In early August, the CST-100 Starliner was just hours from taking off on its second uncrewed flight test when jammed valves in the spacecraft’s propulsion system prompted a launch scrub which has turned into a year-long delay.
In a recent interview, John Vollmer, who works as the vice president as well as program manager of Boeing’s commercial crew program, stated of the delay, “It was a terrible pill to swallow.” The business had been working for a year and a half to fix software issues that had caused the first uncrewed flight test, known as Orbital Flight Test (OFT), to be canceled in December 2019.
“We had put the software through a lot of testing.” That was something we’d become used to. “It hurt a little because it wasn’t anything we expected,” he explained.
Boeing is still looking into why 13 valves were stuck in the closed position. The most likely cause is that leaked nitrogen tetroxide (NTO) propellant combined with moisture to produce nitric oxide, which corroded the valve.
“We’ve created a large fault tree to be able to go through and check at every possibility,” he said. “We’re almost 75% of the way through that fault tree.” “We’re ticking the boxes off.”
The inquiry is being carried out by a team consisting of NASA, Aerojet Rocketdyne, which offers the Starliner’s propulsion system, and Marotta, which manufactures the valves for that system.
The next phase in the inquiry will be to remove many of the spacecraft’s valves for further examination. According to Michelle Parker, who works as the vice president and the chief engineer in charge of the space and launch engineering at Boeing, the valves will be transferred to NASA’s Marshall Space Flight Center for the CT scans and other tests.
One of the most pressing questions is why the corrosion appeared on this spaceship when it was not visible during the first uncrewed flight test or other ground tests. “That’s something we’ve been looking at closely,” she said. “These are the exact valves, with the same part numbers, that we used in our service module hot-fire, pad abort assessment in New Mexico, and OFT-1.” Those valves haven’t changed in any way.”
The business is looking at the variations between OFT-1 and OFT-2, such as how long this NTO propellant remained in the spacecraft’s tanks before launch, as well as humidity, which could have contributed to the moisture that reacted with the NTO.
The fact that the spaceship for OFT-2 was first utilized for a set of environmental tests termed Environmental Qualification Testing (EQT) has been ruled out by the corporation. Parker stated, “We’ve done a bunch of tasks to exonerate EQT.” Some valves, for example, were replaced as a result of the examinations. “Even valves that were newer, non-EQT valves had this problem.”