Boeing continues Starliner valve troubleshooting

Boeing’s Starliner spacecraft inside the Vertical Integration Facility at Cape Canaveral Space Force Station. Credit: Boeing

Boeing engineers at Cape Canaveral continue troubleshooting stuck valves in the propulsion system of the company’s Starliner crew capsule in hopes of resolving the problem — and understanding what caused it — in time to take off on an unpiloted test flight before the current launch window closes later this month.

Mission managers called off a launch attempt Aug. 3 after 13 of 24 valves inside the Starliner spacecraft’s propulsion system did not open as expected during pre-flight testing.

The commercial crew capsule was poised to head into orbit on top of a United Launch Alliance Atlas 5 rocket on a five-day test flight to the International Space Station. The mission — called Orbital Flight Test-2 — is a do-over of a problem-plagued test flight in 2019 that failed to reach the space station due to software errors.

If Boeing’s second shot at the unpiloted test flight goes well, it will pave the way for the next Starliner mission to carry three astronauts to the space station.

Ground teams rolled the Atlas 5 rocket back into ULA’s Vertical Integration Facility last week, allowing Boeing workers to begin hands-on inspections of the Starliner propulsion system.

Boeing said Monday it restored functionality to seven of the 13 stuck valves over the weekend, but work continues on the remaining valves. Engineers are also investigating what caused the valves to stop working.

Engineers noticed the valves were misbehaving after a lightning storm that passed over the launch pad before last week’s launch attempt. Boeing previously said the severe weather appears to be an unlikely cause for the problem.

Teams inside the VIF have inspected the spacecraft’s “doghouse” propulsion pods for water or electrical damage. Boeing said the physical inspections and chemical sampling has so far not revealed any signs of damage or corrosion.

“Test teams are now applying mechanical, electrical and thermal techniques to prompt the valves open,” Boeing said in a statement.

The troubleshooting includes applying power directly to the valves, rather than routing commands through the spacecraft’s electrical system.

The propulsion system valves in question are inside the Starliner’s service module, which has an array of rocket thrusters made by Aerojet Rocketdyne that are designed to propel the spacecraft away from its launcher during an in-flight emergency. Other thrusters on the service module are used for in-orbit maneuvers and spacecraft pointing control.

“Boeing is working a systematic plan to open the affected valves, demonstrate repeatable system performance, and verify the root cause of the issue before returning Starliner to the launch pad for its Orbital Flight Test-2 mission,” the company said in a statement.

Boeing said it is assessing “multiple launch opportunities” for the Starliner test flight later this month. If the OFT-2 mission isn’t off the ground by late August, the test flight could be delayed several months, and the Starliner will be returned to Boeing’s factory at the nearby Kennedy Space Center for further troubleshooting.

ULA has already taken measures to protect for the possibility that the Starliner’s Atlas 5 rocket might have to be disassembled to allow the company to move on to other missions on its launch schedule. Before rolling the Atlas 5 back into the hangar, ULA drained the first stage’s fuel tank of kerosene.

A SpaceX Cargo Dragon capsule is set for launch Aug. 28, and it will use the same docking port needed by the Starliner spacecraft. The Dragon spaceship will occupy the space station docking port until late September.

NASA’s robotic Lucy asteroid science probe is scheduled for liftoff during a 23-day planetary launch period opening Oct. 16. Like the Starliner mission, Lucy will use a United Launch Alliance Atlas 5 rocket launched from Cape Canaveral to depart Earth and head into the solar system for encounters with eight asteroids, a record number for a single mission.

The schedule of visiting vehicle traffic at the space station, and the high-priority launch of the Lucy asteroid mission will limit launch opportunities for the Starliner mission from late August until November.

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Follow Stephen Clark on Twitter: @StephenClark1.