human spaceflight

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Boeing will try to fly its troubled Starliner capsule back to Earth next week

Destination desert —

The two astronauts who launched on Starliner will stay behind on the International Space Station.

Boeing's Starliner spacecraft undocks from the International Space Station at the conclusion of an unpiloted test flight in May 2022.

Enlarge / Boeing’s Starliner spacecraft undocks from the International Space Station at the conclusion of an unpiloted test flight in May 2022.

NASA

NASA and Boeing are proceeding with final preparations to undock the Starliner spacecraft from the International Space Station next Friday, September 6, to head for landing at White Sands Space Harbor in southern New Mexico.

Astronauts Butch Wilmore and Suni Williams, who were supposed to return to Earth inside Starliner, will remain behind on the space station after NASA decided last week to conclude the Boeing test flight without its crew on board. NASA officials decided it was too risky to put the astronauts on Starliner after the spacecraft suffered thruster failures during its flight to the space station in early June.

Instead, Wilmore and Williams will come home on a SpaceX Dragon capsule no earlier than February, extending their planned stay on the space station from eight days to eight months. Flying on autopilot, the Starliner spacecraft is scheduled to depart the station at approximately 6: 04 pm EDT (22: 04 UTC) on September 6. The capsule will fire its engines to drop out of orbit and target a parachute-assisted landing in New Mexico at 12: 03 am EDT (04: 03 UTC) on September 7, NASA said in a statement Thursday.

NASA officials completed the second part of a two-day Flight Readiness Review on Thursday to clear the Starliner spacecraft for undocking and landing. However, there are strict weather rules for landing a Starliner spacecraft, so NASA and Boeing managers will decide next week whether to proceed with the return next Friday night or wait for better conditions at the White Sands landing zone.

Over the last few days, flight controllers updated parameters in Starliner’s software to handle a fully autonomous return to Earth without inputs from astronauts flying in the cockpit, NASA said. Boeing has flown two unpiloted Starliner test flights using the same type of autonomous reentry and landing operations. This mission, called the Crew Flight Test (CFT), was the first time astronauts launched into orbit inside a Starliner spacecraft, and was expected to pave the way for future operational missions to rotate four-person crews to and from the space station.

With the Starliner spacecraft unable to complete its test flight as intended, there are fundamental questions about the future of Boeing’s commercial crew program. NASA Administrator Bill Nelson said last week that Boeing’s new CEO, Kelly Ortberg, told him the aerospace company remained committed to Starliner. However, Boeing will be on the hook to pay for the cost of resolving problems with overheating thrusters and helium leaks that hamstrung the CFT mission. Boeing hasn’t made any public statements about the long-term future of the Starliner program since NASA decided to pull its astronauts off the spacecraft for its return to Earth.

Preparing for a contingency

NASA is clearly more comfortable with returning Wilmore and Williams to Earth inside SpaceX’s Dragon capsule, but the change disrupts crew operations at the space station. This week, astronauts have been reconfiguring the interior of a Dragon spacecraft currently docked at the outpost to support six crew members in the event of an emergency evacuation.

With Starliner leaving the space station next week, Dragon will become the lifeboat for Wilmore and Williams. If a fire, a collision with space junk, a medical emergency, or something else forces the crew to leave the complex, the Starliner astronauts will ride home on makeshift seats positioned under the four regular seats inside Dragon, where crews typically put cargo during launch and landing.

At least one of the Starliner astronauts would have to come home without a spacesuit to protect them if the cabin of the Dragon spacecraft depressurized on the descent. This has never happened on a Dragon mission before, but astronauts wear SpaceX-made pressure suits to mitigate the risk. The four astronauts who launched on Dragon have their suits, and NASA officials said a spare SpaceX suit already on the space station fit one of the Starliner astronauts, but they didn’t identify which one.

A pressure suit for the other Starliner crew member will launch on the next Dragon spacecraft—on the Crew-9 mission—set for liftoff on a SpaceX Falcon 9 rocket no earlier than September 24. Starliner’s troubles have also disrupted plans for the Crew-9 mission.

On Friday, NASA announced it would remove two astronauts from the Crew-9 mission, including its commander, Zena Cardman, who is a spaceflight rookie. Veteran astronaut Nick Hague will move from the pilot’s seat to take over as Crew-9 commander. Russian cosmonaut Aleksandr Gorbunov will join him.

NASA and Russia’s space agency, Roscosmos, have an agreement to launch Russian cosmonauts on Dragon missions and US astronauts on Russian Soyuz flights to the station. In exchange for NASA providing a ride for Gorbunov, NASA astronaut Don Pettit will fly to the space station on a Soyuz spacecraft next month.

The so-called “seat swap” arrangement ensures that, even if Dragon or Soyuz were grounded, there is always at least one US astronaut and one Russian cosmonaut on the station overseeing each partner’s segment of the outpost, maintaining propulsion, power generating, pointing control, thermal control, and other critical capabilities to keep the lab operational.

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NASA’s Starliner decision was the right one, but it’s a crushing blow for Boeing

Falling short —

It’s unlikely Boeing can fly all six of its Starliner missions before retirement of the ISS in 2030.

A Starliner spacecraft mounted on top of an Atlas V rocket before an unpiloted test flight in 2022.

Enlarge / A Starliner spacecraft mounted on top of an Atlas V rocket before an unpiloted test flight in 2022.

Ten years ago next month NASA announced that Boeing, one of the agency’s most experienced contractors, won the lion’s share of government money available to end the agency’s sole reliance on Russia to ferry its astronauts to and from low-Earth orbit.

At the time, Boeing won $4.2 billion from NASA to complete development of the Starliner spacecraft and fly a minimum of two, and potentially up to six, operational crew flights to rotate crews between Earth and the International Space Station (ISS). SpaceX won a $2.6 billion contract for essentially the same scope of work.

A decade later the Starliner program finds itself at a crossroads after Boeing learned it will not complete the spacecraft’s first Crew Flight Test with astronauts onboard. NASA formally decided Saturday that Butch Wilmore and Suni Williams, who launched on the Starliner capsule June 5, will instead return to Earth inside a SpaceX Crew Dragon spacecraft. Put simply, NASA isn’t confident enough in Boeing’s spacecraft after it suffered multiple thrusters failures and helium leaks on the way to the ISS.

So where does this leave Boeing with its multibillion contract? Can the company fulfill the breadth of its commercial crew contract with NASA before the space station’s scheduled retirement in 2030? It now seems that there is little chance of Boeing flying six more Starliner missions without a life extension for the ISS. Tellingly, perhaps, NASA has only placed firm orders with Boeing for three Starliner flights once the agency certifies the spacecraft for operational use.

