With no consensus on the safety of the Starliner crew capsule, NASA officials said Wednesday they need another week or two before deciding whether to bring two astronauts back to Earth on Boeing's spacecraft or extend their stay on the International Space Station until next year.
Boeing's Starliner spacecraft, stricken by suspect thrusters and helium leaks, is taking up a valuable parking spot at the space station. It needs to depart the orbiting research complex, with or without its two-person crew, before the launch of SpaceX's next Dragon crew mission to the station, scheduled for September 24.
"We can juggle things and make things work if we need to extend, but it’s getting a lot harder," said Ken Bowersox, associate administrator of NASA's spaceflight operations directorate. "With the consumables we’re using, with the need for the use of the ports for cargo missions, those types of things, we’re reaching a point where that last week in August, we really should be making a call, if not sooner.”
Last week, NASA officials said they expected to make a decision in mid-August—presumably this week—but Bowersox said Wednesday NASA probably won't make the final call on what to do with the Starliner spacecraft until the end of next week, or the beginning of the week of August 26.
“We’ve got time available before we bring Starliner home and we want to use that time wisely," Bowersox said.
NASA astronauts Butch Wilmore and Suni Williams launched inside Boeing's Starliner spacecraft on June 5. Their mission is the first crew test flight on Boeing's capsule before NASA clears Starliner for regular crew rotation flights to the space station. But after software setbacks, parachute concerns, and previous problems with its propulsion system, Boeing's Starliner program is running more than four years behind SpaceX's Dragon crew spacecraft, which flew astronauts to the station for the first time in 2020.
And now, there's a significant chance the Starliner crew won't come home in the spacecraft they launched in. Bowersox, a former astronaut, said NASA brought in propulsion experts from other programs to take a fresh look at the thruster issue.
Engineers are still investigating the root cause of why five of Starliner's 28 reaction control system thrusters, supplied by Aerojet Rocketdyne, failed during approach to the space station the day after launch. The thrusters overheated as they pulsed over and over again to fine-tune the ship's rendezvous with the station. Tests of a similar control jet on the ground suggested a Teflon seal in an internal valve could swell at higher temperatures, restricting the flow of propellant to the thruster.
Four of the five thrusters that failed before Starliner docked at the station have recovered and generated near-normal thrust levels during test-firings last month. But many engineers at NASA aren't convinced the thrusters will work normally on Starliner's journey from the space station back to Earth. These control jets are needed to keep the spacecraft pointed in the right direction when four larger rocket engines fire for the deorbit burn to steer the capsule on a trajectory back into the atmosphere for landing.
Rapid pulses of the thrusters, coupled with a long firing of the four larger engines, could raise temperatures inside four doghouse-shaped propulsion pods around the perimeter of Starliner's service module. Once the deorbit burn is complete, Starliner will jettison the service module to burn up in the atmosphere, and its crew module will use a different set of thrusters to guide its reentry. Then, it will deploy parachutes to slow for landing, likely at White Sands, New Mexico.
Elevated Risk
Bowersox said the outside engineers brought in from other NASA centers have, so far, largely agreed with the assessments made by the team working full time on Starliner.
“There are a lot of folks out there that have worked with similar thrusters, and have seen similar issues,” he said. “So we’ve gotten feedback on what we’re seeing, and a lot of it is confirming what we thought was causing the signatures that we were observing on orbit. It’s really tough when you don’t have the actual hardware to look at, when it’s up in space.”
If NASA decides to bring Wilmore and Williams home on Starliner, Bowersox said the agency will have to accept more risk than officials originally expected. NASA officials were unable to quantify how much additional risk the thruster problem might pose to the astronauts if they rode back to Earth inside the spacecraft.
"It’s really taken some time to work through this and getting experts together, because we don’t have enough insight and data to make some sort of simple black-and-white calculation that says this is what you should do or not do," said Russ DeLoach, chief of NASA's office of safety and mission assurance. "I think that’s why we bring a series of experts in from different backgrounds. [It] gives us different perspectives. That means there are different opinions. There is a lot of engineering judgement that goes into this."
On August 2, Boeing said it "remains confident in the Starliner spacecraft and its ability to return safely with crew." NASA officials haven't expressed the same confidence.
At a so-called Program Control Board meeting earlier this month, NASA managers asked representatives of various teams involved on the Starliner program whether they were ready to give the green light for Boeing's spacecraft to return to Earth with its two-person crew. Many of the board members said no, prompting NASA to postpone a meeting of senior agency officials in a flight readiness review that would have decided on a formal "go" or "no go" for Starliner's voyage home.
"I will tell you how I took the question that I heard," DeLoach said. "It really was, 'Do you feel like you have all the data you would need now to make a good decision?' To me, most people were at no, we need a little more work, and that’s why we’re continuing to work it. There were a few people that seemed to already be there (at a yes)."
Bowersox said engineers will attempt to model the behavior of the valve with the bulging Teflon seal over the next week and its effects on thruster performance. Managers will evaluate the modeling data, along with other test results, at another Program Control Board meeting as soon as next week. Then, NASA leadership will convene a flight readiness review chaired by Bowersox. If there's no consensus out of that review, the final decision could go to NASA's most senior civil servant, Jim Free, or NASA administrator Bill Nelson.
There is some level of risk with extending the stay of Wilmore and Williams on the International Space Station and returning them to Earth on a SpaceX Crew Dragon spacecraft early next year. If that happens, the astronauts will spend eight months or more in orbit, and things can go wrong during spaceflight. Their original flight plan called for an eight-day stay at the outpost.
If NASA opts to undock Starliner from the space station without the astronauts aboard, there will be a short period of time when the only way for Wilmore and Williams to come home is on the SpaceX Dragon spacecraft currently parked at the station. In that case, the Dragon capsule would have to reenter the atmosphere with a crew of six, as opposed to the normal complement of four astronauts. Wilmore and Williams would not wear pressure suits for the trip back to Earth.
If this is how NASA proceeds, two SpaceX-made launch-and-entry spacesuits for Wilmore and Williams would launch on the following Dragon mission in late September. This Dragon spacecraft would launch with a crew of two, rather than four, for a five- or six-month expedition, leaving empty seats for the Starliner astronauts to occupy when it comes back to Earth next year.
"The challenge in this situation is the alternative plan raises risk, we’ve got increased risk on the baseline plan, and we always knew that a test flight potentially was a bit higher risk than return with a vehicle that has a lot of flights under its belt," Bowersox said.
Wilmore and Williams haven't spoken with reporters since July 10. Joe Acaba, chief of NASA's astronaut corps, said Wednesday the Starliner astronauts were aware of the risks and uncertainties associated with a test flight of a new spacecraft.
"I’ve spoken quite a bit with Butch and Suni," Acaba said. "They are receiving a lot of information that we are reviewing here on the ground. I do ask for their opinion, but when I talk to them, they are relying on us on the ground to analyze the data and to come up with a decision. And they will do what we ask them to do, and that’s their job as astronauts."
Both astronauts have lived on the space station for six months before, but on those missions, they knew how long they would be in orbit when they left Earth.
Wilmore’s wife, Deanna, told the CBS affiliate in Knoxville, Tennessee, near the family’s hometown, that she is preparing for her husband to be away for Christmas, their 30th wedding anniversary, and their daughters’ school activities. “We probably don’t expect him until February. February or March,” she told WVLT-TV.
“You just sort of have to roll with it and expect the unexpected,” she said.
This story originally appeared on Ars Technica.
