Two NASA astronauts who traveled to the International Space Station in early June were originally scheduled to return home a few weeks ago, having completed a test flight of the Boeing Starliner spacecraft.
Instead, the astronauts, Butch Wilmore and Suni Williams, will remain on the station for several weeks longer as NASA and Boeing engineers continue to study the vehicle’s misbehaving thruster.
But don’t call the astronauts stranded 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 news conference Friday. “The crew is in no danger.
Steve Stich, manager of NASA’s commercial crew program, tried to allay fears.
“The vehicle at the station is in good condition,” he said. “I want to make it very clear that Butch and Suni are not stuck in space. Our plan is to continue returning them on the Starliner and bring them home at the right time.”
Mr. Stich then added that the right time would be after additional analysis of why five of the Starliner’s 28 maneuvering thrusters were behaving strangely as the spacecraft approached the space station. The Starliner’s computers, which guided the spacecraft autonomously, were able to compensate with the remaining thrusters.
Four of the five jets now appear to be working properly; the other nozzle will not be used during the trip home. Mission managers expect the Starliner to be able to detach from the space station and take Mr. Wilmore and Ms. Williams on the return trip from space, but they don’t 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 something isn’t quite right.
“I think they’re doing their due diligence,” Wayne Hale, NASA’s former flight director, said in an interview. “In order not to rush 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. It makes a lot of sense to take your time.’
Mr. Nappi offered a similar assessment during Friday’s news conference, saying it was prudent to use the time for further analysis.
“It would be irresponsible for us, if we have the time and want to do more, not to do it,” he said.
Early next week, engineers will conduct ground tests at NASA’s White Sands Test Facility in New Mexico using a nozzle identical to those on the Starliner. The shots will reproduce those performed by the Starliner in space.
That will likely take several weeks, Mr. Stich said. “Then we’ll give the engineers a chance to look at that nozzle,” he said. “It’s going to be a real opportunity to explore the jet, just like we’ve had in space.”
Engineers won’t be able to directly examine the problematic thrusters on the spacecraft, which is now in orbit, because they are located on the so-called 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 thrusters and can give us 100% confidence that everything we saw in orbit is OK,” Mr Stich said. “It’s just another piece of data that we can have before we actually get the vehicle out of orbit.”
Former NASA officials such as Mr. Hale noted that mission managers dismissed engineers’ concerns and contributed to earlier fatalities.
During the launch of Space Shuttle Columbia in January 2003, a piece of insulating foam broke loose from the external fuel tank and struck the space shuttle’s left wing. Mr. Hale, who was about to start a new position as manager of launch integration for the space shuttle program, called his Defense Department contacts and asked if he could visually inspect the shuttle for damage.
But managers higher up NASA’s chain of command were not amused and told Mr. Hale to withdraw the request for help. He complied.
No one knew at the time that the foam blow had blown a hole in the wing. When Columbia returned to Earth, it disintegrated, killing the seven astronauts on board.
“In retrospect, certainly not enough questions were asked in the Columbia case,” Mr. Hale said. “It wasn’t enough time. And we clearly learned that you take the time that is available to get the most complete answer and answer any questions that any of the experts might have.”
While NASA and Boeing study the spacecraft, NASA’s Mr. Stich said Mr. Wilmore and Ms. Williams would be able to hop into the Starliner and head home in case of an emergency to the space station. When a dead Russian satellite unexpectedly disintegrated in orbit on Thursday, they briefly took refuge in the vehicle, which they would use if a large piece of debris hit the space station.
The capsule is currently certified to spend 45 days docked at the space station, due to the limitations of the Starliner’s current battery design. But so far the batteries have performed well and the stay can be extended beyond 45 days, Mr. Stich said.
Starliner isn’t the only problem NASA needs to solve right now. The spacewalk was interrupted on Monday when water leaked from the umbilical cord that connects to the spacesuit while the astronauts were in the airlock. The engineers still don’t understand what happened.
“We still have to think about it,” said Bill Spetch, NASA’s operations integration manager for the International Space Station program.
The next spacewalk, which was scheduled for Tuesday, won’t happen until at least the end of July, Mr. Spetch said.