The return to Earth of Boeing’s Starliner capsule is on indefinite hold pending results of new thruster tests and ongoing analysis of helium leaks that cropped up during the ship’s rendezvous with the International Space Station, NASA announced Friday.

But agency officials insisted Starliner commander Barry “Butch” Wilmore and co-pilot Sunita Williams are not “stranded” in space.

“We don’t have a targeted (landing) date today,” Steve Stich, NASA’s Commercial Crew Program manager, told reporters during a teleconference. “We’re not going to target a specific date until we get that testing completed.

“So essentially, it’s complete the testing, complete the fault tree, bring that analysis into (the mission management team) and then have an agency-level review. And then we’ll lay out the rest of the plan from undock to landing. I think we’re on a good path.”

The problem for NASA and Boeing is that the Starliner’s service module, which houses the helium lines, thrusters and other critical systems, is discarded before re-entry and burns up in the atmosphere. Engineers will not be able to study the hardware after the fact and as a result, they want to collect as much data as possible before Wilmore and Williams head home.

But the crew’s repeatedly extended stay at the space station has prompted some observers to say Wilmore and Williams are stranded in orbit, an impression that seems to have taken root in the absence of updates from NASA as the target landing date was repeatedly pushed back.

Stich and Mark Nappi, Boeing’s Starliner program manager, said that description is a mis-characterization.

“It’s pretty painful to read the things that are out there” Nappi said. “We’ve gotten a really good test flight … and it’s being viewed rather negatively. We’re not stuck on ISS. The crew is not in any danger, and there’s no increased risk when we decide to bring Suni and Butch back to Earth.”

Said Stich: “I want to make it very clear that Butch and Suni are not stranded in space. Our plan is to continue to return them on Starliner and return them home at the right time.

“We’ll have a little bit more work to do to get there for the final return, but they’re safe on space station. Their spacecraft is working well, and they’re enjoying their time on the space station.”

The Starliner was launched June 5 on the program’s first piloted test flight with one already known helium leak. The other four developed during the ship’s rendezvous with the space station when the jets were rapidly pulsed to fine tune the Starliner’s approach.

While docked at the station, valves are closed to isolate the helium system, eliminating any additional leakage. But once Wilmore and Williams depart and head for home, the valves will be re-opened to repressurize the lines, or manifolds.

Stich said even with the known leaks, the spacecraft will have 10 times the amount of helium it needs to get home. But engineers want to make sure the leaks won’t get worse once the system is again pressurized.

The five aft-facing thrusters in the Starliner’s service module also failed to operate properly during approach to the space station on June 6.

After docking, four of the five jets were successfully test fired and despite slightly lower power levels than expected, they are considered good to go for undocking and re-entry. The fifth thruster was not “hot fired” because it’s earlier performance indicated it had actually failed.

But managers want to find out what caused the unexpected behavior in the other four. Starting next week, a new thruster identical to the ones aboard the Starliner will be test fired at a government facility at White Sands, N.M., exactly like the those in orbit were fired during the Starliner’s rendezvous and docking.

“We’ll recreate that profile,” Stich said. “Then we’ll put a pretty aggressive profile in the thruster for (the undocking-to-re-entry) phase.

It’s possible the glitches with the aft-facing thrusters were caused by higher-than-normal temperatures due to the Starliner’s orientation with respect to the sun, or the sequence of rapid, repetitive firings commanded by the flight software. Or both.

The ground tests, expected to last “a couple of weeks,” may provide evidence one way or the other.

“This will be a real opportunity to examine a thruster just like we’ve had in space on the ground, a detailed inspection,” Stich said. “Once that testing is done, then we’ll look at the plan for landing.”

As for the impression the crew is stranded in space, Stich and Nappi both pointed out that on Wednesday, a defunct Russian satellite in a slightly lower, more tilted orbit than the space station suffered a catastrophic “event” that produced more than 100 pieces of trackable debris.

While flight controllers evaluated the trajectories of the wreckage, the space station’s nine-member crew was told to “shelter in place” aboard their respective spacecraft, ready to immediately depart and return to Earth in case of a damaging impact.

Two Russian cosmonauts and NASA’s Tracy Dyson boarded their Soyuz ferry ship while three NASA astronauts and another cosmonaut floated into their SpaceX Crew Dragon. Wilmore and Williams rode out safe haven inside the Starliner and were cleared to fly home if warranted.

After about one hour, the crew was given the all clear to return to normal work. Had the Starliner had been considered unsafe, Wilmore and Williams likely would have been told to seek refuge in the Crew Dragon. But that was not the case.

“We have an approval to be a lifeboat in case of an emergency on ISS,” Nappi said. “That means we can return with the Starliner at any time, and that was proven this week.”

NASA and Boeing managers have again decided to extend the Starliner crew capsule’s stay at the International Space Station, passing up a June 26 re-entry to allow more time for analysis and testing to make sure helium leaks and thruster failures are fully understood, officials said late Friday.

NASA plans to hold a formal re-entry readiness review before setting a new landing target date. Given the on-going analysis, the Starliner’s undocking and return to Earth likely will slip past two already planned space station spacewalks on Monday and July 2.

In the meantime, Starliner commander Barry “Butch” Wilmore and co-pilot Sunita Williams are still cleared to undock and fly home at any time if a station malfunction or other issue crops up that requires a quick departure. As such, officials say they are not stranded in space.

