Starliner is only days away from its first crewed launch however it’s running into a few complications. Earlier this month on the 8th was the spacecraft’s first launch attempt that was eventually scrubbed due to a valve problem not with the spacecraft but with the rocket. Fortunately for crews, while work was going on related to the Atlas V, an issue with Starliner was discovered.
This initially pushed the launch date back to an unknown date but has since been rescheduled for June 1st, in only a few days. The specific issue has to do with a helium leak in the reaction control system of Starliner. Interestingly, they might end up just leaving the leak and launching anyway. Here I will go more in-depth into the new launch date, the decision to leave the spacecraft as is, chances of more delays, and more.
Leave The Leak
When the leak within Starliner was discovered, teams began working to resolve the issue within the service module that was traced to a flange on a single reaction control system thruster. Helium is used in spacecraft thruster systems to allow the thrusters to fire and is not combustible or toxic. Around a week after the initial scrub and discovery of the additional helium leak, Boeing and NASA decided to conduct some tests. Specifically, as part of the testing, Boeing planned to bring the propulsion system up to flight pressurization just as it does prior to launch, and then in theory, allow the helium system to vent naturally to validate existing data and strengthen flight rationale.
They eventually conducted this test and said in a company statement, “Pressure testing performed on May 15 on the spacecraft’s helium system showed the leak in the flange is stable and would not pose a risk at that level during the flight. The testing also indicated the rest of the thruster system is sealed effectively across the entire service module. Boeing teams are working to develop operational procedures to ensure the system retains sufficient performance capability and appropriate redundancy during the flight. As that work proceeds, NASA’s Commercial Crew Program and the International Space Station Program will take the next few days to review the data and procedures to make a final determination before proceeding to flight countdown.”
While that statement sounds quite promising, comments directly from some officials paint somewhat of a different picture. Steve Stich, NASA commercial crew program manager, said engineers believe that a seal, a rubber ring about the size of a shirt button and the thickness of 10 sheets of paper, in the flange had a defect that grew worse during tests. He said other possibilities included an error installing the seal or foreign object debris that rubbed against the seal. Interestingly, NASA and Boeing concluded that Starliner can fly with the leak as-is. “If we were to remove the seal completely, the leak rate would not exceed our capability to manage that leak.” said Mark Nappi, Boeing vice president and commercial crew program manager. That made us comfortable that, if this leak were to get worse, it would be acceptable to fly” he said.
While they don’t seem too concerned, when the study of the helium leak was ongoing, Stich said engineers performed a review of the rest of the propulsion system just to make sure they didn’t have any other things that they should be concerned about. However, that review did actually turn up something he called a “design vulnerability” with Starliner’s propulsion system where, in a rare circumstance, the spacecraft would not be able to perform a deorbit burn if two adjacent “doghouses” that contain RCS and larger orbital maneuvering and attitude control (OMAC) thrusters failed. That failure, he said, would knock out enough OMAC and RCS thrusters to prevent existing backup plans for carrying out a deorbit burn from being implemented.
To solve this issue in a timely manner, engineers developed a different deorbit reentry mode that would alter the burns from the RCS. They highlighted that this outcome would be highly unlikely but something they want to prepare for just in case. Despite all these developments, the launch with two astronauts is still scheduled for June 1st. While its possible this gets pushed back further, it seems they are not interested in taking a large delay to disassemble and replace the necessary components. Some of the backup dates include June 2, June 5, and June 6.
Similar Problems
During a teleconference held recently, NASA and Boeing officials said that if the Starliner leak had happened in space, they would have found ways to deal with it there; they emphasized the leak was tiny and that hardware can fail unexpectedly even on fully certified spacecraft systems. “There’s no human-rated vehicle that doesn’t experience this kind of anomaly,” said Boeing’s Mark Nappi, they went on to mention SpaceX’s Dragon and even the Space Shuttle running into problems.
Looking more closely at the leak, it’s located in one of the Aerojet Rocketdyne reaction control system (RCS) thrusters that is located in a single “doghouse,” one of four such assemblies around the outside of Starliner’s service module. It is in a manifold that is used to open and close valves on each of the thrusters. The leak began at 7 pounds per square inch (psi) and has increased to between 50 psi and 70 psi. Still acceptable according to officials.
As far as the crew, they have been in quarantine for about a month, waiting through the delays, but are “in good spirits,” officials said. Wilmore and Williams remotely attended meetings and among other comments have urged the team to pace themselves, he said. (As military astronauts and former U.S. Navy test pilots, the CFT crew are also used to both long deployments as well as working on developmental programs like Starliner, where schedule changes like this are common.) They just arrived in Florida yesterday for the soon-to-be launch.
Focusing back on the leak, it brings up questions regarding its late discovery and why it wasn’t found earlier, unfortunately for Starliner, it’s experienced similar problems in the past. During the second uncrewed orbital flight test for example, issues were detected with 13 propulsion-system valves in the spacecraft prior to launch. The spacecraft had already been mated to its launch rocket, ULA’s Atlas V, and taken to the launchpad. Attempts to fix the problem while on the launchpad failed, and the rocket was returned to the ULA’s VIF (Vertical Integration Facility). Attempts to fix the problem at the VIF also failed, and Boeing decided to return the spacecraft to the factory, thus canceling the launch at that launch window. There was a commercial dispute between Boeing and Aerojet Rocketdyne over responsibility for fixing the problem. The valves had been corroded by intrusion of moisture, which interacted with the propellant, but the source of the moisture was not apparent. By late September 2021, Boeing had not determined the root cause of the problem, and the flight was delayed indefinitely.
This is a process that Boeing definitely wants to try and avoid this time around. That being said, there are other factors influencing the launch date and future delays. For example, the Atlas V rocket has some parts that would expire in June and July, said ULA’s Gary Wentz, who is vice president of government and commercial programs. Other launches may also have to shift around if the delay persists. Also, CFT is only allowed to dock at a single port of the Harmony module of the ISS, but “we’re pretty flexible all through the summer” if Starliner needs to hold, said the ISS program manager.
To put things in perspective, this first crewed Starliner flight was originally scheduled for 2017, around 7 years ago. Frequent delays and problems have halted progress and stopped Boeing from receiving billions in possible crew contracts. The recent helium leak problem is just another issue in a long list. In the months leading up to this initial attempt, the company, alongside NASA were working on a few issues that came up related to flammable tape used inside the spacecraft and its parachute safety margin. Those were eventually fixed but highlight the pattern that Starliner has been stuck in.
Assuming the launch does go through in a few days, we can expect a similar flight profile to Starliner’s previous uncrewed flight test. In a recent briefing, Nappi highlighted, “The CFT flight is really the introduction of crew into our vehicle systems, so a lot of our flight test objectives are about how that interface will work. It’s all about, does the vehicle perform with the human in the loop as expected” he said. Some of the test objectives range from the performance of the spacecraft’s life support systems to the use of manual controls to operate the spacecraft should automated systems fail. They pointed out that the two pilots, Wilmore and Williams will test the ability to manually control and orient the spacecraft during a day-long flight to the ISS, and test maneuvering during a 6.5-hour trip from the station back to the ground. The goal is a successful launch and finally the certification of Starliner. This would allow them to carry on with the first official Starliner crewed mission named Starliner 1 sometime in 2025.
Conclusion
Starliner was about to launch crew until a helium leak was discovered within a Reaction Control System Thruster. Teams don’t seem too concerned however and have decided to likely go through with the launch in only a few days. We will have to wait and see how it progresses and the impact it has on the space industry.