When will Sunita Williams and Butch Wilmore finally return to Earth?

Sunita Williams and Butch Wilmore has been aboard the ISS since June 6, after the Boeing Starliner experienced technical issues that delayed their return

The much-anticipated return of National Aeronautics and Space Administration (Nasa) astronauts Sunita Williams and Butch Wilmore has been the subject of widespread curiosity. During a call from the International Space Station (ISS), the astronauts reassured the public of their confidence in a safe journey back to Earth, despite the technical hiccups with their spacecraft.

The duo has been aboard the ISS since June 6, after the Boeing Starliner experienced technical issues that delayed their return. Originally set to stay for just a week, their mission was extended due to thruster malfunctions and helium leaks discovered mid-flight.

For now, Nasa has not set a definitive return date. Officials are eyeing a ‘late July’ return. Steve Stich, Nasa’s commercial crew program manager, optimistically suggested, “Some of the data suggests maybe it’s by the end of July, but we’ll just follow the data each step at a time.”

During the press call, when asked about their faith in the Starliner team and the spacecraft, mission commander Wilmore said, “We’re absolutely confident.” Sunita Williams added, “I have a real good feeling in my heart that the spacecraft will bring us home, no problem.”

Despite the lingering uncertainties, Williams and Wilmore are making the most of their extended stay on the ISS. They’ve been busy with tasks like changing out the pump on a machine that processes urine into drinking water and conducting science experiments, including gene sequencing in microgravity. They’ve also tested the Starliner as a ‘safe haven’ vehicle and evaluated its life support performance with four people aboard.

Before they can come home, engineering teams need to run more simulations of the thrusters and helium seals on the ground to understand the root causes of the technical issues. Initially, one helium leak was known before launch, but more emerged during the flight. While helium is non-combustible, it provides essential pressure to the propulsion system. Additionally, some of Starliner’s thrusters failed to kick in during its approach to the station, delaying docking.

Boeing executive Mark Nappi explained that the ‘working theory’ for the thruster malfunction was overheating due to excessive firing. Theories for the helium leaks range from debris entering the propulsion system to undersized seals installed by Boeing. Nasa and Boeing maintain that Starliner could fly home in an emergency, as the problems only affected certain orientation thrusters.

Nasa official Steve Stich assured that bringing Williams and Wilmore back on a SpaceX Crew Dragon isn’t yet being considered, despite the possibility. “The prime option today is to return Butch and Suni on Starliner,” he said, while acknowledging that a return flight on a SpaceX spaceship can’t be ruled out.

In 2014, Nasa awarded multibillion-dollar contracts to SpaceX and Boeing to develop crewed spaceships after the retirement of the Space Shuttle programme. SpaceX successfully carried out a crewed test in 2020 and has since flown dozens of people, leaving Boeing eager to prove its capabilities with the Starliner.