’s liquid hydrogen and oxygen propellants 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, although disappointed, overcame the latest delay.

“You know when you’re playing and you get a bad call, you get a little angry at first, or a little frustrated at first, but you immediately focus on the next pitch and that’s what our teams do, they’re focused on the next step,” said Mark Nappi, Boeing’s Starliner project manager.

“As soon as we started the launch cleanup and turnaround, I looked into the control room and everyone was with their heads down, working through procedures to prepare for another attempt tomorrow.”

Said Bruno: “The disappointment lasts about three seconds. And then you immediately get busy and do your job. We’ll be back.”

Whenever it lifts off, the long-awaited flight will be the first piloted launch of an Atlas 5 and the first in the Atlas family of rockets since astronaut Gordon Cooper lifted off just a few miles away on the final flight of the Mercury program 61 years ago. .

Likewise, it will be the first piloted flight of the Starliner, Boeing’s answer to SpaceX’s Crew Dragon, an already operational and cheaper spacecraft that has transported 50 astronauts, cosmonauts and civilians to orbit in 13 flights, 12 of them to the space station , since a first piloted test flight in May 2020.

NASA funded the development of both spacecraft to ensure the agency would be able to launch crews to the outpost even if a company’s ferry became stranded for any reason.

Already years behind schedule due to budget shortfalls and a variety of technical problems that cost Boeing about $1.4 billion to fix, NASA had hoped to put Starliner into orbit on May 6. a pressure relief valve on the rocket’s Centaur upper stage.

The Atlas 5 was removed from the platform and back to the ULA Vertical Integration Center, where the Centaur valve was quickly replaced. But after launch, Boeing engineers saw signs of a small helium leak in the Starliner’s propulsion system.

The leak was traced to a flange in the plumbing that supplied pressurized helium to drive a specific jet of the reaction control system in the Starliner’s service module. The leak was characterized as “very small,” but engineers needed to show that it wouldn’t worsen drastically during flight and cause problems for other thrusters.

After extensive analysis and testing, mission managers concluded that the spacecraft could be launched safely as is, saying that even if the escape rate were a hundred times worse than observed so far, it would not pose a risk to the crew. or for the mission. Ultimately, the leak rate remained within acceptable limits on Saturday.

If the mission is unable to lift off on Sunday, NASA will have two more opportunities next week, one at 10:52 a.m. EDT Wednesday and another at 10:29 a.m. EDT Thursday. After that, ULA will have to transport the rocket back to the integration facility to replace the batteries in the booster’s self-destruct system. Bruno said that the work, if necessary, would take around 10 days.