“We are taking our time and following our standard mission management team process,” Steve Stich, manager of NASA’s Commercial Crew Program, said in a statement. “We are letting the data drive our decision making relative to managing the small helium system leaks and thruster performance we observed during rendezvous and docking.”

In addition, he said, given the extended duration of the Starliner mission “it is appropriate for us to complete an agency-level review, similar to what was done ahead of the NASA’s SpaceX Demo-2 return after two months on orbit, to document the agency’s formal acceptance on proceeding as planned.”

He was referring to the first flight of astronauts aboard SpaceX’s Crew Dragon ferry ship in 2020. But the Demo-2 mission did not experience problems like the ones noted so far in the Starliner’s first piloted test flight.

The issue for Starliner troubleshooters is that the helium leakage and the thrusters in question are located in the Starliner’s drum-shaped service module, which is attached to the base of the crew capsule. The service module is jettisoned prior to re-entry and burns up in the atmosphere.

Given that engineers will not be able to examine the actual hardware after the fact, NASA and Boeing managers want to give them as much time as possible to review telemetry, to continue testing and to polish contingency scenarios in case additional problems show up after undocking.

They also want to learn as much as possible about what might be needed to prevent similar problems in downstream flights. NASA managers were hoping to certify the Starliner for operational crew rotation flights to the ISS starting early next year, but it’s not yet clear if that’s remains a realistic goal.

In any case, Stich said the Starliner “is performing well in orbit while docked to the space station.”

“We are strategically using the extra time to clear a path for some critical station activities while completing readiness for Butch and Suni’s return on Starliner and gaining valuable insight into the system upgrades we will want to make for post-certification missions.”

Already running four years behind schedule, the Starliner was launched June 5, a month later than planned due to minor problems with its Atlas 5 rocket, trouble with a countdown computer and because of an initial helium leak in the system used to pressurize the capsule’s thrusters.

NASA and Boeing managers decided the leak was too small to pose a safety threat and the ship was cleared for launch. Once in orbit and on the way to the space station, however, four more helium leaks developed and the Starliner’s flight computer took seven maneuvering jets off line when the telemetry did not match pre-launch expectations.

One thruster was deemed unusable going forward, but the others were successfully test fired last Saturday. That “hot-fire” test gave engineers confidence the jets needed for post-undocking maneuvers and the critical de-orbit “burn” will work as needed to drop the ship out of orbit for re-entry.

Likewise, officials said they were confident the helium leaks could be managed even if one or more gets worse after undocking. Only seven hours of helium is needed for the return to Earth and the Starliner has more than 10 times that amount left on board.

Working around multiple helium leaks and thruster problems, the crew of Boeing’s Starliner spacecraft wrapped up a challenging rendezvous and a delayed-but-successful docking with the International Space Station Thursday in a major milestone for the new ship’s first piloted test flight.

With commander Barry “Butch” Wilmore and co-pilot Sunita Williams monitoring the Starliner’s automated approach, the Starliner’s docking mechanism engaged its counterpart on the front of the station’s forward Harmony module at 1:34 p.m. EDT as the two spacecraft were sailing 260 miles above the Indian Ocean.

A few moments later, the Boeing ferry ship was pulled in for a “hard” mating, ensuring an airtight structural seal.

“That was an OK, three-wire, fly Navy docking complete!” mission control radioed.

“OK indeed,” replied Wilmore, a veteran astronaut and former Navy test pilot. “Nice to be attached to the big city in the sky.”

After extensive checks to verify an airtight seal, hatches were opened and Wilmore and Williams floated into the lab complex to an enthusiastic welcome from the seven Expedition 71 crew members: cosmonauts Oleg Kononenko, Nicolai Chub and Alexander Grebenkin, along with NASA astronauts Matthew Dominick, Michael Barratt, Jeanette Epps and Tracy Dyson.

“I’m not sure we could have gotten a better welcome,” Wilmore said, smiling broadly. “We had music, we had dancing, it was great! What a wonderful place to be.”

Said Williams: “I just want to say a big thanks to family and friends who’ve lived this for a long time,” she said amid laughter. And I think you’re glad we’re not with you anymore! … We’re just happy as can be to be up in space.”

Wilmore and Williams plan to spend about a week aboard the outpost before returning to Earth aboard the Starliner. While they’re there, the station crew will install a replacement urine processor pump module that was loaded aboard the Starliner at the last minute to fix the lab’s water recycling system and allow normal use of the toilet in the U.S. segment of the station.

Running years behind schedule after multiple problems that cost Boeing some $1.4 billion to correct, the Starliner was launched Wednesday with a known helium leak in the system used to pressurize the spacecraft’s propulsion system. Launch had been delayed a month, in part because of work to confirm the ship could safely be launched with the leak as is.

After reaching orbit, two more helium leaks developed that prompted flight controllers to close valves leading to the affected plumbing, or manifolds, while they analyzed leak rates and potential work arounds. Closing the manifolds took down five of 28 reaction control system jets in the ship’s service module and three of 20 more powerful “OMAC” thrusters.

“Wow. Yesterday was exciting, and I didn’t think we could make it more exciting, and we did that today,” said Mark Nappi, Boeing’s Starliner program manager. “It was amazing. We accomplished a lot and really more than expected. We exercised the team, we exercised the crew and just had an outstanding day.”

He was referring to the crew, flight controllers and engineers who faced a fresh set of problems Thursday, working in concert through the night and day to develop the procedures necessary to ensure a safe, successful docking.

