The two NASA astronauts who traveled to the International Space Station in early June were originally scheduled to return a few weeks ago after completing a test flight of Boeing's Starliner spacecraft.
Instead, astronauts Butch Wilmore and Suni Williams will remain aboard the space station for a few more weeks while NASA and Boeing engineers continue to investigate the malfunction of the spacecraft's thrusters.
But please do not suggest the astronauts are trapped or stranded, officials said Friday, and there is no talk of a rescue mission.
“We are not confined to the ISS,” Mark Nappi, Boeing's Starliner program manager, said at a press conference on Friday. “There is no danger to the crew.”
Steve Stich, manager of NASA's commercial crew program, also tried to ease concerns.
“The space station spacecraft is in good condition,” he said. “I want to be clear that Butch and Suni are not stranded in space. Our plan is to return them aboard Starliner and have them return home at the appropriate time.”
Stich added that the right time would come after further analysis into why five of Starliner's 28 steering jets behaved abnormally as the spacecraft approached the space station, and Starliner's computers, which were guiding the spacecraft autonomously, were able to compensate with the remaining thrusters.
Four of the five thrusters currently appear to be working properly; the remaining thrusters will not be used during the return journey. Mission managers are hopeful that Starliner will be able to detach from the space station and carry Wilmore and Williams back from space, but the cause of the problem is not fully understood.
Deadly disasters in NASA's history, such as the losses of the space shuttles Challenger and Columbia, have taught mission managers to be vigilant and curious when something is wrong.
“I think they're doing their due diligence,” former NASA flight director Wayne Hale said in an interview. “There's no rush to get it back, so it makes a lot of sense to take their time to gather as much information as they can to make sure all of the issues are worked out. It makes a lot of sense to take their time.”
Nappi echoed that assessment in a press conference on Friday, saying it would be prudent to take the time for additional analysis.
“If we have the time and we want to do more, it would be irresponsible for us not to do it,” he said.
Starting next week, engineers will conduct ground tests at NASA's White Sands Test Facility in California using thrusters identical to those on Starliner, which will replicate the thrusters Starliner makes in space.
Stich said that will probably take about two weeks. “After that, we'll give our engineers a chance to look at that thruster,” he said. “This will be a real opportunity to inspect the thruster just like we did in space.”
Engineers can't directly inspect the thrusters that are causing the problem on the spacecraft currently in orbit because they're housed in a part called the Service Module, which will detach during the return flight and burn up in the atmosphere.
“This test will help us understand how the thrusters are performing and maybe give us 100% confidence that everything we see on orbit is OK,” Stich said. “This is just one more piece of data we'll have before we actually deorbit the spacecraft.”
Former NASA officials like Hale say previous fatal accidents were caused by mission managers ignoring engineers' concerns.
During the launch of the Space Shuttle Columbia in January 2003, a piece of insulation broke off from the external tank and struck the shuttle's left wing. Hale, who was about to start his new role as launch integration manager for the shuttle program, called his Pentagon counterparts to ask whether they had the capacity to visually inspect the shuttle for damage.
But NASA's higher-ups in the chain of command weren't interested and told Hale to withdraw his request for help, which he did.
Unknown to everyone at the time, a foam strike had ripped a hole in one of the wings, and Columbia broke apart on its return to Earth, killing all seven astronauts aboard.
“Looking back, we certainly didn't ask enough questions in the Columbia case,” Hale said, “we didn't have enough time. And the lesson was clearly to use the time that was available to get the most complete answers and to answer all the questions that the experts were going to have.”
While NASA and Boeing are working on the spacecraft, Wilmore and Williams could be able to return aboard Starliner if an emergency occurred on the space station, NASA's Stich said. In fact, they temporarily evacuated to Starliner when a Russian satellite suddenly broke apart in orbit on Thursday, and they plan to use Starliner if the space station is hit by large debris.
Due to current design limitations of Starliner's batteries, the capsule is currently certified to stay docked to the space station for 45 days, but Stich said the batteries have performed well so far and the stay could be extended beyond that.
Starliner isn't the only problem NASA has to solve at the moment: A spacewalk was aborted on Monday after water leaked from a cord leading to the astronauts' spacesuits while they were inside the airlock. Engineers still don't understand what happened.
“We need to think about it a bit more,” said Bill Spech, operations integration manager for NASA's International Space Station program.
Spech said the next spacewalk, scheduled for Tuesday, won't take place until at least late July.