The apparently star-crossed one Boeing Starliner — within minutes of the long-delayed explosion during 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 encountered a problem, causing a nuisance -minute scrub caused.
Initially, engineers were told to attempt another launch at 12:03 a.m. EDT on Sunday, assuming the problem could be resolved in time. But NASA later announced that the team would forgo a Sunday launch to give engineers more time to assess the computer problem.
The Starliner’s test flight includes a rendezvous and docking with the International Space Station. Based 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 would give.
The Starliner’s crew, Commander Barry “Butch” Wilmore and co-pilot Sunita Williams, arrived on May 6 within about two hours of launch, but were derailed by problems. with a pressure relief valve in their Atlas 5 rocket, and a helium leak in the capsule’s propulsion module.
Those issues were resolved, and after a few minor issues on Saturday, the countdown seemed to be going smoothly toward a scheduled launch at 12:25 p.m. EDT. But 10 seconds after the countdown came out of a scheduled break at the T-minus 4-minute mark, the clocks suddenly stopped ticking.
Launches to the International Space Station are timed when Earth’s rotation aligns the pad with the space station’s orbit, a requirement when trying to reach a target moving at nearly 5 miles per second. An unplanned interruption to the countdown for such missions will immediately result in a launch delay of at least 24 hours.
NASA
Tory Bruno, CEO of United Launch Alliance, builder of the Atlas 5 rocket, said the issue Saturday 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 of the countdown.
The GLS computers manage events such as retracting the umbilical cords and firing explosive arrows that free the rocket from the launch pad, and all three must be in perfect agreement before the countdown can take place.
During Saturday’s launch attempt, the countdown ticked down to T-minus 4 minutes and then entered a scheduled four-hour hold. When the countdown resumed four minutes before the explosion, it took longer than expected to synchronize one of the three GLS circuit boards with the other two. That was enough to trigger an automatic hold at the T minus 3 minutes and 50 seconds.
NASA
Engineers planned to begin troubleshooting after draining the Atlas 5’s liquid hydrogen and oxygen propellants and gaining access to the computer room. A decision on how to proceed depended on isolating the problem and replacing and testing any suspect components.
Although disappointed, the launch team handled the latest delay.
“You know when you’re playing a match and you get a bad decision, you’re a little annoyed at first, you’re a little frustrated at first, but you immediately focus on the next ball and that’s what our teams do. We are focused on the next pitch,” said Mark Nappi, Boeing’s Starliner project manager.
“As soon as we went into the launch scrub and launch turnaround, I looked over at the control room and everyone was sitting with their heads down working on procedures to get ready for another attempt tomorrow.”
Bruno said: “The disappointment lasts about three seconds. And then you go straight to work and do your job. We’ll be back.”
Whenever it lifts off, the highly anticipated flight will be the first piloted launch of an Atlas 5, and the first for the Atlas family of rockets since astronaut Gordon Cooper took 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, lower-cost spacecraft that has carried 50 astronauts, cosmonauts and civilians into orbit in 13 flights, 12 of which to the space station. since a first piloted test flight in May 2020.
NASA funded the development of both spacecraft to ensure that the agency could launch crews to the outpost even if a company’s ferry ship were grounded for whatever reason.
NASA had been behind schedule for years due to budget shortfalls and a variety of technical problems that cost Boeing about $1.4 billion to correct. NASA had hoped to put the Starliner into orbit on May 6. But the launch was scrapped when United Launch Alliance engineers discovered problems with a pressure relief valve in the rocket’s Centaur upper stage.
The Atlas 5 was towed off the platform and back to ULA’s Vertical Integration Facility, where the Centaur valve was quickly replaced. But in the aftermath of the launch operation, Boeing engineers saw signs of a small helium leak in the Starliner’s propulsion system.
The leak was traced to a flange in the pipes that supplied pressurized helium to power a specific reaction control system jet in the Starliner’s service module. The leak was characterized as “very minor”, but engineers had to demonstrate that it would not drastically worsen during flight and cause problems for other thrusters.
After extensive analysis and testing, mission managers concluded that the spacecraft could be safely launched as is, saying that even if the leak rate were a hundred times worse than previously observed, it would pose no risk to the crew or the mission. It turned out that the leak rate on Saturday remained within acceptable limits.