Kicking off the final stages of the rendezvous, the two leaking manifolds discovered Wednesday were re-opened to provide the helium pressure needed to operate all the spacecraft’s available thrusters as needed.

Engineers then had to deal with five RCS jets that were “deselected” by the capsule’s flight software when telemetry showed they were not performing exactly as expected. Nappi said the thrusters all appeared to be firing normally, but likely were deemed unusable because performance did not exactly match specifications written into the software. Similar issues were seen in the same aft-facing thrusters during an earlier unpiloted Starliner test flight when the jets were commanded to repeatedly fire in quick succession.

It’s not yet known why the performance didn’t match the software’s expectations, but flight controllers managed to re-enable four of the five RCS jets after test firing them one by one. But by that point, the crew was forced to shift to a backup docking opportunity.

Throughout the process, Wilmore flew the Starliner manually, holding position about 650 feet from the space station. When ground teams concluded the spacecraft had enough thruster redundancy to proceed, the Starliner’s automated control system took over and flew the ship in for a problem-free docking.

As if the team hadn’t had enough problems to deal with, a fourth helium leak was detected after docking. In any case, per standard procedure, flight controllers closed all the Starliner’s helium manifolds after the linkup to prevent any residual leakage while attached to the station.

Despite the leaks, NASA officials said more than enough helium remains on board to ensure a safe return to Earth at the end of a normal-duration or even extended mission.

The helium leaks are all located in the Starliner’s drum-shaped service module, which is discarded to burn up in the atmosphere before the crew capsule re-enters for landing.

Given post-flight inspections are not possible, Boeing engineers are already planning inspections of hardware being built for downstream flights to look for signs of trouble and to develop possible screening procedures to identify problems well before flight.

Asked to characterize the problems encountered by the Starliner to date, Nappi said they were relatively minor and similar to issues faced by other spacecraft, including the shuttle, making their initial flights.

“We have two problems on this vehicle right now: the helium leak and figuring out how to fine tune these thrusters so that they’re not selected off,” he said. “Those are pretty small, really, issues to go deal with, and we’ll figure them out for the next mission. So I don’t see these as significant at all.”

Russian cosmonaut Oleg Kononenko continues to cement a place in the annals of space history with his historic mission on board the International Space Station. On Wednesday, he became the first person to reach 1,000 cumulative days in space.

The milestone comes amid his fifth flight to space and during his third stint as the commander of the ISS. Back in February, Kononenko broke the cumulative in-space record of 878 days, which was previously held by former cosmonaut Gennady Padalka.

His most recent trip to the orbiting laboratory began with a launch aboard the Soyuz MS-24 spacecraft on Sept. 15, 2023, alongside cosmonaut Nikolai Chub and NASA astronaut Loral O’Hara. He’s scheduled to return with Chub and NASA astronaut Tracy Dyson in September 2024.

Spaceflight Now spoke with Emmanuel Urquieta, the former chief medical officer of the NASA-funded Translational Research Institute for Space Health (TRISH), which is led by Baylor College of Medicine. He was recently tapped by the University of Central Florida (UCF) to serve as the vice chair for aerospace medicine in its Department of Internal Medicine.

“It takes a special kind of person to be able to achieve such a record,” Urquieta said. “It’s a long time, but I think that it is one of those data points that I hope that we will start getting more of those in the future.”

Urquieta participated in research concerning a number of astronauts who have traveled to low Earth orbit for varying lengths of time, including the first all-civilian mission, called Inspiration4, in 2021. He pointed to five main areas of research that he and his colleagues hone in on when it comes to better understanding long duration spaceflight:

• Communication across a large distance from Earth
• Radiation exposure
• Isolation and confinement
• Altered gravity fields (i.e. being in a zero g environment)
• Living in a hostile and closed environment

He said Kononenko provides a unique opportunity to further our understanding of the impacts of long-duration spaceflight on the human body.

“Even though people might ask, ‘Ok, well, it’s not a single mission, right? There were multiple missions that made that 1,000 days? Well, still in that case, it is extremely relevant to us to understand how multiple exposures to spaceflight have had impacts, in what extent, in the different physiological levels,” Urquieta said.

“I’m sure that there will be a lot of research coming up in the future when he comes back to Earth and I’m sure that there will be a very long follow up with him, you know, days, months and years after, to try really to understand these very unique data points.”

With an eye on long-duration missions on the surface of the Moon in the 2030s and expeditions to Mars further down the road, Urquieta said it’s important to learn as much as possible about things like radiation exposure, eye health, bone loss and space motion sickness.

He said much of that learning comes from the six-month crew rotation missions onboard the ISS.

“When you extrapolate the data that we have from six-month missions to 900 days, there’s still a huge gap of data that we need to fulfill, that we need to get so that we can safely say that, ok, we have enough data that we can confidently say that we’re able to send someone to Mars and make sure that that person is going to come back as healthy as he or she left Earth,” Urquieta said.

Unrivaled record

After Kononenko, the next most experienced flier, who is also currently eligible for future missions, is former NASA astronaut Peggy Whitson. She currently works as a private astronaut at Houston-based Axiom Space and notched more than 675 days on orbit, including her first mission as a private commander of Ax-2 in 2023.

The active duty NASA astronaut who comes closest to Kononenko’s record is Mark Vande Hei who spent a total of more than 523 days in orbit during two separate missions.

