The return to Earth of Boeing’s Starliner capsule will be delayed a few more days due to thruster problems and a planned spacewalk.
NASA announced today (June 18) that Starliner will complete its first human mission to the International Space Station (ISS) no earlier than June 26, nearly three weeks after launch. The landing will take place that day at White Sands Space Harbor in New Mexico at 4:51 a.m. EDT (0851 GMT). We’ll broadcast it live here on Space.com, via NASA Television.
The two-astronaut mission, known as Crew Flight Test (CFT), was originally scheduled to spend about a week at the ISS, but its departure from the ISS has been significantly delayed. NASA and Boeing are using the extra time to continue evaluating problems with the thrusters that hampered Starliner’s first ISS docking attempt on June 6. In addition, a postponed ISS servicing spacewalk will now take place on June 24, two days before Starliner’s scheduled departure.
“We want to give our teams a little more time to look at the data, do some analysis and make sure we’re really ready to come home,” Steve Stich, manager of NASA’s Commercial Crew Program, said during a livestream conference call with reporters today. Starliner can disconnect in an emergency, but tests are otherwise being conducted to learn more about the vehicle’s systems.
Related: Thruster failures and helium leaks can’t stop Boeing’s Starliner astronaut test flight – but why are they happening?
Stich reiterated that five of Starliner’s 28 reaction control thrusters failed during the final phase of the ISS rendezvous on June 6, although four of them eventually came back online. (Starliner succeeded on its second docking attempt, which occurred several hours later, on June 6.) Review of what happened is ongoing. As part of that effort, Boeing and NASA ground team members conducted a thruster hot-fire test with the astronauts this weekend, and afterward, Stich said, everyone feels “very confident.”
One thruster was not fired during the test due to the abnormally low pressure first observed during docking, and will remain offline during return to Earth. (Canadarm2, the space station’s robotic arm, was also used to view the thrusters via a robotic camera, according to ISS program manager Dana Weigel, who also participated in the conference call.)
CFT’s docking was slightly more complex than the only other time Starliner approached the ISS, which was done during an unmanned test flight in May 2022. That unmanned mission, called Orbital Flight Test 2 (OFT-2), also faced problems with the thrust with docking.
But “the deal [for CFT] placed slightly more demands on the propulsion system. In other words, it fired its thrusters a little more often,” Stich said. Additionally, teams are running hardware simulations at NASA’s Marshall Space Flight Center in Alabama to model persistent helium leaks on Starliner.
A small helium leak in one of Starliner’s RCS thrusters was first discovered on the pad in early May, after a launch attempt was aborted due to a valve problem with the capsule’s United Launch Alliance Atlas V rocket.
Several new helium leaks occurred during the mission and a fault tree analysis is currently underway to find out what happened. Stich said the helium leaks and problems with the RCS thruster appear to have different causes, while Mark Nappi, vice president and program manager of Boeing’s commercial crew program, said data research is revealing more and more about what’s happening.
The helium leak on the launch pad was not an immediate safety issue, but upon further investigation, NASA and Boeing discovered a design vulnerability in the RCS system that could affect Starliner’s return. Agency officials subsequently certified a new reentry mode after testing the idea on the ground in simulations with the CFT crew, veteran NASA astronauts Barry Wilmore and Suni Williams, both of whom are former U.S. Navy test pilots.
Wilmore and Williams tested Starliner’s various systems in orbit, and ground teams continued to analyze data to better understand the thruster and helium leak issues.
Stich emphasized that testing in orbit on Saturday (June 15) gave the team confidence that Starliner will recover. “Saturday was a big day of understanding that the helium leaks are gone, and also understanding that the thrusters have been repaired, and that we can count on the thrusters for the rest of the flight,” he said.
While the review of what is happening continues, he said the tone of the conversation has changed. “I think now we’re doing the normal things that we do: what are the contingencies that could happen [with] the time frame for disconnecting? And when we get to this, how we handle each of these contingencies if something were to happen, and then look at the procedures that we have in place. Are we ready to implement this?”
The mission’s delayed return also accommodates a planned June 13 spacewalk, which was postponed due to a problem with “space suit discomfort” during donning. NASA astronaut Matt Dominick, the ISS crew member experiencing discomfort, will not go outside during the rescheduled spacewalk on June 24 to prevent this from happening again, Weigel said during today’s press conference.
Weigel told Space.com that, if the June 24 spacewalk is postponed again, undocking from Starliner would be the priority and NASA astronauts Tracy Caldwell Dyson and Mike Barratt would wait until Starliner took off to perform the extravehicular activity.
CFT is a development mission. During the launch and flight campaign, Boeing and NASA emphasized that mission timelines are therefore in flux as Starliner conducts its first-ever mission with humans on board. Wilmore and Williams said much the same thing, based on their experience flying complex aircraft through the U.S. Navy.
“We’ve always said this is a test flight and we’re going to learn some things. So here we are,” Nappi said during today’s press conference. “We learned that our helium system is not performing, even though it is controllable. It is still working as we designed it. So we need to figure that out.”
Nappi emphasized that the performance of most RCS thrusters is good, nearing nominal, while the helium leaks “show that they are stable and less than measured.” [before]The team is working to learn more about Starliner while the service module, which provides most of the spacecraft’s fuel and power, is still attached to the spacecraft as it will be discarded just before landing.
“This is an opportunity to fully understand the system’s performance, without the pressure of planning or time,” said Nappi. Technical issues aside, the mission met 77 of the original 87 flight test objectives, he noted; the remaining 10 will be evaluated during undocking and landing.
Related: NASA is weighing the potential impact of helium leaks and more on Boeing’s Starliner astronaut test flight
Starliner, together with SpaceX’s Dragon capsule, will be commissioned by NASA to send agency-led crews to the ISS from American soil. (Russia also pilots and launches cosmonaut-led crews on its long-term Soyuz spacecraft.) CFT aims to certify Starliner for the first operational ISS rotational mission, called Starliner-1, expected to launch in 2025.
Dragon and Starliner were first commissioned in 2014 to send NASA astronauts into the skies by 2017, but financial and technical issues extended the timeline by several years. SpaceX, whose Crew Dragon spacecraft is based on the company’s ISS cargo capsule, launched its first astronaut test mission in 2020 after just one uncrewed test flight. Starliner’s first human mission came four years later and required two unmanned tests, in part because the spacecraft was a new design.
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Starliner’s path to CFT was postponed after the capsule encountered problems during its first unmanned test mission in December 2019 and failed to reach the ISS as planned. (Astronauts often say, however, that timelines in development programs like Starliner are difficult to estimate because the unexpected can always occur.)
Boeing addressed these issues, which took time. The outbreak of the coronavirus pandemic in early 2020 further delayed the launch of the second unmanned ISS mission, pushing it back to May 2022. CFT was next expected to launch in 2023, but that flight was postponed after problems with loading parachutes and flammable tape had come to light. last year.
CFT subsequently underwent two scrubs on the pad due to problems with the Atlas V and ground equipment. The first, on May 6, occurred about two hours before launch due to a “buzzing valve” that had to be returned to a company facility for replacement. The second launch attempt on June 1 was scrapped due to a problem with a ground launch sequencer less than four minutes before liftoff.