Boeing’s bottom line

Although Boeing did not make an official statement Saturday on its long-term plans for Starliner, NASA Administrator Bill Nelson told reporters he received assurances from Boeing’s new CEO, Kelly Ortberg, that the company remains committed to the commercial crew program. And it will take a significant commitment from Boeing to see it through. Under the terms of its fixed price contract with NASA, the company is on the hook to pay for any expenses to fix the thruster and helium leak problems and get Starliner flying again.

Boeing has already reported $1.6 billion in charges on its financial statements to pay for delays and cost overruns on the Starliner program. That figure will grow as the company will likely need to redesign some elements in the spacecraft’s propulsion system to remedy the problems encountered on the Crew Flight Test (CFT) mission. NASA has committed $5.1 billion to Boeing for the Starliner program, and the agency has already paid out most of that funding.

Boeing's Starliner spacecraft, seen docked at the International Space Station through the window of a SpaceX Dragon spacecraft.

Enlarge / Boeing’s Starliner spacecraft, seen docked at the International Space Station through the window of a SpaceX Dragon spacecraft.

The next step for Starliner remains unclear, and we’ll assess that in more detail later in the story. Had the Starliner test flight ended as expected, with its crew inside, NASA targeted no earlier than August 2025 for Boeing to launch the first of its six operational crew rotation missions to the space station. In light of Saturday’s decision, there’s a high probability Starliner won’t fly with astronauts again until at least 2026.

Starliner safely delivered astronauts Butch Wilmore and Suni Williams to the space station on June 6, a day after their launch from Cape Canaveral Space Force Station, Florida. But five of the craft’s 28 reaction control system thrusters overheated and failed as it approached the outpost. After the failures on the way to the space station, NASA’s engineers were concerned Starliner might suffer similar problems, or worse, when the control jets fired to guide Starliner on the trip back to Earth.

On Saturday, senior NASA leaders decided it wasn’t worth the risk. The two astronauts, who originally planned for an eight-day stay at the station, will now spend eight months on the orbiting research lab until they come back to Earth with SpaceX.

If it’s not a trust problem, is it a judgement issue?

Boeing managers had previously declared Starliner was safe enough to bring Wilmore and Williams home. Mark Nappi, Boeing’s Starliner program manager, regularly appeared to downplay the seriousness of the thruster issues during press conferences throughout Starliner’s nearly three-month mission.

So why did NASA and Boeing engineers reach different conclusions? “I think we’re looking at the data and we view the data and the uncertainty that’s there differently than Boeing does,” said Jim Free, NASA’s associate administrator, and the agency’s most senior civil servant. “It’s not a matter of trust. It’s our technical expertise and our experience that we have to balance. We balance risk across everything, not just Starliner.”

The people at the top of NASA’s decision-making tree have either flown in space before, or had front-row seats to the calamitous decision NASA made in 2003 to not seek more data on the condition of space shuttle Columbia’s left wing after the impact of a block of foam from the shuttle’s fuel tank during launch. This led to the deaths of seven astronauts, and the destruction of Columbia during reentry over East Texas. A similar normalization of technical problems, and a culture of stifling dissent, led to the loss of space shuttle Challenger in 1986.

“We lost two space shuttles as a result there not being a culture in which information could come forward,” Nelson said Saturday. “We have been very solicitous of all of our employees that if you have some objection, you come forward. Spaceflight is risky, even at its safest, and even at its most routine. And a test flight by nature is neither safe nor routine. So the decision to keep Butch and Suni aboard the International Space Station and bring the Starliner home uncrewed is the result of a commitment to safety.”

Now, it seems that culture may truly have changed. With SpaceX’s Dragon spacecraft available to give Wilmore and Williams a ride home, this ended up being a relatively straightforward decision. Ken Bowersox, head of NASA’s space operations mission directorate, said the managers polled for their opinion all supported bringing the Starliner spacecraft back to Earth without anyone onboard.

However, NASA and Boeing need to answer for how the Starliner program got to this point. The space agency approved the launch of the Starliner CFT mission in June despite knowing the spacecraft had a helium leak in its propulsion system. Those leaks multiplied once Starliner arrived in orbit, and are a serious issue on their own that will require corrective actions before the next flight. Ultimately, the thruster problems superseded the seriousness of the helium leaks, and this is where NASA and Boeing are likely to face the most difficult questions moving forward.

NASA astronauts Butch Wilmore and Suni Williams aboard the International Space Station.

Enlarge / NASA astronauts Butch Wilmore and Suni Williams aboard the International Space Station.

Boeing’s previous Starliner mission, known as Orbital Flight Test-2 (OFT-2), successfully launched in 2022 and docked with the space station, later coming back to Earth for a parachute-assisted landing in New Mexico. The test flight achieved all of its major objectives, setting the stage for the Crew Flight Test mission this year. But the spacecraft suffered thruster problems on that flight, too.

Several of the reaction control system thrusters stopped working as Starliner approached the space station on the OFT-2 mission, and another one failed on the return leg of the mission. Engineers thought they fixed the problem by introducing what was essentially a software fix to adjust timing and tolerance settings on sensors in the propulsion system, supplied by Aerojet Rocketdyne.

That didn’t work. The problem lay elsewhere, as engineers discovered during testing this summer, when Starliner was already in orbit. Thruster firings at White Stands, New Mexico, revealed a small Teflon seal in a valve can bulge when overheated, restricting the flow of oxidizer propellant to the thruster. NASA officials concluded there is a chance, however small, that the thrusters could overheat again as Starliner departs the station and flies back to Earth—or perhaps get worse.

“We are clearly operating this thruster at a higher temperature, at times, than it was designed for,” said Steve Stich, NASA’s commercial crew program manager. “I think that was a factor, that as we started to look at the data a little bit more carefully, we’re operating the thruster outside of where it should be operated at.”

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After months of mulling, NASA will decide on Starliner return this weekend

Standby for news —

“The agency flight readiness review is where any formal dissents are presented and reconciled.”

A high-resolution commercial Earth-imaging satellite owned by Maxar captured this view of the International Space Station on June 7 with Boeing's Starliner capsule docked at the lab's forward port (lower right).

Enlarge / A high-resolution commercial Earth-imaging satellite owned by Maxar captured this view of the International Space Station on June 7 with Boeing’s Starliner capsule docked at the lab’s forward port (lower right).

Senior NASA leaders, including the agency’s administrator, Bill Nelson, will meet Saturday in Houston to decide whether Boeing’s Starliner spacecraft is safe enough to ferry astronauts Butch Wilmore and Suni Williams back to Earth from the International Space Station.

The Flight Readiness Review (FRR) is expected to conclude with NASA’s most consequential safety decision in nearly a generation. One option is to clear the Starliner spacecraft to undock from the space station in early September with Wilmore and Williams onboard, as their flight plan initially laid out, or to bring the capsule home without its crew.

As of Thursday, the two veteran astronauts have been on the space station for 77 days, nearly 10 times longer than their planned stay of eight days. Wilmore and Williams were the first people to launch and dock at the space station aboard a Starliner spacecraft, but multiple thrusters failed and the capsule leaked helium from its propulsion system as it approached the orbiting complex on June 6.