Currently, NASA isn’t planning missions to the ISS longer than about six months. The agency uses the SpaceX Crew Dragon to ferry its astronauts to space for these long-duration missions before they hand over on-orbit duties to the following crew. The agency plans to use Boeing’s Starliner spacecraft to do the same, once it is certified in the aftermath of the Crew Flight Test.

The most recent instance of a NASA astronaut spending a continuous year in space was Frank Rubio’s first trip to orbit. His 370 days on orbit were unplanned due to an issue with the Soyuz vehicle that was deemed unsafe to return him and his Russian colleagues to Earth.

Urquieta said he would like to see more year-long missions planned as time goes on and NASA gets closer to sending humans to Mars. But he said the six-month missions are still valuable as the Artemis program prepares to send humans back to the Moon for increasingly longer stays.

“Those late Artemis missions are going to be longer in duration and those ones are going to be a testbed for Mars. So, I expect that those late Artemis missions will be increasing in duration, maybe to the extent of longer than a year,” Urquieta said. “But for the Moon, I think that six-month missions on the ISS still provides valuable and reliable information to keep informing the decisions for Moon landing or lunar exploration-type of missions.”

And even if Kononenko’s towering record stands for years to come, Urquieta said the more we learn about the human body in space, the better we can treat older humans here on Earth and different types of diseases. Not only that, but he said working more with medicine in space can offer better solutions when it comes to healthcare for those in homes and communities that are far removed from hospitals or clinics.

“Even still here in the U.S., there are lots of populations that are 100 miles away from the closest hospital and from the closest pharmacy,” Urquieta said. “Imagine that capability of not having to see a physician and you will still be able to have some initial medical decision support and initiate the treatment.”

“I think that will be extremely, extremely relevant to underserved and isolated populations, not only in the U.S., but really in the world.”

After nearly three weeks of exhaustive tests and data analysis, NASA managers said Friday they are confident Boeing’s oft-delayed Starliner crew capsule can safely launch “as is” June 1, saying a small helium leak in the ship’s propulsion system does not pose a flight safety concern.

Steve Stich, manager of NASA’s Commercial Crew Program, said even if a suspect shirt-button-size rubber seal in the plumbing leading to one specific thruster failed completely in flight — resulting in a leak rate 100 times worse than what’s been observed to date — the Starliner could still fly safely.

“Should we be wrong about something, we could handle up to four more leaks,” he said. “And we could handle this particular leak if that leak rate were to grow, even up to 100 times in this one (propulsion module).”

What will now be a nearly one-month-long launch delay was required because “we needed to take the time to work through this analysis, and to understand the helium leak and understand the ramifications of that,” Stich said.

And to give the work force time off over the Memorial Day holiday weekend.

The Starliner’s two NASA crew members, commander Barry “Butch” Wilmore and co-pilot Sunita Williams, plan to fly back to the Kennedy Space Center next Tuesday to prepare for launch from the Cape Canaveral Space Force Station atop an Atlas 5 rocket at 12:25 p.m. EDT June 1.

If all goes well, they will dock at the International Space Station the next day and return to Earth on June 10.

Wilmore and Williams were in the process of strapping in for launch May 6 when the countdown was aborted because of problems with an oxygen pressure relief valve in their Atlas 5’s Centaur upper stage. Rocket-builder United Launch Alliance hauled the booster back to a processing facility and replaced the valve without incident.

At the same time, Boeing engineers began a detailed investigation of a small helium leak in one of the Starliner’s four propulsion modules, known as “doghouses,” that showed up when valves were closed as part of normal post-scrub procedures.

The leak eventually was traced to a flange where propellant lines feeding a specific reaction control system thruster in the port doghouse come together. The Starliner is equipped with 28 RCS jets, and helium is used to pressurize the propellant lines, opening and closing valves in each doghouse as needed.

Because traces of extremely toxic propellants could still be present in the plumbing, the seal could not be replaced or even inspected while the capsule was still attached to the Atlas 5. The Starliner would first have to be hauled back to Boeing’s processing hangar at the Kennedy Space Center for invasive repairs that would trigger a lengthy delay.

Instead, NASA and Boeing ordered tests and analysis to fully understand the leak and what sort of problems it might cause in flight. The observed leak rate did not appear to be a concern, but engineers needed to gain confidence it would not dramatically worsen. They also wanted to make sure no other systems were affected.

Stich said the seal in question likely was crimped or had a tiny defect, allowing helium to slip through. But testing showed that even if the seal was removed from the flange, the Starliner could still fly safely. The helium manifold in question could be isolated and the Starliner’s many other thrusters could easily compensate.

Mark Nappi, Boeing’s Starliner program manager, said the May 6 launch scrub had a “silver lining,” because it brought the helium leak to everyone’s attention and “we now know exactly where it was, we have done all the work to understand the root cause and that’s going to help us with improving the system in the future.”

“Had we launched … it would have been a safe flight and a successful flight,” he said, “but we would have not known as much as we know today.”

That includes one unexpected result, what Stich called “a design vulnerability.” The investigation shows that in the very remote chance of major trouble with two adjacent doghouses, including the one with the helium leak, the Starliner could lose redundancy for the thruster firing needed to drop out of orbit for re-entry.

The Starliner was designed to support three redundant de-orbit capabilities. In one, the braking burn is carried out with four powerful orbital maneuvering and attitude control — OMAC — thrusters. The burn also can be carried out with just two working OMAC jets, or with eight smaller RCS thrusters by firing them longer than planned.

