Update June 5, 12:06 p.m.: The Boeing Starliner spacecraft successfully separated from the Centaur upper stage of the Atlas 5 rocket. The spacecraft completed its orbital insertion burn and a subsequent burn to circularize its orbit.

The third time was the charm for the first crewed flight of Boeing’s Starliner spacecraft. After two launch attempts on May 6 and June 1 ended with scrubs, the Atlas 5 rocket roared off pad 41 at Cape Canaveral Space Force Station, beginning a more than week-long mission for NASA astronauts Butch Wilmore and Suni Williams.

Liftoff took place on June 5 at 10:52 a.m. EDT (1452 UTC), finally marking the first crewed flight of Boeing’s Starliner spacecraft after years of delays and setbacks. The spacecraft successfully completed its orbital insertion burn about 31 minutes into flight and then circularized its orbit with another burn at T+1 hour and 15 minutes into the mission.

“Two bold NASA astronauts are well on their way on this historic first test flight of a brand-new spacecraft,” said NASA Administrator Bill Nelson, in a statement. “Boeing’s Starliner marks a new chapter of American exploration. Human spaceflight is a daring task – but that’s why it’s worth doing. It’s an exciting time for NASA, our commercial partners, and the future of exploration. Go Starliner, Go Butch and Suni!”

The Wednesday morning launch came following the most recent scrub caused by a countdown computer issue at the launchpad, which United Launch Alliance was able to remedy on Sunday, June 2.

“I really appreciate all the work by the NASA, Boeing, and ULA teams over the last week,” said Steve Stich, manager of NASA’s Commercial Crew Program, in a prelaunch statement. “In particular, the ULA team worked really hard to quickly learn more about these issues, keep our NASA and Boeing teams informed, and protect for this next attempt. We will continue to take it one step at a time.”

Heading into the launch attempt, the 45th Weather Squadron forecast a 90 percent chance of favorable weather at liftoff with only cumulus clouds of possible concern. With some of the sunspots that caused the recent auroras around globe reemerging this week, meteorologists are also keeping an eye on solar activity.

With two good orbital burns behind them, the two-person crew is set to dock with the ISS at about 12:15 p.m. EDT (1615 UTC) on June 6. If all goes well with the mission, the crew will return for a landing in White Sands, New Mexico on June 14.

The launch on June 5 came nearly a month after the original launch date of May 6. That launch was scuttled by an oxygen pressure relief valve on the Altas 5 rocket’s upper stage. The mission stood down for weeks as teams assessed a helium leak on the Starliner’s service module.

Coming out of a planned hold at T-minus 4 minutes during the second launch attempt, the countdown reached the T-minus 3 minutes and 50 seconds when one of the three ground launch sequencer circuit boards failed to synch with the other two, which caused the scrub.

ULA’s President and CEO Tory Bruno said because the mission faced an instantaneous launch window, there wasn’t enough time to properly assess the issue in real time to determine if a fix could be achieved before liftoff.

“The disappointment lasts for about three seconds. And then you just immediately get busy and do your job,” Bruno said while speaking with reporters on Saturday following the scrub.

Mark Nappi, Boeing’s Starliner project manager, said there was disappointment from his team as well, but that quickly turned to resilience.

“You know when you’re playing a game and you get a bad call, you’re a little irritated at first, or a little frustrated at first, but you immediately focus on the next pitch and that’s what our teams do, they’re focused on the next pitch,” Nappi said. “As soon as we went into the launch scrub and launch turnaround, I looked out into the control room and everybody had their heads down, working the procedures to get ready for another attempt.”

The Crew Flight Test of Starliner comes more than four years from SpaceX launching its first astronaut missions using its Crew Dragon spacecraft. Both companies won multi-billion dollar contracts from NASA to provide transporter for its astronauts as part of the Commercial Crew Program.

