Starliner Tests Still Underway, No Date for Butch and Suni’s Return

NASA and Boeing provided an update on the Starliner Crew Flight Test today. They are still conducting tests to determine why the Starliner commercial crew capsule experienced thruster failures and helium leaks on its way to the International Space Station last month. Starliner’s crew, NASA astronauts Butch Wilmore and Suni Williams, remain aboard the ISS. A date for their return still is not set.

At a news conference today, NASA Commercial Crew Program Manager Steve Stich and Boeing Vice President and Program Manager for Commercial Crew Mark Nappi explained the ground tests they’ve been conducting to determine why five of Starliner’s 28 Reaction Control System (RCS) thrusters stopped operating during the trip to the ISS. Four later came back online, but one will not be used again.

Starliner launched on June 5 and docked almost exactly one day later. Starliner can operate autonomously, but the crew can also take manual control. Butch and Suni did a number of manual maneuvers during the day-long trip as part of the test flight, firing the thrusters more often than necessary for a routine mission.

Boeing has been testing a similar thruster on the ground to see if that caused some condition that triggered software to “deselect” the thrusters. The leading theory is that they overheated because they were fired (“pulsed”) so many times and those at the aft end were facing the Sun during much of the journey. All five that went offline were in the aft end. Heat generated by the extra pulses plus the Sun may have been too much.

Boeing will conduct a “hot fire” test in space this weekend, firing the actual thrusters on Starliner. The main reason the mission has been extended far beyond the planned eight days is because the thrusters are in the capsule’s Service Module, which does not return to Earth. It separates from the Crew Module during descent and burns up in the atmosphere. Whatever tests Boeing wants to do with this specific Service Module must be done while it’s in space.

Boeing is also troubleshooting five helium leaks from manifolds associated with the thrusters. One was discovered before launch and determined not to be a showstopper. The others happened after it reached orbit.

On the ground, they’ve been inspecting a Starliner Service Module that was supposed to launch in 2021. It’s been filled with nitrogen tetroxide (NTO) for the past three years and they’ve now discovered “severe degradation” in some of the seals due to NTO vapors.

The manifolds on the Service Module that is docked to the ISS are closed while the thrusters are inactive so there are no leaks now, but NASA and Boeing will check the leak rates when they hot fire the thrusters this weekend to assess whether the are stable.

They haven’t decided whether the on-orbit tests will take place on Saturday or Sunday.

The bottom line is that more testing is needed both on the ground and in space so they still don’t know when Starliner will come home. Initially they said the capsule could only stay in space for 45 days because of battery limitations in the Crew Module, but now have decided that’s not a problem. A waiver was granted for Starliner to stay in space for 90 days, through early September.  “We’ll come home when we’re ready,” Stich asserted.

NASA and Boeing insist Starliner is safe enough to bring Butch and Suni home in an emergency at any time, but otherwise they want to continue doing the tests. Stich was asked repeatedly today if NASA was considering using a Crew Dragon to bring them home instead. His answer was that Starliner is the “prime option,” but declined to state definitively that’s what they’ll do. Nappi said Boeing is confident Starliner is safe to bring them back to Earth.

One factor in deciding when to bring Starliner home is to try to avoid interfering with the routine crew exchanges that take place on the ISS every six months. Four crew members come and go on U.S. Crew Dragons and three on Russian Soyuzes.

NASA is currently scheduled to swap Crew-8 with Crew-9 in mid-August and Roscosmos will launch Soyuz MS-26 on September 11 to replace Soyuz MS-25.

NASA prefers to have a 5-day handover between its crews, but there are only two docking ports on the U.S. segment. Right now Crew-8 is at one and Starliner at the other. Starliner would have to depart before Crew-9 launches to free up that port. If NASA and Boeing aren’t ready to bring Starliner home by the time Crew-9 needs to launch, they would have to bring Crew-8 down first to free that port instead and skip the handover. Stich said he’s working with NASA ISS Program Manager Dana Weigel on the timing, but they want the Crew 8/Crew 9 exchange to take place before the Soyuz crew change in September.

NASA will hold two news conferences tomorrow in preparation for Crew-9’s launch. The first is at noon EDT and Stich will be in front of the cameras again along with Weigel, Ken Bowersox, Associate Administrator for Space Operations, and SpaceX Director of Dragon Mission Management Sarah Walker. The second is at 2:00 pm EDT with the crew.

Another factor for when Crew-9 launches is the readiness of SpaceX’s Falcon 9 rocket, which suffered a rare failure on July 11. The first stage performed perfectly, but the second stage failed due to a liquid oxygen leak. The FAA regulates commercial space launches from a public safety standpoint and must grant approval for Falcon 9 to return to flight.

Tonight the FAA said it concluded no public safety issues were involved and SpaceX can resume launches when it’s ready.

SpaceX said it will launch as early as this Saturday.

The SpaceX team submitted our report to the FAA regarding Falcon 9’s launch anomaly, including likely cause and associated corrective actions → https://t.co/rg5Qiu5sKS

— SpaceX (@SpaceX) July 25, 2024

Thanks to the pace we’ve been able to launch, we’re able to gather unprecedented levels of flight data and are poised to rapidly return to flight as soon as Saturday, July 27 → https://t.co/DvO0z1NbUm

— SpaceX (@SpaceX) July 25, 2024