In the right circumstances, with adjacent doghouse modules out of action, the Starliner could lose the full eight-thruster RCS deorbit capability.

“We’ve worked with the vendor of the thruster, Boeing and our NASA team to come up with a redundant method to do the orbit burn, to break it up into two burns about 10 minutes each, 80 minutes apart, to come up with a four-RCS-thruster deorbit burn and to regain the capability of the original system,” Stich said.

Plans to launch Boeing’s oft-delayed Starliner spacecraft on its first crewed test flight Saturday were put on hold Tuesday night to give managers more time to evaluate a small helium leak in the ship’s propulsion system. A new launch target was not announced.

The Starliner’s crew — commander Barry “Butch” Wilmore and co-pilot Sunita Williams — remained at the Johnson Space Center in Houston awaiting word on when to head for the Kennedy Space Center to make final preparations for launch to the International Space Station.

They had hoped to blast off at 3:09 p.m. EDT Saturday, assuming NASA and Boeing managers agreed it would be safe to launch the spacecraft “as is,” with a small-but-persistent leak in the ship’s propulsion pressurization system.

But multiple sources said earlier Tuesday that option was no longer on the table as additional meetings were planned to discuss the rationale for launching the spacecraft assuming the leak would not worsen in flight.

In a short statement late Tuesday, NASA said “the team has been in meetings for two consecutive days, assessing flight rationale, system performance and redundancy. There is still forward work in these areas, and the next possible launch opportunity is still being discussed.”

NASA did not announce when the analysis might be complete or when another launch attempt might be made. Near-term launch opportunities beyond Saturday and Sunday, based on the Starliner’s ability to match the station’s orbit, are May 28, June 1 and 2 and June 5 and 6.

The latest delay was a familiar setback for the hard-luck Starliner, which has suffered a steady stream of frustrating setbacks since an initial unpiloted test flight in 2019 was derailed by software problems and communications glitches. A second uncrewed test flight was launched and while it was generally successful, more problems were discovered after its return to Earth.

The helium leak was first detected during a launch attempt on May 6. At the time, engineers concluded the leak rate was small enough to permit launch, but the countdown was called off after engineers with Atlas-builder United Launch Alliance noted unusual behavior in an oxygen pressure relief valve in the rocket’s Centaur upper stage.

Managers eventually decided to haul the rocket back to the company’s Vertical Integration Facility to replace the valve. That work was completed without incident and the new valve was cleared for flight.

Boeing engineers took advantage of delay to carry out a more thorough assessment of the helium leak, which was traced to a specific reaction control system thruster in one of four “doghouse” assemblies mounted around the exterior of the Starliner’s drum-shaped service module.

Each doghouse features four orbital maneuvering and attitude control — OMAC — thrusters and four smaller reaction control system maneuvering jets. Pressurized helium gas is used to push propellants to the rocket motors in each doghouse as well as to four powerful launch abort engines that would only be fired in the event of a catastrophic booster failure.

Engineers tightened bolts around the flange where the leak was detected, pressurized the lines and then ran tests to determine if the leak was still present. In the meantime, launch was re-targeted for May 21 and then, when tests revealed the leak was still present, to Saturday to give engineers more time to assess the data.

The flight is now on hold indefinitely, pending results of the ongoing analysis.

Launch of a United Launch Alliance Atlas 5 rocket carrying Boeing’s Starliner capsule is slipping another four days, from Friday to next Tuesday, to give engineers time to make sure a helium leak in the crew ship’s propulsion system has been resolved, officials said Tuesday.

Liftoff from pad 41 at the Cape Canaveral Space Force Station is now targeted for May 21 at 4:43 p.m. EDT, setting up a docking at the International Space Station the following afternoon. The flight is expected to conclude with a landing at White Sands, New Mexico, around May 30.

Mission commander Barry “Butch” Wilmore and co-pilot Sunita Williams had hoped to take off on the Starliner’s first piloted flight last Monday. They were in the process of strapping in when the countdown was called off because of trouble with an oxygen pressure relief valve in the rocket’s Centaur upper stage.

Two days later, the Atlas 5 was hauled off the launch pad and moved back to ULA’s nearby Vertical Integration Facility where the suspect valve was replaced. Tests confirmed the rocket is good to go for another launch try.

The unrelated helium leak in the Starliner’s propellant pressurization system was noted during the countdown last week, but it remained within safe limits for flight. After the Atlas 5 and Starliner were rolled back to the VIF for the oxygen valve replacement, managers decided to take a closer look at the helium issue.

The leak was detected in plumbing making up a helium manifold inside one of four “doghouse” assemblies spaced around the exterior of the Starliner’s drum-shaped service module. Each doghouse features four orbital maneuvering and attitude control — OMAC — thrusters and four small reaction control system maneuvering jets.

Pressurized helium gas is used to push propellants to the rocket motors in each doghouse, as well as four powerful motors at the base of the spacecraft that would be used during an in-flight abort to propel the capsule away from a malfunctioning booster. The leak was traced to a flange on a single RCS thruster.

Bolts were retorqued and engineers believe the system is flight ready. But managers decided to pressurize the helium lines throughout the spacecraft so engineers can monitor them over time to make sure the lines are, in fact, leak free or within acceptable limits.