That led to months of testing—in space and on the ground—data reviews, and modeling for engineers to try to understand the root cause of the thruster problems. Engineers believe the thrusters overheated, causing Teflon seals to bulge and block the flow of propellant to the small control jets, resulting in losing thrust. The condition of the thrusters improved once Starliner docked at the station when they weren’t repeatedly firing, as they need to do when the spacecraft is flying alone.

However, engineers and managers have not yet reached a consensus about whether the same problem could recur, or get worse, during the capsule’s journey back to Earth. In a worst-case scenario, if too many thrusters fail, the spacecraft would be unable to point in the proper direction for a critical braking burn to guide the capsule back into the atmosphere toward landing.

The suspect thrusters are located on Starliner’s service module, which will perform the deorbit burn and then separate from the astronaut-carrying crew module before reentry. A separate set of small engines will fine-tune Starliner’s trajectory during descent.

If NASA managers decide it’s not worth the risk, Wilmore and Williams would extend their stay on the space station until at least February of next year, when they would return to Earth inside a Dragon spacecraft provided by SpaceX, Boeing’s rival in NASA’s commercial crew program. This would eliminate the threat that thruster problems on the Starliner spacecraft might pose to the crew’s safety during the trip to Earth, but it comes with myriad side effects.

These effects include disrupting crew activities on the space station by bumping two astronauts off the next SpaceX flight, exposing Wilmore and Williams to additional radiation during their time in space, and dealing a debilitating blow to Boeing’s Starliner program.

If Boeing’s capsule cannot return to Earth with its two astronauts, NASA may not certify Starliner for operational crew missions without an additional test flight. In that case, Boeing probably wouldn’t be able to complete all six of its planned operational crew missions under a $4.2 billion NASA contract before the International Space Station is due for retirement in 2030.

FRR-eedom to speak

The Flight Readiness Review at NASA’s Johnson Space Center in Houston will begin Saturday morning. Ken Bowersox, a former astronaut and head of NASA’s Space Operations Mission Directorate, will chair the meeting. NASA Administrator Bill Nelson will participate, too. If there’s no unanimous agreement around the table at the FRR, a final decision on what to do could be elevated above Bowersox to NASA’s associate administrator, Jim Free or to Nelson.

“The agency flight readiness review is where any formal dissents are presented and reconciled,” NASA said in a statement Thursday. “Other agency leaders who routinely participate in launch and return readiness reviews for crewed missions include NASA’s administrator, deputy administrator, associate administrator, various agency center directors, the Flight Operations Directorate, and agency technical authorities.”

NASA has scheduled a press conference for no earlier than 1 pm ET (17: 00 UTC) Saturday to announce the agency’s decision and next steps, the agency said.

Lower-level managers will meet Friday in a so-called Program Control Board to discuss their findings and views before the FRR. At a previous Program Control Board meeting, managers disagreed on whether the agency was ready to sign off that the Starliner spacecraft was safe enough to return its astronauts to Earth.

There’s one new piece of information that engineers will brief to the Program Control Board on Friday:

“Engineering teams have been working to evaluate a new model that represents the thruster mechanics and is designed to more accurately predict performance during the return phase of flight,” NASA said. “This data could help teams better understand system redundancy from undock to service module separation. Ongoing efforts to complete the new modeling, characterize spacecraft performance data, refine integrated risk assessments, and determine community recommendations will fold into the agency-level review.”

After months of mulling, NASA will decide on Starliner return this weekend Read More »

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NASA is about to make its most important safety decision in nearly a generation

Boeing's Starliner spacecraft, seen docked at the International Space Station through the window of a SpaceX Dragon spacecraft.

Enlarge / Boeing’s Starliner spacecraft, seen docked at the International Space Station through the window of a SpaceX Dragon spacecraft.

As soon as this week, NASA officials will make perhaps the agency’s most consequential safety decision in human spaceflight in 21 years.

NASA astronauts Butch Wilmore and Suni Williams are nearly 10 weeks into a test flight that was originally set to last a little more than one week. The two retired US Navy test pilots were the first people to fly into orbit on Boeing’s Starliner spacecraft when it launched on June 5. Now, NASA officials aren’t sure Starliner is safe enough to bring the astronauts home.

Three of the managers at the center of the pending decision, Ken Bowersox and Steve Stich from NASA and Boeing’s LeRoy Cain, either had key roles in the ill-fated final flight of Space Shuttle Columbia in 2003 or felt the consequences of the accident.

At that time, officials misjudged the risk. Seven astronauts died, and the Space Shuttle Columbia was destroyed as it reentered the atmosphere over Texas. Bowersox, Stich, and Cain weren’t the people making the call on the health of Columbia‘s heat shield in 2003, but they had front-row seats to the consequences.

Bowersox was an astronaut on the International Space Station when NASA lost Columbia. He and his crewmates were waiting to hitch a ride home on the next Space Shuttle mission, which was delayed two-and-a-half years in the wake of the Columbia accident. Instead, Bowersox’s crew came back to Earth later that year on a Russian Soyuz capsule. After retiring from the astronaut corps, Bowersox worked at SpaceX and is now the head of NASA’s spaceflight operations directorate.

Stich and Cain were NASA flight directors in 2003, and they remain well-respected in human spaceflight circles. Stich is now the manager of NASA’s commercial crew program, and Cain is now a Boeing employee and chair of the company’s Starliner mission director. For the ongoing Starliner mission, Bowersox, Stich, and Cain are in the decision-making chain.

All three joined NASA in the late 1980s, soon after the Challenger accident. They have seen NASA attempt to reshape its safety culture after both of NASA’s fatal Space Shuttle tragedies. After Challenger, NASA’s astronaut office had a more central role in safety decisions, and the agency made efforts to listen to dissent from engineers. Still, human flaws are inescapable, and NASA’s culture was unable to alleviate them during Columbia‘s last flight in 2003.

NASA knew launching a Space Shuttle in cold weather reduced the safety margin on its solid rocket boosters, which led to the Challenger accident. And shuttle managers knew foam routinely fell off the external fuel tank. In a near-miss, one of these foam fragments hit a shuttle booster but didn’t damage it, just two flights prior to Columbia‘s STS-107 mission.

“I have wondered if some in management roles today that were here when we lost Challenger and Columbia remember that in both of those tragedies, there were those that were not comfortable proceeding,” Milt Heflin, a retired NASA flight director who spent 47 years at the agency, wrote in an email to Ars. “Today, those memories are still around.”

“I suspect Stich and Cain are paying attention to the right stuff,” Heflin wrote.

The question facing NASA’s leadership today? Should the two astronauts return to Earth from the International Space Station in Boeing’s Starliner spacecraft, with its history of thruster failures and helium leaks, or should they come home on a SpaceX Dragon capsule?