After the lunch of the Demo-2 mission, SpaceX went on to send more than 50 people to space over the course of 13 flights, 12 of which went to the ISS. Boeing is working to overcome a years-long delay due to numerous technical issues that cost the company more than $1 billion.

Once the CFT mission wraps up, Boeing will work with NASA to finish certifying Starliner for full crew rotation missions, which could begin as soon as the spring of 2025.

Engineers initially were told to set up for another launch try Sunday, at 12:03 p.m. EDT, assuming the problem could be resolved in time. But NASA later announced the team would pass up the Sunday opportunity to give engineers more time to assess the computer issue.

The Starliner’s test flight includes rendezvous and docking with the International Space Station. Based on the lab’s orbit and the Starliner’s ability to to catch up, the next two launch opportunities after Sunday are Wednesday, at 10:52 a.m. EDT, and Thursday, at 10:29 a.m. NASA said the agency would provide an update Sunday.

The Starliner’s crew, commander Barry “Butch” Wilmore and co-pilot Sunita Williams, came within about two hours of launch on May 6, only to be derailed by trouble with a pressure relief valve in their Atlas 5 rocket and a helium leak in the capsule’s propulsion module.

Those problems were resolved and after a few minor snags Saturday, the countdown appeared to be ticking smoothly toward a planned launch at 12:25 p.m. EDT. But 10 seconds after the countdown came out of a planned hold at the T-minus 4-minute mark, the clocks suddenly stopped ticking.

Space station launches are timed for the moment Earth’s rotation carries the pad into alignment with the space station’s orbit, a requirement when trying to rendezvous with a target moving at nearly 5 miles per second. An unplanned hold in the countdown for such missions immediately triggers a minimum 24-hour launch delay.

Tory Bruno, CEO of United Launch Alliance, builder of the Atlas 5 rocket, said the issue Saturday involved one of three networked computer racks in a building at the base of the launch pad. Each rack features multiple systems, including identical circuit boards that operate together as a “ground launch sequencer,” managing the final steps in a countdown.

The GLS computers manage events like the retraction of umbilicals and the firing of explosive bolts that free the rocket from the pad for takeoff, and all three have to be in perfect agreement for a countdown to proceed.

During Saturday’s launch attempt, the countdown ticked down to T-minus 4 minutes and then entered a planned four-hour hold. When the countdown resumed four minutes prior to blastoff, one of the three GLS circuit boards took longer than expected to synch up with the other two. That was enough to trigger an automatic hold at the T-minus 3-minute 50-second mark.

Engineers planned to begin troubleshooting after draining the Atlas 5 of its liquid hydrogen and oxygen propellants and gaining access to the computer room. A decision on how to proceed depended on isolating the problem, replacing and testing any suspect components.

The launch team, while disappointed, took the latest delay in stride.

“You know when you’re playing a game and you get a bad call, you’re a little irritated at first, or a little frustrated at first, but you immediately focus on the next pitch and that’s what our teams do, they’re focused on the next pitch,” said Mark Nappi, Boeing’s Starliner project manager.

“As soon as we went into the launch scrub and launch turnaround, I looked out into the control room and everybody had their heads down, working the procedures to get ready for another attempt tomorrow.”

Said Bruno: “The disappointment lasts for about three seconds. And then you just immediately get busy and do your job. We’ll be back.”

Whenever it takes off, the long-awaited flight will be the first piloted launch of an Atlas 5 and the first for the Atlas family of rockets since astronaut Gordon Cooper took off just a few miles away on the Mercury program’s final flight 61 years ago.

Likewise, it will be the first piloted flight of the Starliner, Boeing’s answer to SpaceX’s Crew Dragon, an already operational, less expensive spacecraft that has carried 50 astronauts, cosmonauts and civilians into orbit in 13 flights, 12 of them to the space station, since an initial piloted test flight in May 2020.

NASA funded development of both spacecraft to ensure the agency would be able to launch crews to the outpost even if one company’s ferry ship was grounded for any reason.

