Published: Wednesday, 20 October 2021 06:35
Boeing's CST-100 Starliner will reach the ISS a little more than a day after its scheduled Dec. 20 launch from Cape Canaveral, Florida. Credit: Boeing
WASHINGTON — NASA continues to stand behind Boeing as the company works to resolve a valve problem with its CST-100 Starliner that will push back operational missions of the commercial crew vehicle into 2023.
NASA and Boeing officials provided an update Oct. 19 on the investigation into the stuck valves in the Starliner’s propulsion system that scrubbed a launch attempt in early August. That eventually forced the company to remove the spacecraft from its Atlas 5 launch vehicle and postpone the launch of the Orbital Flight Test (OFT) 2 indefinitely.
Boeing officials largely recapped their recent assessment of the valve issue, including their belief the leading cause was that nitrogen tetroxide (NTO) oxidizer, permeating Teflon seals in the valves, interacted with moisture on the other side. That created nitric acid that corroded the valves and caused them to stick in the closed position.
Technicians have removed two of the valves from the spacecraft and are working on removing a third valve. Those valves will go to NASA’s Marshall Space Flight Center for detailed studies, including CT scans. Other valves like those on Starliner are being tested at NASA’s White Sands Testing Facility in New Mexico, which has experience dealing with hypergolic propellants.
The moisture that interacted with the NTO was likely “normal environment humidity” in Florida, said Michelle Parker, vice president and chief engineer of space and launch engineering at Boeing, in a call with reporters.
Another factor may have been the length of time the NTO was in the spacecraft: 46 days, versus 35 days on the original OFT mission, which had no valve problems. However, the vehicle was designed to store NTO for up to 60 days before launch. “We thought we’d be fine,” said John Vollmer, vice president and program manager of the commercial crew program at Boeing.
While the investigation is ongoing, Boeing is already looking into potential solutions. “The basic design is sound,” Vollmer said of the valves. “Are there some slight modifications we need to make to the design? Is there additional purging that we need to do to make sure we don’t get moisture?”
Technicians have added desiccant to vent holes near the valves to keep moisture from reaching the valves. Parker said Boeing is also considering adding heaters to the valves that would free up any corrosion products that do form on the valves. A design review for that is scheduled for the coming days.
Steve Stich, NASA commercial crew program manager, said tests at White Sands will expose the valves to the same conditions they saw in Florida, including high humidity. “We’ll try to recreate the exact scenario a valve went through,” he said, measuring how the corrosion grows and how difficult it becomes to open and close the valve.
As in a recent interview, Boeing executives said they were looking for launch opportunities in the first half of 2022 for OFT-2. An exact date will depend on the progress made in the investigation and repairs to the spacecraft, as well as launch vehicle availability and when docking ports on the International Space Station will be open.
If OFT-2 does fly by the middle of next year, it’s possible that Boeing could follow up with the first crewed flight, the Crew Flight Test (CFT), before the end of next year. “We like to see six months between flights,” Vollmer said, to cover the turnaround time between missions. “We are aggressively working the CFT vehicle in parallel” to the investigation.
The Starliner problems put Boeing far behind SpaceX, the other commercial crew company. SpaceX is set to launch its third operational Crew Dragon mission for NASA, Crew-3, Oct. 31. It will fly the Crew-4 and Crew-5 missions in 2022.
The series of consecutive SpaceX missions means that company is approaching the end of its original contract with NASA, which included six operational or “post-certification” missions. With the station expected to operate through the end of the decade, Stich said that NASA was starting the process to add additional flights to those contracts.
Once Boeing does complete its test flights and is certified for crew rotation missions, he said NASA will likely alternate between the two companies. “When we get into the long-term rotations, we would like to see SpaceX fly once a year and then Boeing fly one a year as well,” he said.
Stich also reiterated his confidence that Starliner will get past its problems. “We have every confidence that Boeing will be flying crew soon,” he said. “I have no reason to believe that Boeing won’t be successful.”
Boeing, which took a $410 million charge against earnings in January 2020 to pay for OFT-2, has not disclosed how much it’s spent on the mission, including the repairs. Vollmer confirmed that Boeing is covering the full cost of the work to investigate and repair Starliner. “NASA would not bear any responsibility for those costs,” he said.
He declined to say how this work affected Boeing’s ability to make any profit on the program. “I will say we are 100% committed to fulfilling our contract with the government. We intend to do that.”
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