Under normal conditions, the first option is the choice everyone at NASA would like to make. It would be least disruptive to operations at the space station and would potentially maintain a clearer future for Boeing’s Starliner program, which NASA would like to become operational for regular crew rotation flights to the station.

But some people at NASA aren’t convinced this is the right call. Engineers still don’t fully understand why five of the Starliner spacecraft’s thrusters overheated and lost power as the capsule approached the space station for docking in June. Four of these five control jets are now back in action with near-normal performance, but managers would like to be sure the same thrusters—and maybe more—won’t fail again as Starliner departs the station and heads for reentry.

NASA is about to make its most important safety decision in nearly a generation Read More »

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SpaceX moving Dragon splashdowns to Pacific to solve falling debris problem

A Crew Dragon spacecraft is seen docked at the International Space Station in 2022. The section of the spacecraft on the left is the pressurized capsule, while the rear section, at right, is the trunk.

Enlarge / A Crew Dragon spacecraft is seen docked at the International Space Station in 2022. The section of the spacecraft on the left is the pressurized capsule, while the rear section, at right, is the trunk.

NASA

Sometime next year, SpaceX will begin returning its Dragon crew and cargo capsules to splashdowns in the Pacific Ocean and end recoveries of the spacecraft off the coast of Florida.

This will allow SpaceX to make changes to the way it brings Dragons back to Earth and eliminate the risk, however tiny, that a piece of debris from the ship’s trunk section might fall on someone and cause damage, injury, or death.

“After five years of splashing down off the coast of Florida, we’ve decided to shift Dragon recovery operations back to the West Coast,” said Sarah Walker, SpaceX’s director of Dragon mission management.

Public safety

In the past couple of years, landowners have discovered debris from several Dragon missions on their property, and the fragments all came from the spacecraft’s trunk, an unpressurized section mounted behind the capsule as it carries astronauts or cargo on flights to and from the International Space Station.

SpaceX returned its first 21 Dragon cargo missions to splashdowns in the Pacific Ocean southwest of Los Angeles. When an upgraded human-rated version of Dragon started flying in 2019, SpaceX moved splashdowns to the Atlantic Ocean and the Gulf of Mexico to be closer to the company’s refurbishment and launch facilities at Cape Canaveral, Florida. The benefits of landing near Florida included a faster handover of astronauts and time-sensitive cargo back to NASA and shorter turnaround times between missions.

The old version of Dragon, known as Dragon 1, separated its trunk after the deorbit burn, allowing the trunk to fall into the Pacific. With the new version of Dragon, called Dragon 2, SpaceX changed the reentry profile to jettison the trunk before the deorbit burn. This meant that the trunk remained in orbit after each Dragon mission, while the capsule reentered the atmosphere on a guided trajectory. The trunk, which is made of composite materials and lacks a propulsion system, usually takes a few weeks or a few months to fall back into the atmosphere and doesn’t have control of where or when it reenters.

Air resistance from the rarefied upper atmosphere gradually slows the trunk’s velocity enough to drop it out of orbit, and the amount of aerodynamic drag the trunk sees is largely determined by fluctuations in solar activity.

SpaceX and NASA, which funded a large portion of the Dragon spacecraft’s development, initially determined the trunk would entirely burn up when it reentered the atmosphere and would pose no threat of surviving reentry and causing injuries or damaging property. However, that turned out to not be the case.

In May, a 90-pound chunk of a SpaceX Dragon spacecraft that departed the International Space Station fell on the property of a “glamping” resort in North Carolina. At the same time, a homeowner in a nearby town found a smaller piece of material that also appeared to be from the same Dragon mission.

These events followed the discovery in April of another nearly 90-pound piece of debris from a Dragon capsule on a farm in the Canadian province of Saskatchewan. SpaceX and NASA later determined the debris fell from orbit in February, and earlier this month, SpaceX employees came to the farm to retrieve the wreckage, according to CBC.

Pieces of a Dragon spacecraft also fell over Colorado last year, and a farmer in Australia found debris from a Dragon capsule on his land in 2022.

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Rocket delivered to launch site for first human flight to the Moon since 1972

Rocket delivered to launch site for first human flight to the Moon since 1972

The central piece of NASA’s second Space Launch System rocket arrived at Kennedy Space Center in Florida this week. Agency officials intend to start stacking the towering launcher in the next couple of months for a mission late next year carrying a team of four astronauts around the Moon.

The Artemis II mission, officially scheduled for September 2025, will be the first voyage by humans to the vicinity of the Moon since the last Apollo lunar landing mission in 1972. NASA astronauts Reid Wiseman, Victor Glover, Christina Koch, and Canadian mission specialist Jeremy Hansen will ride the SLS rocket away from Earth, then fly around the far side of the Moon and return home inside NASA’s Orion spacecraft.

“The core is the backbone of SLS, and it’s the backbone of the Artemis mission,” said Matthew Ramsey, NASA’s mission manager for Artemis II. “We’ve been waiting for the core to get here because all the integrated tests and checkouts that we do have to have the core stage. It has the flight avionics that drive the whole system. The boosters are also important, but the core is really the backbone for Artemis. So it’s a big day.”

The core stage rolled off of NASA’s Pegasus barge at Kennedy early Wednesday, following a weeklong ocean voyage from New Orleans, where Boeing builds the rocket under contract to NASA.

Ramsey told Ars that ground teams hope to begin stacking the rocket’s two powerful solid rocket boosters on NASA’s mobile launcher platform in September. Each booster, supplied by Northrop Grumman, is made of five segments with pre-packed solid propellant and a nose cone. All the pieces for the SLS boosters are at Kennedy and ready for stacking, Ramsey said.

The SLS upper stage, built by United Launch Alliance, is also at the Florida launch site. Now, the core stage is at Kennedy. In August or September, NASA plans to deliver the two remaining elements of the SLS rocket to Florida. These are the adapter structures that will connect the core stage to the upper stage, and the upper stage to the Orion spacecraft.

A heavy-duty crane inside the cavernous Vehicle Assembly Building (VAB) will hoist each segment of the SLS boosters into place on the launch platform. Once the boosters are fully stacked, ground teams will lift the 212-foot (65-meter) core stage vertical in the transfer aisle running through the center of the VAB. A crane will then lower the core stage between the boosters. That could happen as soon as December, according to Ramsey.

Then comes the launch vehicle stage adapter, the upper stage, the Orion stage adapter, and finally, the Orion spacecraft itself.

Moving toward operations

NASA’s inspector general reported in 2022 that NASA’s first four Artemis missions will each cost $4.1 billion. Subsequent documents, including a Government Accountability Office report last year, suggest the expendable SLS core stage is responsible for at least a quarter of the cost for each Artemis flight.

The core stage for Artemis II is powered by four hydrogen-fueled RS-25 engines produced by Aerojet Rocketdyne. Two of the reusable engines for Artemis II have flown on the space shuttle, and the other two RS-25s were built in the shuttle era but never flew. Each SLS launch will put the core stage and its engines in the Atlantic Ocean.