Already running years behind schedule because of budget shortfalls and a variety of technical problems that cost Boeing some $1.4 billion to correct, NASA had hoped to get the Starliner into orbit on May 6. But the launch was scrubbed when United Launch Alliance engineers detected trouble with a pressure-relief valve in the rocket’s Centaur upper stage.

The Atlas 5 was hauled off the pad and back to ULA’s Vertical Integration Facility where the Centaur valve was quickly replaced. But in the wake of the launch scrub, Boeing engineers saw signs of a small helium leak in the Starliner’s propulsion system.

The leak was traced to a flange in plumbing that delivered pressurized helium to drive one specific reaction control system jet in the Starliner’s service module. The leak was characterized as “very small,” but engineers needed to show it would not drastically worsen in flight and cause problems for other thrusters.

After extensive analysis and testing, mission managers concluded the spacecraft could be safely launched as is, saying that even if the leak rate was 100 times worse than so far observed, it would not pose a risk to the crew or the mission. As it turned out, the leak rate remained within acceptable limits Saturday.

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.

NASA is looking at the start of June for its next attempt to launch its astronauts, Butch Wilmore and Suni Williams, on board Boeing’s Starliner spacecraft. The announcement came last Wednesday night in a blog post, stating that June 1 will be the earliest that the Crew Flight Test of Starliner can begin.

The new launch date has a T-0 liftoff of 12:25 p.m. EDT (1625 UTC). There are also backup opportunities available on Sunday, June 2; Wednesday, June 5; and Thursday, June 6.

The May 6 launch date was originally scrubbed about two hours prior to launch due to an issue with an oxygen pressure release valve on the upper stage of United Launch Alliance’s Atlas 5 rocket. That issue was resolved on May 11 after rolling the rocket back to ULA’s Vertical Integration Facility and swapping it out.

However, the launch delay persisted as Boeing was assessing a helium leak connected to a flange on one of the reaction control thrusters on the Starliner spacecraft’s service module. There are a series of thrusters within four chambers on the exterior of the service module called “doghouses.”

The cryogenic helium is used to pressurize the propulsion system on the service module and ensure that the propellant and oxidizer flow as needed to their respective thrusters and the launch abort engines.

The leak was initially believed to be within flight limits and wouldn’t have led to a mission scrub on May 6, which was demonstrated through a pressure test done in the VIF on May 15. But on May 17, NASA and Boeing delayed the mission until May 25, citing the need for Boeing to “develop operational procedures to ensure the system retains sufficient performance capability and appropriate redundancy during the flight.”

The weekend rolled by without any further updates and on May 21, following multiple requests from members of the press for more information, a NASA spokesperson confirmed that May 25 was off the table.

“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,” a NASA spokesperson said.

On May 22, NASA said in a statement that they are still continuing to asses the conditions of the leak as well as the redundancies built into Starliner. A spokesperson noted that unrelated to the helium leak, “teams are in the process of completing a follow-on propulsion system assessment to understand potential helium system impacts on some Starliner return scenarios.”

“There has been a great deal of exceptional analysis and testing over the last two weeks by the joint NASA, Boeing, and ULA teams to replace the Centaur Self Regulating Valve and troubleshoot the Starliner Service Module helium manifold leak,”  said Steve Stich, manager, NASA Commercial Crew Program. “It has been important that we take our time to understand all the complexities of each issue including the redundant capabilities of the Starliner propulsion system and any implications to our Interim Human Rating Certification. We will launch Butch and Suni on this test mission after the entire community has reviewed the teams progress and flight rationale at the upcoming Delta Agency Flight Test Readiness Review.”

A press briefing is now set for Friday, May 24, at 11 a.m. EDT (1500 UTC) to discuss the work done and the path forward to launch. Williams and Wilmore continue to remain in quarantine in Houston, Texas, and have spent the additional weeks conducting further simulator training to prepare for the mission.

