The Boeing Starliner, which looked like a star cross, just minutes from its long-delayed liftoff on the spacecraft's first piloted test flight, was grounded again Saturday when one of three redundant computers managing the countdown from the base of the launch pad had a problem, causing a last-minute exfoliation.
Engineers were initially told to prepare for another launch attempt on Sunday at 12:03 p.m. EDT, assuming the problem could be resolved in time. But NASA later announced that the team would pass up Sunday's opportunity to give engineers more time to evaluate the computer problem.
The Starliner test flight includes a rendezvous and docking with the International Space Station. Depending on the lab's orbit and 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 would provide an update on Sunday.
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 a pressure relief valve on their Atlas 5 rocket and a leak. of helium in the capsule's propulsion module.
Those issues were resolved and after some minor hiccups on Saturday, the countdown appeared to be moving smoothly toward a planned 12:25 p.m. EDT launch. But 10 seconds after the countdown came out of a planned pause at the T-minus 4-minute mark, the clocks suddenly stopped ticking.
Space station launches are timed for the moment when Earth's rotation aligns the platform with the space station's orbit, a requirement when trying to hit a target moving at nearly 5 miles per second. An unplanned pause in the countdown for such missions immediately triggers a minimum 24-hour launch delay.
Tory Bruno, chief executive of United Launch Alliance, builder of the Atlas 5 rocket, said Saturday's problem involved one of three networked computer racks in a building at the base of the launch pad. Each rack features multiple systems, including identical circuit boards that work together as a “ground launch sequencer,” managing the final steps in a countdown.
The GLS computers manage events such as the retraction of the umbilicals and the firing of explosive bolts that release the rocket from the pad for liftoff, and all three have to be in perfect agreement for the countdown to begin.
During Saturday's launch attempt, the countdown reached T-minus 4 minutes and then entered a planned four-hour pause. When the countdown resumed four minutes before takeoff, one of the three GLS circuit boards took longer than expected to synchronize with the other two. That was enough to activate an automatic hold at the T-minus 3 minutes and 50 seconds mark.
Engineers planned to begin troubleshooting after draining the Atlas 5 of its liquid hydrogen and oxygen propellants and gaining access to the computer room. The decision on how to proceed depended on isolating the problem, replacing and testing any suspicious components.
The launch team, although disappointed, took the latest delay in stride.
“You know when you're playing and you get a bad call, you're a little irritated at first or a little frustrated at first, but you immediately focus on the next shot and that's what our teams do. “We are focused on the next launch,” said Mark Nappi, Boeing’s Starliner project manager.
“As soon as we got into the launch process and the launch turnaround, I looked into the control room and everyone had their heads down, working on procedures to prepare for another attempt tomorrow.”
Bruno said: “The disappointment lasts about three seconds. And then you immediately get to work and do your job. We'll be back.”
When it lifts off, the long-awaited flight will be the first piloted launch of an Atlas 5 and the first of the Atlas family of rockets since astronaut Gordon Cooper blasted off just a few miles away on the Mercury program's final flight 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 less expensive ship that has put 50 astronauts, cosmonauts and civilians into orbit on 13 flights, 12 of them to the space station. . since an initial pilot test flight in May 2020.
NASA funded the development of both spacecraft to ensure that the agency could send crews to the outpost even if one of the companies' ferry was grounded for any reason.
NASA, already years behind schedule due to budget shortfalls and a variety of technical problems that cost Boeing about $1.4 billion to correct, had hoped to launch the Starliner into orbit on May 6. But the launch was canceled when United Launch Alliance engineers detected problems with a pressure relief valve on the rocket's Centaur upper stage.
The Atlas 5 was taken off the pad and back to the ULA Vertical Integration Facility, where the Centaur valve was quickly replaced. But in the wake of the launch, Boeing engineers saw signs of a small helium leak in the Starliner's propulsion system.
The leak was traced to a flange on the pipeline that supplied pressurized helium to power a jet of the dedicated reaction control system in the Starliner's service module. The leak was characterized as “very small,” but engineers needed to demonstrate that it would not worsen dramatically in flight and cause problems for other boosters.
After extensive analysis and testing, mission managers concluded that the spacecraft could be launched safely as is, and said that even if the leak rate were 100 times worse than observed so far, it would not pose a risk to the crew nor for the mission. As it turned out, on Saturday the leak rate remained within acceptable limits.
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