Steve Wofford, who manages the stages office for the SLS program at NASA’s Marshall Space Flight Center, told Ars there are “no major configuration differences” between the core stages for Artemis I and Artemis II. The only minor differences involve instrumentation that NASA wanted on Artemis I to measure pressures, accelerations, vibrations, temperatures, and other parameters on the first flight of the Space Launch System.

“We are still working off some flight observations that we made on Artemis I, but no showstoppers,” Wofford said. “On the first article, the test flight, Artemis I, we really loaded it up. That’s a golden opportunity to learn as much as you can about the vehicle and the flight regime, and anchor all your models… As you progress, you need less and less of that. So Core Stage 2 will have less development flight instrumentation than Core Stage 1, and then Core Stage 3 will have less still.”

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NASA nears decision on what to do with Boeing’s troubled Starliner spacecraft

Boeing's Strainer spacecraft is seen docked at the International Space Station in this picture taken July 3.

Enlarge / Boeing’s Strainer spacecraft is seen docked at the International Space Station in this picture taken July 3.

The astronauts who rode Boeing’s Starliner spacecraft to the International Space Station last month still don’t know when they will return to Earth.

Astronauts Butch Wilmore and Suni Williams have been in space for 51 days, six weeks longer than originally planned, as engineers on the groundwork through problems with Starliner’s propulsion system.

The problems are twofold. The spacecraft’s reaction control thrusters overheated, and some of them shut off as Starliner approached the space station June 6. A separate, although perhaps related, problem involves helium leaks in the craft’s propulsion system.

On Thursday, NASA and Boeing managers said they still plan to bring Wilmore and Williams home on the Starliner spacecraft. In the last few weeks, ground teams completed testing of a thruster on a test stand at White Sands, New Mexico. This weekend, Boeing and NASA plan to fire the spacecraft’s thrusters in orbit to check their performance while docked at the space station.

“I think we’re starting to close in on those final pieces of flight rationale to make sure that we can come home safely, and that’s our primary focus right now,” Stich said.

The problems have led to speculation that NASA might decide to return Wilmore and Williams to Earth in a SpaceX Crew Dragon spacecraft. There’s one Crew Dragon currently docked at the station, and another one is slated to launch with a fresh crew next month. Steve Stich, manager of NASA’s commercial crew program, said the agency has looked at backup plans to bring the Starliner crew home on a SpaceX capsule, but the main focus is still to have the astronauts fly home aboard Starliner.

“Our prime option is to complete the mission,” Stich said. “There are a lot of good reasons to complete this mission and bring Butch and Suni home on Starliner. Starliner was designed, as a spacecraft, to have the crew in the cockpit.”

Starliner launched from Cape Canaveral Space Force Station in Florida on June 5. Wilmore and Williams are the first astronauts to fly into space on Boeing’s commercial crew capsule, and this test flight is intended to pave the way for future operational flights to rotate crews of four to and from the International Space Station.

Once NASA fully certifies Starliner for operational missions, the agency will have two human-rated spaceships for flights to the station. SpaceX’s Crew Dragon has been flying astronauts since 2020.

Tests, tests, and more tests

NASA has extended the duration of the Starliner test flight to conduct tests and analyze data in an effort to gain confidence in the spacecraft’s ability to safely bring its crew home and to better understand the root causes of the overheating thrusters and helium leaks. These problems are inside Starliner’s service module, which is jettisoned to burn up in the atmosphere during reentry, while the reusable crew module, with the astronauts inside, parachutes to an airbag-cushioned landing.

The most important of these tests was a series of test-firings of a Starliner thruster on the ground. This thruster was taken from a set of hardware slated to fly on a future Starlink mission, and engineers put it through a stress test, firing it numerous times to replicate the sequence of pulses it would see in flight. The testing simulated two sequences of flying up to the space station, and five sequences the thruster would execute during undocking and a deorbit burn for return to Earth.

“This thruster has seen quite a bit of pulses, maybe even more than what we would anticipate we would see during a flight, and more aggressive in terms of two uphills and five downhills,” Stich said. “What we did see in the thruster is the same kind of thrust degradation that we’re seeing on orbit. In a number of the thrusters (on Starliner), we’re seeing reduced thrust, which is important.”

Starliner’s flight computer shut off five of the spacecraft’s 28 reaction control system thrusters, produced by Aerojet Rocketdyne, during the rendezvous with the space station last month. Four of the five thrusters were recovered after overheating and losing thrust, but officials have declared one of the thrusters unusable.

The thruster tested on the ground showed similar behavior. Inspections of the thruster at White Sands showed bulging in a Teflon seal in an oxidizer valve, which could restrict the flow of nitrogen tetroxide propellant. The thrusters, each generating about 85 pounds of thrust, consume the nitrogen tetroxide, or NTO, oxidizer and mix it with hydrazine fuel for combustion.

A poppet valve, similar to an inflation valve on a tire, is designed to open and close to allow nitrogen tetroxide to flow into the thruster.

“That poppet has a Teflon seal at the end of it,” Nappi said. “Through the heating and natural vacuum that occurs with the thruster firing, that poppet seal was deformed and actually bulged out a little bit.”

Stich said engineers are evaluating the integrity of the Teflon seal to determine if it could remain intact through the undocking and deorbit burn of the Starliner spacecraft. The thrusters aren’t needed while Starliner is attached to the space station.

“Could that particular seal survive the rest of the flight? That’s the important part,” Stich said.

NASA nears decision on what to do with Boeing’s troubled Starliner spacecraft Read More »

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NASA update on Starliner thruster issues: This is fine

Boeing's Starliner spacecraft on final approach to the International Space Station last month.

Enlarge / Boeing’s Starliner spacecraft on final approach to the International Space Station last month.

Before clearing Boeing’s Starliner crew capsule to depart the International Space Station and head for Earth, NASA managers want to ensure the spacecraft’s problematic control thrusters can help guide the ship’s two-person crew home.

The two astronauts who launched June 5 on the Starliner spacecraft’s first crew test flight agree with the managers, although they said Wednesday that they’re comfortable with flying the capsule back to Earth if there’s any emergency that might require evacuation of the space station.

NASA astronauts Butch Wilmore and Suni Williams were supposed to return to Earth weeks ago, but managers are keeping them at the station as engineers continue probing thruster problems and helium leaks that have plagued the mission since its launch.

“This is a tough business that we’re in,” Wilmore, Starliner’s commander, told reporters Wednesday in a news conference from the space station. “Human spaceflight is not easy in any regime, and there have been multiple issues with any spacecraft that’s ever been designed, and that’s the nature of what we do.”

Five of the 28 reaction control system thrusters on Starliner’s service module dropped offline as the spacecraft approached the space station last month. Starliner’s flight software disabled the five control jets when they started overheating and losing thrust. Four of the thrusters were later recovered, although some couldn’t reach their full power levels as Starliner came in for docking.