Boeing’s Starliner spacecraft was chosen by NASA alongside SpaceX’s Dragon capsule to ferry its astronauts to and from the International Space Station. But Starliner has faced a number of unfortunate hurdles, amid it launch campaign.

The 2019 uncrewed Orbital Test Flight ran into software and communication issues, which led to Boeing footing the bill for a second OFT mission in 2022. The flight was able to safely make it to the ISS and back, but issues were discovered once it was back on the ground.

The CFT mission is designed to demonstrate some of the manual capabilities of the spacecraft that could be used, if the automated system were to have an in-flight issue. A successful CFT would pave the way for the first, full crew rotation mission, Starliner-1, which is currently aiming for launch in the spring of 2025.

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.

Ongoing analysis of a helium leak on Boeing’s Starliner spacecraft forced NASA and Boeing to delay the Crew Flight Test mission further.

A blog post, issued late on Friday afternoon, announced a new target launch date for Starliner CFT with NASA astronauts Butch Wilmore and Suni Williams of no earlier than Saturday, May 25, at 3:09 p.m. EDT (1909 UTC).

The spacecraft will launch atop an Atlas 5 rocket from United Launch Alliance to dock with the International Space Station for a roughly eight-day stay before returning to Earth.

Heading into a May 6 launch attempt, a leak was detected in the pressurization system that allows the fuel and oxidizer on the Starliner’s Service Module (SM) to flow correctly to their designated thrusters when called upon. The SM features 28 reaction control system (RCS) thrusters and 20 orbital maneuvering and attitude control (OMAC) thrusters.

The helium leak was connected to a single RCS thruster and was determined to be within flight limits on May 6.

However, during the countdown, a pressure relief valve on the Atlas 5 rocket’s Centaur upper stage was acting up and the mission was scrubbed about two hours before liftoff. The rocket was rolled back into ULA’s Vertical Integration Facility (VIF) where the valve was replaced, tested and cleared for flight.

While inside the VIF, Boeing decided to further study and test the helium leak to provide greater assurance that it wouldn’t impact the mission.

Teams brought the spacecraft up to flight pressure on May 15 and determined that “the [helium] leak in the flange is stable and would not pose a risk at that level during flight,” NASA and Boeing said in a joint blog post.

The update also noted that “testing also indicated the rest of the thruster system is sealed effectively across the entire service module.”

Helium is pressurized to a certain level during the run-up to launch as well as during the rocket’s ascent in the event that the thrusters and the launch abort engines would be needed for an abort and a quick escape for the astronauts.

Once the spacecraft reaches orbit, it would vent off some of the helium intentionally.

While the testing this week had some positive indications, Boeing and NASA decided to take more time for Boeing “to develop operational procedures to ensure the system retains sufficient performance capability and appropriate redundancy during the flight.”

“As that work proceeds, NASA’s Commercial Crew Program and the International Space Station Program will take the next few days to review the data and procedures to make a final determination before proceeding to flight countdown,” the blog stated.

Spaceflight Now reached out to NASA and Boeing for an interview regarding the update. A NASA spokesperson said there was no briefing planned until the standard pre-launch briefing late next week. Meanwhile, a Boeing spokesperson declined an interview, though presumably, will have a representative participate in the forthcoming briefing. NASA did not respond to requests for interviews.

Following the May 6 launch scrub, and while this work has been ongoing, Wilmore and Williams flew back to Houston, Texas, to be with their families and continue training for the mission. They are due to return to Florida “closer to the new launch date.”

The Starliner spacecraft was selected alongside SpaceX’s Crew Dragon capsule to become the two vehicles NASA would use to transport its astronauts to and from the ISS. Boeing and SpaceX received $4.2 billion and $2.6 billion respectively for the development work and the first six operation missions.

SpaceX launched its uncrewed demonstration mission in 2019 and the two-member crewed Demo-2 flight in May 2020. To date, Dragon has flown 53 people across 13 mission, four of which were non-governmental private flights.