“As a part of the testing, Boeing will bring the propulsion system up to flight pressurization just as it does prior to launch, and then allow the helium system to vent naturally to validate existing data and strengthen flight rationale,” the company said in a statement.

“Mission teams also completed a thorough review of the data from the May 6 launch attempt and are not tracking any other issues.”

Wilmore and Williams, both veteran Navy test pilots and astronauts with four flights to the station between them, flew back to the Johnson Space Center in Houston last Friday for additional simulator training. They are expected to fly back to Florida late this week to gear up for another launch try.

The Starliner is one of two commercially procured crew ferry ships ordered by NASA in the wake of the shuttle program’s retirement in 2011. SpaceX won a contract valued at $2.6 billion for development of the company’s Crew Dragon spacecraft and Boeing was awarded $4.2 billion to develop the Starliner.

The goal was to spur development of independent, commercially-operated spacecraft capable of carrying astronauts to and from the International Space Station. Ordering spacecraft from different vendors would allow NASA to continue sending crews to the space station even if a problem grounded one company’s ferry ship.

SpaceX launched its first two-man crew in 2020. Since then, the company has launched eight NASA-sponsored crew rotation flights to the station, three commercial research missions to the lab and a privately-funded, two-man, two-woman trip to low-Earth orbit. In all, 50 people have flown to space aboard Crew Dragons.

Wilmore and Williams will be the first astronauts to fly aboard a Starliner after a series of technical glitches that included major software problems during an initial unpiloted test flight in December 2019 and corroded propulsion system valves that delayed a second uncrewed test mission to May 2022.

The second test flight, paid for by Boeing, was a success, but engineers ran into additional questions about parachute harness connectors and protective tape wrapped around wiring that posed a fire risk in a short circuit. Work to correct those issues and others delayed the first piloted launch to this month.

The Atlas 5 oxygen valve problem was United Launch Alliance’s responsibility. The helium leak responsible for the latest delay goes on the Starliner list, but it was considered a relatively minor problem. That said, managers are leaving no stone unturned to ensure flight safety.

Years behind schedule and more than a billion dollars over budget, Boeing’s Starliner capsule is finally poised for its first piloted launch Monday, a critical test flight carrying two veteran astronauts to the International Space Station and in so doing, demonstrate an alternative to SpaceX’s already operational Crew Dragon.

While SpaceX has launched 50 astronauts, cosmonauts and civilians to orbit in 13 piloted Crew Dragon flights since May 2020, Boeing has been bedeviled by multiple technical problems that required extensive re-work — and an additional unpiloted test flight — to resolve.

But mission managers say all the known issues have been corrected, multiple other upgrades and improvements have been implemented and the spacecraft has been thoroughly tested to verify it is finally ready to safely carry astronauts to and from the space station.

No one is more eager for launch than the Starliner’s crew, both active-duty NASA astronauts.

“I have full confidence in the management that makes the decisions that filter down to the operations team, full confidence on the NASA side and the Boeing side,” said mission commander Barry “Butch” Wilmore. “There have been some issues in the past. That’s the past. That is not now.”

Co-pilot Sunita Williams agreed, adding “I feel like we’ve had a lot of lessons learned, and they’ve been incorporated. … We wouldn’t say we’re ready if we weren’t ready.”

The Starliner’s long-awaited liftoff atop a United Launch Alliance Atlas 5 rocket at the Cape Canaveral Space Force Station is targeted for 10:34 p.m. EDT Monday, roughly the moment Earth’s rotation carries launch complex 41 into alignment with the space station’s orbit.

Wilmore and Williams are well suited to take the Starliner for its first piloted test drive. Both are former Navy test pilots and two of NASA’s most seasoned astronauts with four space flights, 11 spacewalks and 500 days in orbit between them. Both have flown to space aboard the space shuttle and Russia’s Soyuz crew ferry ship.

Now they are flying a new spacecraft on its first piloted flight.

“I remember getting selected for Test Pilot School and (wondering) if I’ll ever be the first to do something in an airplane that’s never been done,” Wilmore, a former F/A-18 carrier pilot, Desert Storm veteran and pastor, told CBS News. “Never in my wildest dreams would I have imagined to be the crew for the first flight of a spacecraft. And here we are.”

Along with chalking up the first piloted flight of the Starliner, it will be the first launch of astronauts using an Atlas rocket since Gordon Cooper’s final Mercury flight more than 60 years ago.

While hundreds of Atlas’s have been launched since then, the latest-generation Atlas 5, equipped with a Russian-built RD-180 first stage engine, is once again “human rated,” with high-reliability components and a state-of-the-art emergency fault detection system designed to trigger a safe escape in the event of an impending launch failure.

“We’ve both been to a couple of launches,” Williams said. “One of them was an Air Force payload. I found out the price tag on that payload, and I was like, okay, if they’re launching that on that Atlas 5, I feel very comfortable sitting on (an) Atlas 5! It’s a great rocket.”

If the Atlas 5 runs into unexpected trouble, the Starliner, like SpaceX’s Crew Dragon, features powerful abort motors capable of blasting the ship away from its booster at any point from the launch pad to orbit. The capsule then would descend to a parachute-assisted splashdown in the Atlantic Ocean off the East Coast of the United States.

While fully automatic, Wilmore and Williams can manually trigger an abort if necessary. The spacecraft also features two independent systems giving the pilots computer-assisted and direct manual control if major guidance, navigation or computer problems crop up during launch or in orbit.