Wilmore, who took over manual control for part of Starliner’s approach to the space station, said he could sense the spacecraft’s handling qualities diminish as thrusters temporarily failed. “You could tell it was degraded, but still, it was impressive,” he said. Starliner ultimately docked to the station in autopilot mode.

In mid-June, the Starliner astronauts hot-fired the thrusters again, and their thrust levels were closer to normal.

“What we want to know is that the thrusters can perform; if whatever their percentage of thrust is, we can put it into a package that will get us a deorbit burn,” said Williams, a NASA astronaut serving as Starliner’s pilot. “That’s the main purpose that we need [for] the service module: to get us a good deorbit burn so that we can come back.”

These small thrusters aren’t necessary for the deorbit burn itself, which will use a different set of engines to slow Starliner’s velocity enough for it to drop out of orbit and head for landing. But Starliner needs enough of the control jets working to maneuver into the proper orientation for the deorbit firing.

This test flight is the first time astronauts have flown in space on Boeing’s Starliner spacecraft, following years of delays and setbacks. Starliner is NASA’s second human-rated commercial crew capsule, and it’s poised to join SpaceX’s Crew Dragon in a rotation of missions ferrying astronauts to and from the space station through the rest of the decade.

But first, Boeing and NASA need to safely complete the Starliner test flight and resolve the thruster problems and helium leaks plaguing the spacecraft before moving forward with operational crew rotation missions. There’s a Crew Dragon spacecraft currently docked to the station, but Steve Stich, NASA’s commercial crew program manager, told reporters Wednesday that, right now, Wilmore and Williams still plan to come home on Starliner.

“The beautiful thing about the commercial crew program is that we have two vehicles, two different systems, that we could use to return crew,” Stich said. “So we have a little bit more time to go through the data and then make a decision as to whether we need to do anything different. But the prime option today is to return Butch and Suni on Starliner. Right now, we don’t see any reason that wouldn’t be the case.”

Mark Nappi, Boeing’s Starliner program manager, said officials identified more than 30 actions to investigate five “small” helium leaks and the thruster problems on Starliner’s service module. “All these items are scheduled to be completed by the end of next week,” Nappi said.

“It’s a test flight, and the first with crew, and we’re just taking a little extra time to make sure that we understand everything before we commit to deorbit,” Stich said.

NASA update on Starliner thruster issues: This is fine Read More »

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NASA orders more tests on Starliner, but says crew isn’t stranded in space

Boeing's Starliner spacecraft is seen docked at the International Space Station on June 13.

Enlarge / Boeing’s Starliner spacecraft is seen docked at the International Space Station on June 13.

NASA and Boeing officials pushed back Friday on headlines that the commercial Starliner crew capsule is stranded at the International Space Station but said they need more time to analyze data before formally clearing the spacecraft for undocking and reentry.

Two NASA astronauts, commander Butch Wilmore and pilot Suni Williams, will spend at least a few more weeks on the space station as engineers on the ground conduct thruster tests to better understand issues with the Starliner propulsion system in orbit. Wilmore and Williams launched June 5 aboard an Atlas V rocket and docked at the station the next day, completing the first segment of Starliner’s first test flight with astronauts.

NASA managers originally planned for the Starliner spacecraft to remain docked at the space station for at least eight days, although they left open the possibility of a mission extension. The test flight is now likely to last at least a month and a half, and perhaps longer, as engineers wrestle with helium leaks and thruster glitches on Starliner’s service module.

Batteries on this Starliner spacecraft were initially only certified for a 45-day mission duration, but NASA officials said they are looking at extending the limit after confirming the batteries are functioning well.

“We have the luxury of time,” said Ken Bowersox, associate administrator for NASA’s space operations mission directorate. “We’re still in the middle of a test mission. We’re still pressing forward.”

Previously, NASA and Boeing officials delayed Starliner’s reentry and landing from mid-June, then from June 26, and now they have bypassed a potential landing opportunity in early July. Last week, NASA said in a statement that the agency’s top leadership will meet to formally review the readiness of Starliner for reentry, something that wasn’t part of the original plan.

“We’re not stuck on ISS”

Steve Stich, manager of NASA’s commercial crew program, said Friday that he wanted to clear up “misunderstandings” that led to headlines claiming the Starliner spacecraft was stuck or stranded at the space station.

“I want to make it very clear that Butch and Suni are not stranded in space,” Stich said. “Our plan is to continue to return them on Starliner and return them home at the right time. We have a little bit more work to do to get there for the final return, but they’re safe on (the) space station.”

With Starliner docked, the space station currently hosts three different crew spacecraft, including SpaceX’s Crew Dragon and Russia’s Soyuz. There are no serious plans under consideration to bring Wilmore and Williams home on a different spacecraft.

“Obviously, we have the luxury of having multiple vehicles, and we work contingency plans for lots of different cases, but right now, we’re really focused on returning Butch and Suni on Starliner,” Stich said.

“We’re not stuck on the ISS,” said Mark Nappi, Boeing’s vice president in charge of the Starliner program. “It’s pretty painful to read the things that are out there. We’ve gotten a really good test flight that’s been accomplished so far, and it’s being viewed rather negatively.”

Stich said NASA officials should have “more frequent interaction” with reporters to fill in gaps of information on the Starliner test flight. NASA’s written updates are not always timely, and often lack details and context.

NASA officials have cleared the Starliner spacecraft for an emergency return to Earth if astronauts need to evacuate the space station for safety or medical reasons. But NASA hasn’t yet approved Starliner for reentry and landing under “nominal” conditions.

“When it is a contingency situation, we’re ready to put the crew on the spacecraft and bring them home as a lifeboat,” Bowersox said. “For the nominal entry, we want to look at the data more before we make the final call to put the crew aboard the vehicle, and it’s a serious enough call that we’ll bring the senior management team together (for approval).”

NASA orders more tests on Starliner, but says crew isn’t stranded in space Read More »

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Countdown begins for third try launching Boeing’s Starliner crew capsule

Going today? —

Astronauts Butch Wilmore and Suni Williams have been in prelaunch quarantine for six weeks.

Astronauts Suni Williams and Butch Wilmore, wearing their Boeing spacesuits, leave NASA's crew quarters during a launch attempt May 6.

Enlarge / Astronauts Suni Williams and Butch Wilmore, wearing their Boeing spacesuits, leave NASA’s crew quarters during a launch attempt May 6.

Fresh off repairs at the launch pad in Florida, United Launch Alliance engineers restarted the countdown overnight for the third attempt to send an Atlas V rocket and Boeing’s Starliner spacecraft on a test flight to the International Space Station.

NASA astronauts Butch Wilmore and Suni Williams were expected to awake early Wednesday, put on their blue pressure suits, and head to the launch pad at Cape Canaveral Space Force Station to board the Starliner capsule on top of the 172-foot-tall Atlas V rocket.

