Boeing’s Starliner, which transported astronauts to the International Space Station on June 5, encountered several challenges shortly after its launch, including helium leaks and the malfunction of five out of its 28 thrusters. Now, in a new twist, NASA astronaut Butch Wilmore reported hearing an unusual noise from the spacecraft.

Unusual Noise Detected

During a routine check on Saturday, Wilmore detected what he described as a “strange noise” coming through the spacecraft’s speaker.“I’ve got a question about Starliner,” Wilmore radioed Mission Control at Johnson Space Center in Houston. “There’s a strange noise coming through the speaker ... I don’t know what’s making it.” Unsure whether the noise was due to a connection issue between the spacecraft and the station or something else, Wilmore requested that flight controllers listen in to the audio from inside the spacecraft.

Mission Control, after connecting to the spacecraft via a hardline, confirmed they could hear the noise. Wilmore, floating inside Starliner, held his microphone up to the speaker, and shortly after, a distinct pinging sound was audible. “Alright Butch, that one came through,” Mission Control responded. “It was kind of like a pulsing noise, almost like a sonar ping.”

Wilmore then repeated the odd noise for further analysis. “Alright, over to you. Call us if you figure it out,” Mission Control instructed. A recording of the strange sound and Wilmore’s exchange with Mission Control was later shared by Michigan meteorologist Rob Dale.

Source of the Noise Remains Unclear

The source of this eerie, sonar-like noise remains unclear. The Starliner spacecraft, while docked to the International Space Station for nearly three months, communicates with the station through a radio frequency system. Once docked, a hardline umbilical handles the audio transmission.

Such peculiar noises are not unprecedented in space. For instance, during China’s first human spaceflight in 2003, astronaut Yang Liwei reported hearing what resembled an iron bucket being struck by a wooden hammer. It was later discovered that this was due to small deformations in the spacecraft caused by pressure differences.

Ongoing Challenges and Future Plans

While this weekend’s sonar-like sounds are likely benign, they highlight the challenges Boeing and NASA have faced with Starliner’s debut crewed flight. The spacecraft has already experienced issues, including significant helium leaks and malfunctioning thrusters. Recently, NASA decided to return Starliner without its original crew of Wilmore and Sunita Williams due to concerns about its flyability.

Starliner is scheduled to return to Earth autonomously on Friday, September 6. Wilmore and Williams will come back to Earth in February aboard a Crew Dragon spacecraft, which is set to launch later this month with just two astronauts.