The Starliner flight marks only the sixth time NASA has put astronauts aboard a new spacecraft for the first time. Jim Free, NASA’s associate administrator for space operations, called the Starliner Crew Flight test, or CFT, “an absolutely critical milestone.”

“The lives of our crew members, Suni Williams and Butch Wilmore, are at stake,” he said. “Let me just remind everybody again, this is a new spacecraft. I’ll also remind you this is a test flight. … We certainly have some unknowns in this mission, we may encounter things we don’t expect. But our job now is to remain vigilant and keep looking for issues.”

While he said he was confident the Starliner is ready to fly, Free said he did not want to “get too far ahead” since the crew has yet to complete a successful mission. But “when we do,” he added, “and when we certify Starliner, the United States will have two unique human space transportations that provide critical redundancy for ISS access.”

Assuming a problem-free launch, it will take the Starliner about 15 minutes to reach its initial orbit. The flight plan calls for Wilmore and Williams to monitor a mostly automated rendezvous with the space station, taking time out twice to manually fly the spacecraft, verifying the crew’s ability to fine-tune the trajectory or step in after a major malfunction.

Approaching the station from behind and below, the astronauts will catch up with the lab complex early Wednesday, docking at the station’s forward port at 12:48 a.m. on May 8.

They’ll be welcomed aboard by Expedition 71 commander Oleg Kononenko and his Soyuz MS-25 crewmates, Nikolai Chub and NASA’s Tracy Dyson, along with NASA Crew 8 commander Matthew Dominick, Michael Barratt, Jeanette Epps and cosmonaut Alexander Grebenkin.

Wilmore and Williams plan to spend a little more than a week aboard the station, transferring 750 pounds of equipment to the lab, powering down the Starliner and making sure it can be used as a “safe haven” for visiting long-duration crews. The current plan calls for undocking on May 15, but that could change depending on weather at the landing site.

Unlike SpaceX’s Crew Dragon, which splashes down in the ocean at the end of a mission, the Starliner is designed to touch down on land, using parachutes and two sets of sequentially inflating airbags to ease the shock of touchdown. For the Crew Flight Test, a May 15 undocking would target landing at White Sands Space Harbor in New Mexico.

But given this is a test flight, NASA will not approve undocking unless winds at the landing site are 6 knots or less. The limit for the actual landing is 10 knots. As a result, NASA may replan for a night landing, when desert winds typically die down, at a different site.

Assuming the flight goes well, NASA managers hope to certify the Starliner for operational crew ferry missions starting next year, launching one Crew Dragon and one Starliner each year to change out space station crew through the program’s retirement at the end of the decade.

Commercial Crew Program marks major shift in human spaceflight

In the wake of the space shuttle’s retirement, NASA awarded two Commercial Crew Program contracts in 2014, one to SpaceX valued at $2.6 billion and the other to Boeing for $4.2 billion, to spur development of independent spacecraft capable of carrying astronauts to and from the International Space Station.

The goal was to end NASA’s post-shuttle reliance on Russia’s Soyuz and to resume launching American astronauts from U.S. soil aboard American rockets and spacecraft. Equally important to NASA: having two independent spacecraft for crew flights to the ISS in case one company’s ferry ship runs into problems that might ground it for an extended period.

The original target date for initial piloted CCP flights was 2017. Funding shortfalls in Congress and technical snags delayed development, including an explosion during a ground test that destroyed a SpaceX Crew Dragon.

But the California rocket builder still managed to kick off piloted flights in May 2020, successfully launching two NASA astronauts on a Crew Dragon test flight to the space station.

Since then, SpaceX has launched eight operational crew rotation flights to the station, three research missions to the lab funded by Houston-based Axiom Space and a purely commercial, two-man, two-woman trip to low-Earth orbit paid for by billionaire pilot and businessman Jared Isaacman. In all, 50 people have flown to orbit aboard Crew Dragons.

It’s been a different story for Boeing’s Starliner.

During an initial unpiloted test flight in December 2019, unexpected software and communications glitches​ prevented a planned rendezvous with the space station. Boeing corrected those problems and opted to carry out a second uncrewed test flight, at its own expense.

But during the second countdown, engineers ran into problems with stuck propulsion system valves​ in the Starliner’s service module. Engineers eventually traced the problem to moisture intrusion and corrosion, triggering another lengthy delay.\

The second Starliner test flight in May 2022 was a success, docking at the space station as planned and returning to Earth with a pinpoint landing. But in the wake of the flight, engineers discovered fresh problems: trouble with parachute harness connectors​ and concern about protective tape wrapped around wiring that could catch fire in a short circuit.

Work to correct those issues pushed the first crewed flight to this year. When all was said and done, Boeing spent more than $1 billion of its own money to pay for the additional test flight and corrective actions.

A critical time for Boeing

The CFT launching comes at a critical time for Boeing given the aftermath of two highly publicized 737 Max crashes in 2018 and 2019 and more recently, the blow out of a cabin door “plug” during an Alaska Airlines flight that has raised fresh questions about the company’s safety culture.

For his part, Wilmore said he didn’t view the Starliner launch in the context of Boeing’s trouble with its airplanes.

“I don’t think it has necessarily anything to do with Boeing and a flight going off,” he said. “They’re all vitally important. This is human spaceflight. That adage you’ve heard since Apollo 13, failure is not an option? That has nothing specifically to do with Boeing or this program. That’s all the things that we do in human spaceflight.

