NASA orders more tests on Starliner, but says crew isn’t stranded in space

NASA and Boeing officials pushed back Friday on headlines that the commercial Starliner crew capsule is stranded at the International Space Station but said they need more time to analyze data before formally clearing the spacecraft for undocking and reentry.

Two NASA astronauts, commander Butch Wilmore and pilot Suni Williams, will spend at least a few more weeks on the space station as engineers on the ground conduct thruster tests to better understand issues with the Starliner propulsion system in orbit. Wilmore and Williams launched June 5 aboard an Atlas V rocket and docked at the station the next day, completing the first segment of Starliner's first test flight with astronauts.

NASA managers originally planned for the Starliner spacecraft to remain docked at the space station for at least eight days, although they left open the possibility of a mission extension. The test flight is now likely to last at least a month and a half, and perhaps longer, as engineers wrestle with helium leaks and thruster glitches on Starliner's service module.

Batteries on this Starliner spacecraft were initially only certified for a 45-day mission duration, but NASA officials said they are looking at extending the limit after confirming the batteries are functioning well.

“We have the luxury of time," said Ken Bowersox, associate administrator for NASA's space operations mission directorate. “We’re still in the middle of a test mission. We’re still pressing forward."

Previously, NASA and Boeing officials delayed Starliner's reentry and landing from mid-June, then from June 26, and now they have bypassed a potential landing opportunity in early July. Last week, NASA said in a statement that the agency's top leadership will meet to formally review the readiness of Starliner for reentry, something that wasn't part of the original plan.

“We’re not stuck on ISS”

Steve Stich, manager of NASA's commercial crew program, said Friday that he wanted to clear up "misunderstandings" that led to headlines claiming the Starliner spacecraft was stuck or stranded at the space station.

“I want to make it very clear that Butch and Suni are not stranded in space," Stich said. "Our plan is to continue to return them on Starliner and return them home at the right time. We have a little bit more work to do to get there for the final return, but they're safe on (the) space station."

With Starliner docked, the space station currently hosts three different crew spacecraft, including SpaceX's Crew Dragon and Russia's Soyuz. There are no serious plans under consideration to bring Wilmore and Williams home on a different spacecraft.

"Obviously, we have the luxury of having multiple vehicles, and we work contingency plans for lots of different cases, but right now, we’re really focused on returning Butch and Suni on Starliner," Stich said.

"We're not stuck on the ISS," said Mark Nappi, Boeing's vice president in charge of the Starliner program. "It's pretty painful to read the things that are out there. We've gotten a really good test flight that's been accomplished so far, and it's being viewed rather negatively.”

Stich said NASA officials should have "more frequent interaction" with reporters to fill in gaps of information on the Starliner test flight. NASA's written updates are not always timely, and often lack details and context.

NASA officials have cleared the Starliner spacecraft for an emergency return to Earth if astronauts need to evacuate the space station for safety or medical reasons. But NASA hasn't yet approved Starliner for reentry and landing under "nominal" conditions.

"When it is a contingency situation, we’re ready to put the crew on the spacecraft and bring them home as a lifeboat," Bowersox said. “For the nominal entry, we want to look at the data more before we make the final call to put the crew aboard the vehicle, and it's a serious enough call that we’ll bring the senior management team together (for approval)."

Stich said the primary reason for keeping the spacecraft at the station for the next few weeks is to give engineers time to test a Starliner thruster on the ground. As it approached the station earlier this month, the craft's control software deemed five of Starliner's 28 reaction control system thrusters unusable.

Four of these five control jets, made by Aerojet Rocketdyne, successfully fired during a test while docked to the station on June 15 and are cleared for use for the rest of the mission. But engineers can't be certain the small rocket engines fired at full thrust because of limitations while docked at the space station. They also have more work to do to determine why these five thrusters ran into problems in the first place.

So engineers will take an identical thruster on the ground and test-fire it at a NASA facility in New Mexico. The test will simulate the exact sequence of firings Starliner's thrusters performed as it approached the space station and the firing sequence engineers expect when Starliner undocks and returns to Earth.

The test will take a couple of weeks, then engineers will inspect the thruster. "The test will help us understand the thruster performance," Stich said. "It may give us 100 percent confidence that everything we’ve seen on orbit is fine. It’s just one more piece of data that we can have before we actually de-orbit the vehicle.”

At the end of the mission, Starliner's service module will detach before reentry and burn up, while the crew module parachutes to an airbag-cushioned landing, likely at White Sands, New Mexico. Officials are eager to gather as much data on thruster performance as possible in flight because they won't have an opportunity to inspect the service module after landing.

NASA astronauts Butch Wilmore and Suni Williams aboard the International Space Station.

Credit: NASA

Depending on what they find after the testing, NASA and Boeing officials may decide to test-fire Starliner's thrusters again in orbit or adjust the sequence of thruster firings after the spacecraft leaves the space station to head for reentry. Even if managers decide they don't need to change anything with the Starliner spacecraft currently in orbit, data from the upcoming ground test should help nail down the root cause of the problem.

“Once that testing is done, then we'll look at the plan for landing," Stich said. "We don't have a targeted date today."

Boeing's Starliner spacecraft encountered similar thruster issues on an unpiloted test flight in 2022, and engineers thought software corrections would resolve the problem. "We clearly missed something," Stich said. "We clearly have an integrated effect between how we’re executing the rendezvous profile and how we’re using the thrusters, so I think we learned something there.”

NASA and Boeing cleared Starliner for launch earlier this month despite knowing the spacecraft had a small helium leak. The spacecraft uses helium to pressurize the service module's propulsion system when in transit to and from the space station.

Ground controllers discovered four more small helium leaks during Starliner's flight up to the station. Stich said engineers continue to test seals on the ground to determine what caused the leaks, but ground teams have closed valves to isolate the helium system while Starliner is attached to the space station, so leaks have temporarily stopped.

The valves will reopen for the flight back to Earth, but Stich said Starliner has 10 times the amount of helium it needs to complete the return trip.

Nappi said engineers are confident Starliner is safe to bring Wilmore and Williams home.

“We understand these issues for a safe return, but we don't understand these issues enough yet to fix them permanently," he said. "And the only way that we can do that is to take the time in this unique environment and get more data, run more tests."

Once the Starliner spacecraft is back on the ground, NASA and Boeing plan to certify the crew capsule for operational long-duration flights. At that time, Starliner will join SpaceX's Crew Dragon spacecraft as one of two US human-rated spaceships ferrying astronauts to and from the space station.

NASA is still holding open the possibility for Boeing to launch the first operational Starliner flight to the space station in February. However, engineers must resolve the thruster issues and helium leaks before the next mission, and it appears likely NASA will tap SpaceX to take the February launch slot, pushing the first of Boeing's six operational missions until the second half of 2025.