Boeing’s Orbital Flight Test in 2019 ran into multiple issues, including a software problem that prevented it from being able to safely dock to the ISS. The second Orbital Test Flight (OFT-2) was delayed a year due to a corrosion problem in some of the propulsion system valves.

Teams were optimistic about a 2023 launch of the CFT mission, but the mission was delayed until 2024 as they worked through questions concerning the parachutes’ soft links and either mitigated or removed about a mile of flammable tape within the spacecraft.

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.

Boeing’s Starliner spacecraft is going to have a wait a bit longer before its first astronaut mission can take place. Following the decision to scrub the Crew Flight Test mission about two hours prior to liftoff, teams with United Launch Alliance (ULA), Boeing and NASA concluded that more work was needed to prepare the Atlas 5 to launch.

In order to do that, the rocket will need to be rolled back to the Vertical Integration Facility (VIF) at Space Launch Complex 41. The anticipated timeline for the work will push the launch back to no earlier than May 17, according to NASA. The new liftoff time is now 6:16 p.m. EDT (2016 UTC).

During a post-scrub news briefing, ULA President and CEO Tory Bruno discussed an issue with a liquid oxygen self-regulating solenoid relief valve on the Centaur upper stage of the rocket, which created an audible buzzing noise heard by crew working at the launch pad. He said the valve vents pressure from the liquid oxygen tank and is “not dissimilar to many other valves like that,” adding that homeowners “have one in your home on your hot water tank.”

Bruno said that if the valve needed to be replaced, the Atlas 5 rocket would need to make a return to the VIF. However, he noted that the work to replace the valve likely wouldn’t require them to unstack the Starliner spacecraft.

He said because the Centaur upper stage is “a pressure-stabilized stage it has to be either stretched or under pressure to be structurally stable,” and therefore, they could use some tooling to stretch it in the VIF. 

“We’d apply that tooling to support the Centaur and the Starliner on top and then we take off all the pressure and simply remove and replace the valve, re-pressurize it, remove the tooling and then we’d be ready to roll back,” Bruno said. “That procedure takes several days, so it’s unlikely we would be prepared to make another attempt before Sunday.”

Problem valve

Bruno said the issue with the valve was audible to members of the Blue Team, working inside the white room on the launch pad gantry to help the CFT astronauts, Butch Wilmore and Suni Williams, safely get into the Starliner spacecraft and secure the capsule.

Because ULA was preparing to launch a crewed mission, their procedures didn’t allow them to perform the same type of corrective measure that they would have been possible if it was a satellite atop the rocket.

“Once we got the crew off, we cycled the valve and it stopped buzzing. If this were a satellite, that is our standard procedure and the satellite would already be in orbit, but that changes the state of the fueled Centaur and we don’t do that when people are present,” Bruno explained. “And so, our flight rules caused us, called for us to scrub.”

Although cycling the valve stopped the fluttering, the oscillations re-occurred twice as the launch team drained cryogenic propellants from the rocket.

Bruno said that the valve in question is rated for 200,000 cycles (opening and closing). The question that ULA engineers sought to answer as they worked overnight and into the morning was whether they could determine if the valve had reached its life limit.

He said it was difficult to make a thorough determination on the valve as the launch countdown was in progress, which was also partially why they decided to scrub the mission.

“We are inferring the buzzing by looking at accelerometers that are nearby on the RL-10 rocket engines,” Bruno said. “So, what we couldn’t do during the count in real time, and what we are doing now, is going through that data to assess how many cycles were on the valve and whether or not it was fully open or not so that we know if those count as full cycles.”

Bruno said while the issue is relatively rare it is not unheard of and in fact, it is something that they’ve encountered and dealt about a decade ago on the AV-053 mission. That Atlas 5 rocket was launching the $1.1 billion Magnetospheric Multiscale mission for NASA. 

