Sunita Williams becomes the second astronaut to spend the longest time in space – who holds the record?

Williams, along with astronaut Butch Wilmore, is returning to Earth after spending more than nine months at the ISS.

NASA astronaut Sunita Williams has become the second astronaut to spend the longest cumulative time in space. With a total of 608 days in orbit, Williams now surpasses many spaceflight veterans, but she still falls short of Peggy Whitson, who holds the NASA record at 675 days.

Williams’ latest mission, which was meant to be short, turned into an unexpectedly extended stay aboard the International Space Station (ISS) due to a spacecraft malfunction. Her return to Earth, scheduled for today, marks the end of yet another chapter in her extraordinary spaceflight career.

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Sunita Williams and fellow astronaut Butch Wilmore originally launched on June 5, 2024, aboard Boeing’s Starliner for a brief mission to the ISS. However, technical issues, including thruster malfunctions and helium leaks, made it unsafe for Starliner to bring them back to Earth.

By September 2024, NASA decided to return the Starliner spacecraft to Earth unmanned, leaving Williams and Wilmore stranded on the ISS until an alternative return plan could be arranged. They continued working on scientific experiments and station maintenance for an unexpectedly extended nine-month mission until a return vehicle—SpaceX’s Crew Dragon—was scheduled to bring them home.

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Their return journey officially began today with the undocking of the Crew Dragon spacecraft, and NASA will provide live coverage of their splashdown later tonight.

While Williams and Wilmore are in good health, returning to Earth after a long-duration spaceflight presents unique challenges. Astronauts experience muscle atrophy, bone density loss, and balance issues due to prolonged exposure to microgravity. As a result, they will be carried out on stretchers upon landing to ensure a safe transition back to Earth’s gravity.

Williams, however, has been preparing for this moment. “Been working out for the past nine months. We feel strong and ready to tackle Earth's gravity,” she wrote in an email to her NASA team before departing the ISS.

Who Spent the Most Time in Space?

While Williams now holds the second-highest cumulative time in space among NASA astronauts, she is still behind Peggy Whitson, whose record of 675 days remains unmatched. Other notable astronauts in this ranking include:

• Peggy Whitson – 675 days
• Sunita Williams – 608 days
• Jeff Williams – 534 days
• Mark Vande Hei – 523 days
• Scott Kelly – 520 days