“So, this one is no more or less important than anything else we’re doing,” he said. “It just happens to be the most important one we’re doing right now.”

Williams acknowledged the Starliner’s rocky road to launch. “I’m not going to say it’s been easy. It’s a little bit of (an) emotional roller coaster.”

But, she added, “we knew we would get here eventually. It’s a solid spacecraft. I don’t think I would really want to be in any other place right now.”

Update: Dragon Endurance returned to Earth Tuesday, splashing down off the coast of Florida near Pensacola at 5:47 a.m. EDT (0947 UTC).

A journey of more than half a year orbiting around the world is coming to an end for the four-member team of the SpaceX Crew-7 mission. The Crew Dragon Endurance spacecraft undocked from the International Space Station (ISS) at 11:20 a.m. EDT (1520 UTC) after 197 days.

Commander and NASA astronaut Jasmin Moghbeli and her crew, European Space Agency (ESA) astronaut Andreas Mogensen, Japanese Aerospace Exploration Agency (JAXA) astronaut Satoshi Furukawa and Roscosmos cosmonaut Konstantin Borisov bid farewell to the rest of Expedition 70 during a ceremony on Sunday.

“This has been the adventure of a lifetime. This is something I’ve dreamed about since I was a child and I was afraid I would get up here and might be disappointed and it wouldn’t live up to my expectations,” Moghbeli said. “But the international partnership we have up here and the space station are just incredible. It’s an indication of what we can do when we work together.”

The approaching conclusion of the Crew-7 mission wraps up the first spaceflights for both Moghbeli and Borisov.

“It’s a bittersweet moment. We have been here for over six months, but the time has flown very fast and it’s time to get back,” Borisov said. “I’m really happy that we’ve done all the work we have planned to do. The station is working just fine, all the experiments are going and we know that we are taking over by a great team for continuing into the end of Expedition 70 and into the beginning of Expedition 71.”

During Mogensen’s remarks cap off his second trip to the space station and his first stint as commander of the ISS. At a total of 166 days in that role, he enters the history books as the longest-serving European astronaut commander to date.

Mogensen passed off both a ceremonial key to the station along with the commander duties to Russian cosmonaut Oleg Kononenko. This is Kononenko’s third time to assume command of the ISS.

“On my first mission in 2015, I had the pleasure of flying with Gennady Padalka, who at that time, set the record for 878 days in space. You’ve now surpassed that and you are well on your way to reaching 1,000 days in space, which is an incredible achievement,” Mogensen said. “There is no one more experienced than you when it comes to the International Space Station, so I will be leaving it in probably the best hands possible.”

Kononenko broke Padalka’s record on Feb. 4, 2024 at 2:30:08 a.m. EST (0730:08 UTC) and he is in the middle of his fifth trip to space. He is expected to cross that 1,000-day mark on June 5, 2024.

Crew-7 is now in the midst of a 19-hour journey to splashdown off the coast of Florida at roughly 5:50 a.m. EDT (0950 UTC). NASA and SpaceX will host a teleconference around 7 a.m. EDT (1100 UTC) following splashdown to discuss the conclusion of the mission.

This kicks off a busy week for both NASA and SpaceX. NASA Administrator Bill Nelson is hosting his State of NASA address Monday afternoon along with releasing details of the FY25 budget request.

Meanwhile, SpaceX is preparing for both a mid-week Starlink launch from Florida and the third integrated test flight of its Starship rocket from southern Texas. The latter is waiting for clearance from the Federal Aviation Administration before it can launch.

In in post to social media, SpaceX also noted that while Crew-7 was preparing to undock, it’s also well into the process of training the next quartet who will head to the ISS later this year: Crew-9.

And while Crew-8 was readying for launch and Crew-7 was aboard the orbiting laboratory, Crew-9 was preparing for their mission at SpaceX pic.twitter.com/scr0RM0DlP

— SpaceX (@SpaceX) March 11, 2024

A Russian Progress cargo ship loaded with more than 5,500 pounds of supplies and equipment bound for the International Space Station blasted off from Kazakhstan early Friday, kicking off a two-day orbital chase.

Perched atop a Soyuz 2.1a rocket, the Progress MS-25/86P spacecraft took off from the Baikonur Cosmodrome at 4:25 a.m. EST (2:25 p.m. local time) and slipped into the planned preliminary orbit eight minutes and 45 seconds later.

The Progress then separated, spread its solar wings and set off after the space station in the first stages of a two-day 34-orbit rendezvous. If all goes well, the spacecraft will catch up with the lab complex early Sunday, guiding itself into a docking at the Russian space-facing Poisk module around 6:15 a.m.

The space freighter is delivering 3,423 pounds of spare parts, other equipment and supplies, 88 pounds of nitrogen, 926 pounds of water and 1,135 pounds of propellant used to help maintain the station’s orbit.

The Progress launching was the first of two and possibly three flights to orbit Friday.

SpaceX plans to launch South Korea’s 425 Project satellite from Vandenberg Space Force Base in California at 1:19 p.m. EST. The domestically produced optical-infrared reconnaissance satellite will be followed by four imaging radar spacecraft next year to keep closer tabs on possible military activity in North Korea.

SpaceX is also thought to be gearing up to launch another set of Starlink internet satellites late Friday from the Cape Canaveral Space Force Station in Florida. If both missions get off the ground, they will mark the company’s 90th and 91st Falcon 9 flights so far this year.