“Prolonged buzzing like this was seen on AV-053, an earlier Atlas launch some time ago. Cycling the valve interrupted it as we expected,” Bruno said. “Three or four other times we have seen short buzzing where it didn’t sustain, but when it reappeared, we cycled the valve and it stopped and never appeared again. So, we have experience four to five times with this, one time with this exact behavior.”

Delayed gratification

The Starliner CFT mission will be the first crewed demonstration of Boeing’s spacecraft, offering NASA the dissimilar redundancy it sought at the onset of its Commercial Crew Program (CCP).

Wilmore and Williams had both suited up in their spacesuits and made it into the capsule by the time the scrub was called at around 8:30 p.m. EDT (0030 UTC). In a post on social media following the decision, NASA astronaut Mike Fincke, the backup pilot for CFT described his support for the decision.

“Even though yesterday’s Starliner launch was postponed, the bravery and professionalism of astronauts Butch and Suni as well as the entire launch team remain as towering as the mighty Atlas 5,” Fincke wrote on X, formerly Twitter. “Our determination underlines every mission’s spirit and we’ll be ready to reach of the stars again soon.”

Even though yesterday's #Starliner launch was postponed, the bravery and professionalism of astronauts Butch and Suni as well as the entire launch team remain as towering as the mighty #AtlasV . Our determination underlines every mission's spirit, and we'll be ready to reach for… pic.twitter.com/RJ87099nrC

— Col. Mike Fincke (@AstroIronMike) May 7, 2024

Williams has been part of the Starliner program for years. Back in 2015, she was one of four astronauts selected to work with Boeing and SpaceX as they developed their vehicles for the the CCP. She was originally named to the Starliner-1 mission in 2018 before being reassigned as the CFT pilot in 2022.

Wilmore was brought onboard as the commander of the CFT mission after former Boeing astronaut Chris Ferguson stepped down from the program in 2020, citing family considerations.

The Starliner program has encountered several challenges over the years, which delayed its crewed launch to four years behind the crewed demonstration of SpaceX’s Crew Dragon. During the post-scrub press conference Monday night, Mark Nappi, Boeing’s CCP program manager, gave his assurance that Starliner remained in good shape and would be ready to fly when the rocket is ready,

NASA officials noted that the schedule for the International Space Station is pretty open this summer, so they are ready to receive Starliner when it makes sense to launch.

“As Suni has told us a couple of times, there was nothing magical about a certain date to go launch on, so we’re taking it one step at a time,” said Steve Stich, NASA’s CCP program manager. “We’re going to launch when we’re ready and fly when it’s safe to do so.”

If the analysis concludes it’s safe to launch the Atlas 5 as is, NASA, Boeing and Atlas 5-builder United Launch Alliance could recycle for a second attempt at 9 p.m. EDT Friday. If the valve has to be replaced, the rocket would have to be hauled back to ULA’s Vertical Integration Facility for repairs, delaying another launch attempt to Sunday or later next week.

An Atlas 5 rocket carrying astronauts for the first time was fueled for blastoff Monday night to boost Boeing’s long-delayed Starliner crew ferry ship into orbit for its first piloted test flight. But trouble with a valve in the rocket’s upper stage forced mission managers to order a scrub just two hours before takeoff.

It was a frustrating disappointment for commander Barry “Butch” Wilmore and co-pilot Sunita Williams, who were in the process of strapping in for launch when the scrub was announced. The moment brought to mind one of Wilmore’s favorite sayings: “you’d rather be on the ground wishing you were in space than in space and wishing you were on the ground.”

It was not immediately clear when Boeing and rocket-builder United Launch Alliance might be able to make another attempt, but engineers will first have to figure out what caused an oxygen relief valve in the rocket’s Centaur upper stage to “chatter” during the late stages of fueling and what might be required to fix it. If the valve has to be replaced, ULA might have to roll the rocket back to its processing facility for repairs.

