Two NASA astronauts who traveled in early June to the International Space Station were originally scheduled to return home a few weeks ago, completing a test flight of Boeing’s Starliner spacecraft.
Instead, astronauts Butch Wilmore and Sonny Williams will remain on the station for several more weeks as NASA and Boeing engineers continue to study the vehicle’s misbehaving thrusters.
But don’t call the astronauts stuck or stranded, officials said Friday. And there is no mention of a rescue mission.
“We’re not stuck on the ISS,” Mark Nappi, Boeing’s Starliner program manager, said during a press conference Friday. “The crew is in no danger.”
Steve Stich, the director of NASA’s commercial crew program, also tried to allay concerns.
“The vehicle at the station is in good condition,” he said. “I want to make it very clear that Butch and Suni are not stranded in space. Our plan is to continue to return them to the Starliner and return them home at the appropriate time.”
Mr. Stich then added that the right time would be after additional analysis of why five of the Starliner’s 28 maneuver jets behaved strangely as the spacecraft approached the space station. The Starliner’s computers, which were autonomously guiding the spacecraft, were able to compensate with the remaining thrusters.
Four of the five thrusters now appear to be working properly. the other thruster will not be used during the trip home. Mission managers expect the Starliner to be able to detach from the space station and pick up Mr. Wilmore and Ms. Williams on their return journey from space, but they do not fully understand what caused the problem.
Deadly disasters in NASA’s history, such as the loss of space shuttles Challenger and Columbia, have taught mission managers to be cautious and curious when things go wrong.
“I think they’re doing their due diligence,” Wayne Hale, a retired NASA flight director, said in an interview. “Since we’re in no rush to get home, it makes a lot of sense to take the time to gather as much information as possible so they can make sure all the issues are resolved. That makes a lot of sense, take your time.”
Mr. Napi offered a similar assessment during Friday’s press conference, saying it was prudent to use the time for additional analysis.
“It would be irresponsible of us, if we have the time and want to do more, not to,” he said.
Starting next week, engineers will conduct ground tests at NASA’s White Sands Test Facility in California using a thruster identical to those on the Starliner. The shots will replicate those fired by the Starliner in space.
That will likely take a few weeks, Mr. Stich said. “Then we’ll give the engineers a chance to go look at that thruster,” he said. “This will be the real opportunity to look at a booster, just like we’ve had in space.”
Engineers won’t be able to directly examine the pesky thrusters on the spacecraft now in orbit because they’re in what’s known as a service module. This part will be discarded during the flight home and will burn up in the atmosphere.
“The test will help us understand the performance of the booster and can give us 100 percent confidence that everything we’ve seen in orbit is OK,” Mr Stich said. “It’s just one more piece of data that we can have before we actually deploy the vehicle.”
Former NASA officials such as Mr. Hale noted that mission managers brushing aside engineers’ concerns contributed to previous fatal accidents.
During the launch of space shuttle Columbia in January 2003, a piece of insulating foam from the external fuel tank broke off and struck the shuttle’s left wing. Mr. Hale, who was about to start a new position as director of launch integration for the shuttle program, called the Defense Department, asking if he could visually inspect the shuttle for damage.
But managers higher up NASA’s chain of command were not surprised and told Mr. Hale to withdraw the request for help. He complied.
What no one knew at the time was that the foam blow had blown a hole in the wing. As it returned to Earth, Columbia disintegrated, killing all seven astronauts on board.
“Looking back, certainly in the case of Columbia, not enough questions were asked,” Mr. Hale said. “There wasn’t enough time. And the lesson was clearly learned that you take the time available to get to the most complete answer and answer all the questions that any of the experts might have.”
While NASA and Boeing are studying the spacecraft, NASA’s Mr. Stich said, Mr. Wilmore and Ms. Williams will be able to board the Starliner to head home in the event of an emergency on the space station. Indeed, when a dead Russian satellite unexpectedly disintegrated in orbit on Thursday, they briefly took refuge in the vehicle and would have used it if the space station had been hit by a large piece of debris.
The capsule is currently certified to spend 45 days docked to the space station due to limitations in the Starliner’s current battery design. But so far, the batteries are performing well and the stay can be extended beyond 45 days, Mr. Stich said.
Starliner isn’t the only problem NASA has to solve right now. A spacewalk was interrupted Monday when water leaked from an umbilical cord attached to a space suit while the astronauts were in the vent. The engineers still don’t understand what happened.
“We have to go and think about it a little bit more,” said Bill Spetch, NASA’s director of operations integration for the International Space Station program.
The next spacewalk, which had been scheduled for Tuesday, will not take place until at least late July, Mr. Spetz said.
