Boeing and NASA say the Starliner spacecraft is ready for an uncrewed flight, and a second uncrewed test mission for the spacecraft is now scheduled for May 19.
It’s been nine months since a standard pre-flight inspection of the spacecraft, then sitting atop a rocket on the launch pad in Florida, found that 13 of 24 oxidizer valves inside the Starliner propulsion system were stuck. The discovery was made within hours of takeoff.
Since then, engineers and technicians at Boeing and NASA have worked to understand exactly why the valves stopped and to fix the problem. They found that the dinitrogen tetroxide oxidizer loaded on the spacecraft 46 days before launch combined with the surrounding moisture to form nitric acid, which started the corrosion process inside the valve’s aluminum housing.
On Tuesday, during a conference call with reporters, officials from Boeing and NASA discussed the steps they have taken to mitigate the problem of Starliner’s upcoming test flight. The valves are still the same in the car, but technicians have closed the paths through which moisture may enter the propulsion system, said Michael Parker, vice president and deputy general manager of Boeing Space and Launch. They also extract moisture from the valves using nitrogen gas and load propellant onto the Starliner as launch approaches.
With these mitigations in place, the Starliner will soon be stacked on top of an Atlas V rocket built by United Launch Alliance. The Starliner was scheduled to be rolled out at the Atlas V launch complex in Florida on Wednesday, but Boeing said Operation paused due to hydraulic leakage in United Launch Alliance transmission vehicle.
So this is in line with Boeing’s on-and-off efforts to bring the Starliner into service. The company has been working on the vehicle since at least 2010, when it was called Crew Space Transportation-100, or CST-100. The Starliner made its maiden flight in December 2019, but problems arose just minutes after takeoff, when the spacecraft picked up the wrong “mission time lapse” from the Atlas V launch vehicle. It also had difficulty communicating with ground stations. NASA and Boeing flight controllers were able to restore communications with the Starliner and help it reach orbit. However, due to the fuel expended during these activities, Starliner was unable to complete its primary objective, demonstrating a safe docking with the International Space Station.
There were also problems during the flight back to Earth. Another software bug, discovered and fixed a few hours before the car returned to Earth through the atmosphere, would have caused the thrusters to fire at the Starliner service module the wrong way. The car was about to get lost a second time.
These problems led NASA to declare the first test flight of the Starliner a “high-definition close call” and begin a years-long investigation and deep dive into the problems of the Starliner program. Boeing agreed to pay for a second test flight at a cost of $410 million, and eventually prepared the Orbital Flight Test-2 mission, which arrived on the platform in the summer of 2021. After that, the car had a sticky valve problem. Finally, after all that, the company has Starliner back on the podium, ready to launch additional missions.
NASA, of course, currently has SpaceX’s Crew Dragon spacecraft to carry its astronauts to and from the International Space Station. The Crew Dragon has done five largely manned missions since mid-2020, but with tensions high between the United States and Russia, NASA would like it to have the option of moving a second crew to get to the station.
This means that there is great interest at NASA in the second Starliner test. Success on this test flight will likely lead to Boeing flying the crew to the space station for the first time as early as 2023.
“This is a really important step in our ongoing goal of having American transport capabilities to the International Space Station,” said NASA’s Cathy Luders, chief of human spaceflight operations. “Strong crew services are really important to our ongoing commitment to our research, science and technology development that we make on the International Space Station, and it is critical for us to achieve our exploration goals.”