Already running years behind schedule and more than a billion dollars over budget, the Starliner is Boeing’s answer to SpaceX’s Crew Dragon, an already operational spacecraft that has carried 50 astronauts, cosmonauts and civilians into orbit in 13 flights, 12 of them to the space station.

NASA funded development of both spacecraft to ensure the agency would be able to launch crews to the outpost even if one company’s ferry ship was grounded for any reason. While it’s taken Boeing much longer than expected to ready their ship for crew flights, all systems appeared go for launch from pad 41 at the Cape Canaveral Space Force Station at 10:34 p.m. EDT.

Engineers were in the process of completing propellant loading when the valve problem was detected. After assessing its performance, engineers could not get “comfortable” with its behavior and the launching was called off.

Decked out in Boeing’s dark blue pressure suits, Wilmore and Williams, both veteran Navy test pilots and active-duty astronauts with four earlier spaceflights to their credit, began unstrapping to exit the Starliner and await word on when they’ll get another chance to fly.

The Atlas 5, making its 100th flight, is an extremely reliable rocket with a perfect launch record. The rocket is equipped with a sophisticated emergency fault detection system and the Starliner, like SpaceX’s Crew Dragon, features a “full-envelope” abort system capable of quickly propelling the capsule away from its booster in the event of a major malfunction at any point from the launch pad to orbit.

Whenever it takes off, the Atlas 5 will only need 15 minutes to boost the Starliner into a preliminary orbit. Once in space, the astronauts then will monitor two quick thruster firings to fine-tune the ship’s orbit before taking turns testing the spacecraft’s computer-assisted manual control system.

As with any other space station rendezvous, the Starliner will approach the lab from behind and below, looping up to a point directly ahead of the outpost and then moving in for docking at the Harmony module’s forward port

During final approach, Wilmore and Williams will again test the capsule’s manual controls, making sure future crews can tweak the trajectory or the spacecraft’s orientation at their own discretion if needed.

The Starliner also is equipped with a fully manual backup system that allows the crew to directly command the ship’s thrusters using a joystick-like hand controller, bypassing the spacecraft’s flight computers. Wilmore and Williams will test that system after departing the station and heading back to Earth.

Once docked, Wilmore and Williams will spend a little more than a week with the station’s seven long-duration crew members: cosmonauts Oleg Kononenko, Nikolai Chub and Alexander Grebenkin, along with NASA’s Matthew Dominick, Michael Barratt, Jeanette Epps and Tracy Dyson.

If the Starliner test flight goes well, NASA managers plan to certify it for routine crew rotation flights, launch one Crew Dragon and one Starliner each year to deliver long-duration crew members to the station for six-month tours of duty.

Jim Free, NASA’s associate administrator for space operations, called the Starliner Crew Flight test, or CFT, “an absolutely critical milestone.”

“Let me just remind everybody again, this is a new spacecraft,” he told reporters last week. “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 was up to the task, 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 the ISS access.”

But it hasn’t been easy.

In the wake of the space shuttle’s retirement in 2011, 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 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 finally kicked 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, a software error prevented the ship’s flight computer from loading the correct launch time from its counterpart aboard the Atlas 5.

As a result, a required orbit insertion burn did not happen on time and because of unrelated communications issues, flight controllers were unable to regain control in time to press ahead with a space station rendezvous.

The software problems were addressed after the Starliner’s landing, along with a variety of other issues that came to light in a post-flight review. Boeing opted to carry out a second test flight, at its own expense, but the company ran into into stuck propulsion system valves in the Starliner’s service module. Engineers were unable to resolve the problem and the capsule was taken off its Atlas 5 and hauled back to its processing facility for troubleshooting.

Engineers eventually traced the problem to moisture, presumably from high humidity and torrential rain after rollout to the pad, that chemically reacted with thruster propellant to form corrosion. The corrosion prevented the valves from opening on command.

To clear the way for launch the following May, the valves in a new service module were replaced and the system was modified to prevent water intrusion on the launch pad. 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 from 2023 to 2024. 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.

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.”