No decision has been made yet, but NASA detailed Wednesday an option to get Boeing’s Starliner astronauts home on a SpaceX Crew Dragon if needed.

NASA’s Butch Wilmore and Suni Williams ar+rived on Starliner on June 6 a day after launching from Cape Canaveral on the Crew Flight Test mission for what was supposed to be about an eight-day stay on the International Space Station.

Issues with thrusters and helium leaks on Starliner’s propulsion module, though, led Boeing and NASA to try to figure out if it would be safe enough to fly home with humans on board — going through a series of ground tests and on-station hot fires — but the exact problem has yet to be nailed down.

“When we started this mission, it was a test mission. We knew that it potentially had a higher risk than a flight on a vehicle that has more experience, more flights on it,” NASA’s Ken Bowersox, associate administrator of the Space Operations Mission Directorate, said during a press conference. “So we’re at the point now where we see additional risk.”

Bowersox added “our chances of an uncrewed Starliner return has increased a little bit based on where things have gone over the last week or two and that’s why we’re looking more closely at that option to make sure that we can handle it.”

But new data or new analysis could make it shift back, he said.

The primary backup plan if Starliner comes home without Williams and Wilmore would be to send up the SpaceX Crew-9 mission, now set for no earlier than Sept. 24, with only two of its four planned crew members on board the Crew Dragon Freedom.

The Starliner’s duo would then stay on board the ISS and officially join Expedition 72 and only fly home in February when SpaceX’s Crew-10 mission is slated to arrive. NASA has not said which of the four Crew-9 members would have to stay behind. Currently assigned are NASA astronauts Zena Cardman, Nick Hague and Stephanie Wilson along with Roscomos cosmonaut Aleksandr Gorbunov.

“We haven’t made a decision yet of whether we pursue the rest of the mission and completed nominally … or we have Starliner come home in an uncrewed configuration,” NASA Commercial Crew Program Manager Steve Stich said. “So that’s the decision ahead of us. Knowing both Butch and Suni, they are professional astronauts and test pilots and they understand the difficulties of the decisions that were faced. They have complete confidence in the ground teams and and then they’ll do what we need them to do.”

Stich said Williams and Wilmore were already prepared as test pilots to potentially have to join the ISS crew for a long stay in case Starliner had issues during the flight. NASA has always built-in contingency to its mission plans, he said. Other contingency options have been to send home SpaceX flights with one or two extra passengers home. That’s something NASA and SpaceX already tested out in case Russia’s Soyuz spacecraft had issues like it did when NASA astronaut Frank Rubio had to remain on board the ISS for a year instead of six months from 2022-2023.

Bowersox alluded to disagreement within NASA’s ranks and Boeing over the risk posed to Starliner and its astronauts.

“It’s been really great to watch our team working — our Boeing team, our NASA team — the way people are speaking up, the way we’re hearing different voices, different thoughts on how critical different factors are in the decision,” Bowersox said. “I think it’s been very healthy. I have to admit that sometimes when we get disagreement, it’s not fun. It can be painful having those discussions, but it’s what makes us a good organization.

“And it’s what will get us to a good decision as we approach that point here in the future. And I don’t think we’re too far away from making that call.”

NASA has authorized Boeing to lay out the plan for what would be required to do that uncrewed undock, but won’t get a look at that schedule until next week, Stich said. He said a decision by mid-August should be made about when the undock opportunities would fall with landing options starting Sept. 2 and then about every four days.

Starliner would have to undock before Crew-9 could arrive as the ISS has only two ports that can handle either Starliner or Dragon spacecraft docking.

One of the limits to an uncrewed undocking is Starliner’s software, which would need some updating to configure some software parameters. Starliner was able to undock without crew in 2022 during the OFT-2 mission. The time to change those parameters, though, isn’t a quick fix, Stich said, and changes would have to be run through some test cases “if we were to pivot to an uncrewed undock.”

Boeing last week posted that its series of tests support flight rationale to send Starliner home as planned with astronauts on board. The company is trying to play catchup to SpaceX and be able to begin its contract to fly six regular Starliner missions on crew rotation to the ISS under the Commercial Crew Program.

NASA’s Bowersox said Boeing cites its knowledge of their hardware and the sheer number of tests performed, and have run up against those in NASA he called more conservative since there is the more-trusted SpaceX option to bring its astronauts home.

No Boeing representative was present during the press conference.

The views on just what the root cause is and the physics of the deorbit burn needs of the thrusters and helium leaks are the items holding up the decision.

“We could take either path and reasonable people could pick either path, depending on where their view is on our position in the uncertainty band that we have for the data that we’ve got on the thruster system on the propulsion system,” Bowersox said. “So moving forward, what we’re trying to do is reduce that uncertainty, see if we can drive some more consensus amongst our team. At the same time, getting more serious about evaluating our other options.”