Once more through the door

Wilmore and Williams have done this twice before in hopes of launching into space on the first crew flight of Boeing’s Starliner spacecraft. A faulty valve on the Atlas V rocket prevented liftoff May 6, then engineers discovered a helium leak on the Starliner capsule itself. After several weeks of troubleshooting, NASA and Boeing officials decided to proceed with another launch attempt Saturday.

Everything seemed to be coming together for Boeing’s long-delayed crew test flight until a computer problem triggered an automatic hold in the countdown less than four minutes before liftoff. Technicians from United Launch Alliance (ULA), the Atlas V rocket’s builder and operator, traced the problem to a failed power distribution source connected to a ground computer responsible for controlling the final phase of the countdown.

The instantaneous launch opportunity Wednesday is set for 10: 52 am EDT (14: 52 UTC), when the launch site at Cape Canaveral passes underneath the space station’s orbital plane. Forecasters predict a 90 percent chance of good weather for launch. You can watch NASA’s live coverage in the video embedded below.

The countdown began late Tuesday night with the power-up of the Atlas V rocket, which was set to be filled with cryogenic liquid hydrogen and liquid oxygen propellants around 5 am EDT (09: 00 UTC). Kerosene fuel was loaded into the Atlas V’s first-stage booster prior to the mission’s first launch attempt in early May.

The two Starliner astronauts departed crew quarters at NASA’s Kennedy Space Center for the 20-minute drive to the launch pad, where they arrived shortly before 8 am EDT (12: 00 UTC) to climb into their seats inside the Starliner capsule. After pressure checks of the astronauts’ suits and Starliner’s crew cabin, ground teams will evacuate the pad about an hour before launch.

Assuming all systems are “go” for launch, the Atlas V will ignite its Russian-made RD-180 main engine and two solid-fueled boosters to vault away from Cape Canaveral and head northeast over the Atlantic Ocean. Wilmore and Williams will be not only the first people to fly in space on Boeing’s Starliner, but also the first astronauts to ride on an Atlas V rocket, which has flown 99 times before with satellites for the US military, NASA, and commercial customers.

The rocket’s Centaur upper stage will deploy Starliner into space around 15 minutes after liftoff. A critical burn by Starliner’s engines will happen around 31 minutes into the flight to finish the task of placing it into low-Earth orbit, setting it up for an automated docking at the International Space Station at 12: 15 pm EDT (16: 15 UTC) Thursday.

The two-person crew will stay on the station for at least a week, although a mission extension is likely if the mission is going well. Officials may decide to extend the mission to complete more tests or to wait for optimal weather conditions at Starliner’s primary and backup landing sites in New Mexico and Arizona. When weather conditions look favorable, Starliner will undock from the space station and head for landing under parachutes.

The crew test flight is a prerequisite to Boeing’s crew capsule becoming operational for NASA, which awarded multibillion-dollar commercial crew contracts to Boeing and SpaceX in 2014. SpaceX’s Crew Dragon started flying astronauts in 2020, while Boeing’s project has been stricken by years of delays.

Wilmore and Williams, both former US Navy test pilots, will take over manual control of Starliner at several points during the test flight. They will evaluate the spacecraft’s flying characteristics and accommodations for future flights, which will carry four astronauts at a time rather than two.

“The expectation from the media should not be perfection,” Wilmore told Ars earlier this year. “This is a test flight. Flying and operating in space is hard. It’s really hard, and we’re going to find some stuff. That’s expected. It’s the first flight where we are integrating the full capabilities of this spacecraft.”

Countdown begins for third try launching Boeing’s Starliner crew capsule Read More »

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Boeing’s Starliner test flight scrubbed again after hold in final countdown

Hold Hold Hold —

The ground launch sequencer computer called a hold at T-minus 3 minutes, 50 seconds.

NASA commander Butch Wilmore exits the Starliner spacecraft Saturday following the scrubbed launch attempt.

Enlarge / NASA commander Butch Wilmore exits the Starliner spacecraft Saturday following the scrubbed launch attempt.

A computer controlling the Atlas V rocket’s countdown triggered an automatic hold less than four minutes prior to liftoff of Boeing’s commercial Starliner spacecraft Saturday, keeping the crew test flight on the ground at least a few more days.

NASA astronauts Butch Wilmore and Suni Williams were already aboard the spacecraft when the countdown stopped due to a problem with a ground computer. “Hold. Hold. Hold,” a member of Atlas V launch team called out on an audio feed.

With the hold, the mission missed an instantaneous launch opportunity at 12: 25 pm EDT (16: 25 UTC), and later Saturday, NASA announced teams will forego a launch opportunity Sunday. The next chance to send Starliner into orbit will be 10: 52 am EDT (14: 52 UTC) Wednesday. The mission has one launch opportunity every one-to-two days, when the International Space Station’s orbital track moves back into proper alignment with the Atlas V rocket’s launch pad in Florida.

Wilmore and Williams will take the Starliner spacecraft on its first crew flight into low-Earth orbit. The capsule will dock with the International Space Station around a day after launch, spend at least a week there, then return to a parachute-assisted landing at one of two landing zones in New Mexico or Arizona. Once operational, Boeing’s Starliner will join SpaceX’s Crew Dragon capsule to give NASA two independent human-rated spacecraft for transporting astronauts to and from the space station.

It’s been a long road to get here with the Starliner spacecraft, and there’s more work to do before the capsule’s long-delayed first flight with astronauts.

Technicians from United Launch Alliance, builder of the Atlas V rocket, will begin troubleshooting the computer glitch at the launch pad Saturday evening, after draining propellant from the launch vehicle. Early indications suggest that a card in one of three computers governing the final minutes of the Atlas V’s countdown didn’t boot up as quickly as anticipated.

“You can imagine a large rack that is a big computer where the functions of the computer as a controller are broken up separately into individual cards or printed wire circuit boards with their logic devices,” said Tory Bruno, ULA’s president and CEO. “They’re all standalone, but together it’s an integrated controller.”

The computers are located at the launch pad inside a shelter near the base of the Atlas V rocket at Cape Canaveral Space Force Station. All three computers must be fully functioning in the final phase of the countdown to ensure triple redundancy. At the moment of liftoff, these computers control things like retracting umbilical lines and releasing bolts holding the rocket to its mobile launch platform.

Two of the computers activated as the final countdown sequence began at T-minus 4 minutes. A single card in the third computer took about six more seconds to come online, although it did boot up eventually, Bruno said.

“Two came up normally and the third one came up, but it was slow to come up, and that tripped a red line,” he said.

A disappointment

Wilmore and Williams, both veteran astronauts and former US Navy test pilots, exited the Starliner spacecraft with the help of Boeing’s ground team. They returned to NASA crew quarters at the nearby Kennedy Space Center to wait for the next launch attempt.

