NASA continues to support Boeing as it tries to remedy a valve issue with its CST-100 Starliner, which will push the commercial crew vehicle’s operational missions back to 2023. Officials from NASA and Boeing delivered an update on the inquiry into the jammed valves in the Starliner’s propulsion system, which forced the cancellation of a launch effort in early August. As a result, the corporation was compelled to detach the spacecraft from the Atlas 5 launch vehicle and delay the Orbital Flight Test (OFT) 2 flight indefinitely.
Boeing officials substantially recapped their recent evaluation of the valve problem, including their conclusion that the primary cause was moisture interacting with nitrogen tetroxide (NTO) oxidizer infiltrating Teflon seals in the valves. This produced nitric acid, which corroded the valves and led them to become stuck closed.
Two of the spacecraft’s valves have been removed, and a third is in the process of being removed. Those valves will be sent to NASA’s Marshall Space Flight Center for a thorough examination, which will include CT scans. Other valves, like those on the Starliner, are being tested at NASA’s White Sands Testing Facility situated in New Mexico, which has dealt with hypergolic propellants before.
In a conference call with reporters, Michelle Parker, who serves as the vice president and the chief engineer in charge of the space and launch engineering at the Boeing company, said the moisture that connected with the NTO was likely “typical ambient humidity” in Florida.
Another aspect could have been the timeframe the NTO stayed in the spacecraft: 46 days compared to 35 days on the initial OFT mission, which had no valve issues. The vehicle, on the other hand, was designed to hold NTO for approximately 60 days before launch. “We felt we’d be alright,” said John Vollmer, Boeing’s vice president, and the program manager for commercial crew.
Boeing is already exploring possible remedies while the probe is ongoing. The valves’ core design is sound, according to Vollmer. “Are there any minor changes to the design that we need to make?” Is there anything else we should do to ensure we don’t receive any moisture?”
To prevent moisture from infiltrating the valves, technicians have applied desiccant to the vent holes surrounding the valves. According to Parker, Boeing is exploring installing heaters to the valves to prevent corrosion products from forming on the valves. That will be the subject of a design assessment in the following days.
The valves will be tested in White Sands in the same conditions that they were in Florida, such as high humidity, according to Steve Stich, who serves as the manager of the NASA commercial crew program. “We’ll try to replicate the identical scenario that a valve went through,” he said, monitoring the progression of corrosion and the difficulty of opening and closing the valve.