The Starliner CST-100 spacecraft being mated on top of ULA’s Atlas V Rocket. Credits: ULA

First Crewed Flight of Boeing’s Starliner Faces Indefinite Delay

Boeing's Starliner crewed flight has been delayed due to a helium leak in its propulsion system, as NASA and engineers evaluate how to proceed with the mission

The inaugural crewed test flight of Boeing’s much-delayed Starliner spacecraft, initially set for launch this Saturday, May 25th, has been postponed indefinitely. This delay comes as engineers work to address a persistent helium leak within the capsule’s propulsion system.

NASA announced this latest setback late Tuesday, after a long press silence, stating that additional time is required to evaluate their options for proceeding with the mission. The leak was discovered in the spacecraft’s service module.

The Starliner CST-100 spacecraft being mated on top of ULA’s Atlas V Rocket. Credits: ULA
The Starliner CST-100 spacecraft being mated on top of ULA’s Atlas V Rocket. Credits: ULA

While NASA did not specify the potential courses of action, multiple sources indicate two options. The first is proceeding with the launch, utilizing the spacecraft as it is now, provided there’s a comprehensive understanding and confidence that the leak won’t worsen. This option could enable a launch as soon as next week.

The second is to remove the capsule from its Atlas V rocket for repairs. This solution, if needed, might push the timeline way more into the future, potentially to late summer.

“The team has been in meetings for two consecutive days, assessing flight rationale, system performance, and redundancy,” NASA said in a statement. “There is still forward work in these areas, and the next possible launch opportunity is still being discussed. NASA will share more details once we have a clearer path forward.”


Delays: not the first, hopefully the last

Delays have been a recurring issue for the Starliner program. An unpiloted test flight in 2019 was cut short, preventing it from reaching the ISS, due to software issues. This forced Boeing to conduct a second demonstration mission.

In 2021, pre-flight checkouts revealed stuck valves in the spacecraft’s propulsion system, prompting further delays to the mission. After overcoming these issues, Starliner successfully completed its first mission to the International Space Station in May 2022.

Additional concerns regarding the spacecraft’s parachutes and flammable tape inside the crew cabin have also contributed to other postponements, pushing the crewed test flight from last summer to this year.

Boeing hopes that a smooth crewed test flight will pave the way for regular six-month crew rotation flights to the ISS beginning next year. The company aims to start transporting astronauts to the ISS under NASA’s Commercial Crew Program, joining SpaceX which is already operational since 2020 with its Crew Dragon Capsule.


How did Boing end up in this situation?

The helium leak was initially detected during the first launch attempt on May 6. Despite this, company’s managers did not deem it significant enough to halt the launch. Ultimately, a separate issue with a pressure regulation valve on the United Launch Alliance (ULA) Atlas V rocket led to the launch being scrubbed.

Technicians returned the Atlas V rocket to its Vertical Integration Facility to replace the faulty valve, aiming for another launch attempt on May 17. However, the date was subsequently pushed to May 21, and then to May 25, as engineers continued to assess the newely-discovered helium leak.

As of now, NASA says that the Atlas V rocket and the Starliner spacecraft remain in ULA’s Vertical Integration Facility pending the next launch opportunity.

Boeing engineers have traced the leak to a flange on a reaction control system thruster within one of the four propulsion pods on the Starliner service module. The propulsion system is pressurized with helium, an inert gas, while the thrusters burn a mixture of hydrazine and nitrogen tetroxide propellants.

Although helium is non-combustible, sufficient gas pressure is required to ensure the propellants reach the thrusters effectively, thus the problem for the launch.

NASA described the helium leak as “stable” in a statement last week, noting it would not pose a risk to the mission if it remained unchanged.

Schedule could be a problem… For everyone

Timing was pitch-perfect for this launch, and won’t be like that for a long time.

ULA has other high-priority missions lined up for the same launch pad, SLC-41, occupied now for Starliner. Additionally, later this summer, ULA plans to launch a US Space Force mission using the last Atlas V rocket for this purpose.

The launch company also aims to launch the second demonstration flight of its new Vulcan Centaur rocket, Atlas V’s replacement, as soon as September pending payload readiness. The flight must launch once again from the same launch pad.

Boeing’s Starliner spacecraft and Atlas V. Credits: ULA
Boeing’s Starliner spacecraft and Atlas V. Credits: ULA

On the ISS side, if NASA and Boeing resolve the issue without needing extensive repairs, the orbiting laboratory could accommodate Starliner’s docking through part of July. Following docking, NASA’s Astronauts Wilmore and Williams are slated to spend at least eight days on the ISS before returning to Earth, landing in the Southwestern United States.

After July thought, scheduling complications arise. The ISS will host multiple visiting crew and cargo vehicles in August, including a new team of astronauts on a SpaceX Dragon spacecraft Mission.

Another possible window for Starliner’s docking could open in late August or early September, before the next SpaceX cargo mission, which will occupy the docking port Starliner needs. The port will be available again in mid-fall.


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Edoardo Giammarino

Edoardo Giammarino

Co-Founder & CEO. Drummer and Red Cross Volunteer, born in 1997. I like analog photography and videomaking. Firmly music-addicted.

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