The schedule for the next try will depend on what ULA workers find when they access the computers at the launch pad. Officials initially said they could start another launch countdown early Sunday if they found a simple solution to the computer problem, such as swapping out a faulty card. The computers are networked together, but the architecture is designed with replaceable cards, each responsible for different functions during the countdown, to allow for a quick fix without having to replace the entire unit, Bruno said.

United Launch Alliance's Atlas V rocket and Boeing's Starliner spacecraft at Cape Canaveral Space Force Station, Florida.

Enlarge / United Launch Alliance’s Atlas V rocket and Boeing’s Starliner spacecraft at Cape Canaveral Space Force Station, Florida.

Later Saturday, NASA announced the launch won’t happen Sunday, giving teams additional time to assess the computer issue. The next launch opportunities are Wednesday and Thursday.

Bruno said ULA’s engineers suspect a hardware problem or a network communication glitch caused the computer issue during Saturday’s countdown. That is what ULA’s troubleshooting team will try to determine overnight. NASA said officials will share another update Sunday.

If it doesn’t get off the ground by Thursday, the Starliner test flight could face a longer delay to allow time for ULA to change out limited-life batteries on the Atlas V rocket. Bruno said the battery swap would take about 10 days.

Saturday’s aborted countdown was the latest in a string of delays for Boeing’s Starliner program. The spacecraft’s first crew test flight is running seven years behind the schedule Boeing announced when NASA awarded the company a $4.2 billion contract for the crew capsule in 2014. Put another way, Boeing has arrived at this moment nine years after the company originally said the spacecraft could be operational, when the program was first announced in 2010.

“Of course, this is emotionally disappointing,” said Mike Fincke, a NASA astronaut and a backup to Wilmore and Williams on the crew test flight. “I know Butch and Suni didn’t sound disappointed when we heard them on the loops, and it’s because it comes back to professionalism.”

NASA and Boeing were on the cusp of launching the Starliner test flight May 6, but officials called off the launch attempt due to a valve problem on the Atlas V rocket. Engineers later discovered a helium leak on the Starliner spacecraft’s service module, but managers agreed to proceed with the launch Saturday if the leak did not worsen during the countdown.

A check of the helium system Saturday morning showed the leak rate had decreased from a prior measurement, and it was no longer a constraint to launch. Instead, a different problem emerged to keep Starliner on Earth.

“Everybody is a little disappointed, but you kind of roll your sleeves up and get right back to work,” said Steve Stich, manager of NASA’s commercial crew program.

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Boeing’s Starliner capsule poised for second try at first astronaut flight

Boeing's Starliner spacecraft sits on top of a United Launch Alliance Atlas V rocket at Cape Canaveral Space Force Station, Florida.

Enlarge / Boeing’s Starliner spacecraft sits on top of a United Launch Alliance Atlas V rocket at Cape Canaveral Space Force Station, Florida.

NASA and Boeing officials are ready for a second attempt to launch the first crew test flight on the Starliner spacecraft Saturday from Cape Canaveral Space Force Station, Florida.

Liftoff of Boeing’s Starliner capsuled atop a United Launch Alliance Atlas V rocket is set for 12: 25 pm EDT (16: 25 UTC). NASA commander Butch Wilmore and pilot Suni Williams, both veteran astronauts, will take the Starliner spacecraft on its first trip into low-Earth orbit with a crew on board.

You can watch NASA TV’s live coverage of the countdown and launch below.

The first crew flight on a new spacecraft is not an everyday event. Starliner is the sixth orbital-class crew spacecraft in the history of the US space program, following Mercury, Gemini, Apollo, the space shuttle, and SpaceX’s Crew Dragon. NASA signed a $4.2 billion contract with Boeing in 2014 to develop Starliner, but the project is running years behind schedule and has cost Boeing nearly $1.5 billion in cost overruns. SpaceX, meanwhile, won a contract at the same time as Boeing and started launching astronauts on the Crew Dragon four years ago this week.

Now, it is finally Starliner’s turn. A successful crew test flight would set the stage for six operational Starliner flights to ferry astronauts to and from the International Space Station (ISS).

Assuming the test flight gets off the ground Saturday, the spacecraft is due for docking at the ISS at 1: 50 pm EDT (17: 50 UTC) Sunday to begin a stay of at least eight days. Once managers are satisfied the mission has achieved all its planned test objectives, and pending good weather conditions in Starliner’s landing zone in the western United States, the spacecraft will depart the station and return to Earth for a parachute-assisted touchdown. If the mission takes off on Saturday, the earliest nominal landing date would be Monday, June 10.

Wilmore and Williams have been here before. On May 6, the astronauts were strapped into their seats inside Starliner’s cockpit awaiting takeoff on a flight to the International Space Station. A valve malfunction on the Atlas V rocket prevented launch that day, and officials subsequently discovered a helium leak on Starliner’s service module that delayed the mission until this weekend.

Flying as-is

After weeks of reviews and analysis, managers determined Starliner is safe to fly as-is with the leak. The spacecraft uses helium gas to pressurize its propulsion system and push hydrazine and nitrogen tetroxide propellants from internal tanks to the capsule’s maneuvering thrusters.

“When we looked at this problem, it didn’t come down to trades,” said Mark Nappi, Boeing’s vice president and program manager for Starliner. “It came down to: Is it safe or not? And it is safe, and that is why we determined that we can fly with what we have.”

Ground teams traced the leak to a flange on one of four doghouse-shaped propulsion pods around the perimeter of the Starliner spacecraft’s service module. In a worst-case scenario, if the condition grew worse during the flight, ground controllers could isolate it by closing the manifold feeding the leak. If the leak doesn’t worsen, engineers are confident they can manage it with no major impacts to the mission.

“We looked really hard at what our options were with this particular flange,” said Steve Stich, manager of NASA’s commercial crew program, which oversees the agency’s contract with Boeing. The flange has a helium conduit and lines for the spacecraft’s toxic fuel and oxidizer, which makes a repair “problematic,” Stich said.

Starliner commander Butch Wilmore and pilot Suni Williams arrived back at NASA's Kennedy Space Center earlier this week to prepare for launch.

Enlarge / Starliner commander Butch Wilmore and pilot Suni Williams arrived back at NASA’s Kennedy Space Center earlier this week to prepare for launch.

In order to safely fix the leak, which officials believe is likely caused by a defective seal, ground teams would have to disconnect the capsule from the Atlas V rocket, take it back to a hangar, drain its propellant tanks. This would probably push back the long-delayed Starliner test flight until late this year.

But the leak is relatively small and stable. “It’s about a half-pound per day out of 50 pounds of total capability in the tank,” Stich said.

“In our case, we have margin in the helium tank, and we’ve looked really hard to understand that margin and to understand the worst cases, and we took the time to go through that data,” Stich said. “We really think we can manage this leak, both by looking at it before the launch, and then if it got bigger in flight, we could manage it.”

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