Why Boeing keeps delaying its Starliner capsule's return from the ISS

Craft arrived with multiple helium leaks and failed thrusters

The Boeing Starliner spacecraft prepares to dock with the International Space Station on June 6. Photo: Nasa

Boeing’s Starliner capsule, long plagued with delays, finally launched on its first crewed mission to the International Space Station two weeks ago, only to face more setbacks with its return having now been postponed multiple times.

Nasa astronauts Butch Wilmore and Suni Williams arrived at the orbiting laboratory on June 6 on a crewed test flight, with the capsule having several technical issues ranging from helium leaks and failed thrusters.

Their return date was initially set for June 19, then June 22, and now has been pushed to June 26 to allow engineers and the astronauts more time to study the spacecraft.

Steve Stich, programme manager of Nasa’s Commercial Crew Programme, said during an online media briefing on Tuesday that they are still analysing the data from the spacecraft’s service module.

The module, which includes the thrusters and life support systems, is detached from the capsule upon re-entry and is burnt up in the atmosphere, so engineers can mostly study it while it is docked at the ISS or mid-flight.

“We're taking our time to understand that service module and the things that we've had happen relative to the helium leaks and also the thruster fail offset docking,” said Mr Stich.

He added that safety was their priority as the team “approach the problems and look towards the return of Butch and Suni”.

This was Starliner’s first crewed test flight in which the astronauts measured spacecraft performance.

A successful flight would bring Boeing closer to beginning flights under Nasa’s Commercial Crew Programme to take astronauts to and back from the ISS – a feat Elon Musk’s SpaceX has already accomplished, having launched eight crews there since 2021.

Is Starliner safe to bring the astronauts home?

A helium leak was detected in Starliner, which has been in development for a decade, before it blasted off into space, but engineers had decided that the leak was not significant enough to delay lift-off.

Mid-flight, while the crew was asleep, two new leaks were detected. These could have compromised the safety of the spacecraft.

Later into the flight, as the capsule approached for a docking at the ISS, five of its 28 reaction-control thrusters – which help fine-tune manoeuvres of a spacecraft – failed.

Since arriving on the ISS, ground control and the astronauts have been assessing the spacecraft's data and carried out a test fire on the thrusters to see if they would start functioning again.

Four out of the five are operating normally again, and will help during the undocking on June 25, with a planned landing in New Mexico on June 26, at 12.51pm UAE time.

“We don't see any scenario where Starliner is not going to be able to bring Butch and Suni home – we really want to work through the remainder of the data,” said Mr Stich.

This is not the first time Starliner has had technical issues, with an uncrewed test flight in 2019 failing to dock with the space station due to a software glitch.

Mr Stich said he sees a silver lining in keeping Starliner docked at the ISS for a while longer, as it could help gather data for the next flight, which is expected to be Boeing Starliner-1, the first commercial crew flight by the company for Nasa.

“I like the fact that we're watching how the vehicle performs thermally, how this space station charges the batteries – we're getting to see those kinds of cycles, which we absolutely need for the increment and subsequent missions,” he said.