Stranded astronauts Suni Williams and Butch Wilmore finally head home

Their eight-day mission turned into an epic nine-month stay in space, and now Suni Williams and Butch Wilmore are on their way home.

The two astronauts who have been stranded in space for nine months are finally on their way back to earth.

Suni Williams and Butch Wilmore undocked from the International Space Station in a SpaceX Dragon capsule at around 3.05pm AEST on Tuesday.

Their homeward journey is expected to take about 17 hours with the capsule scheduled for splashdown off the coast of Florida, in the US, just before 8am on Wednesday.

The pair had originally planned for an eight-day mission when they left earth back in June last year, however engineers noted a helium leak and issues with the thrusters on the Boeing Starliner they were travelling on and so began their 286-day stay in space.

The SpaceX Dragon capsule left the International Space Station on schedule just after 3pm AEST. Picture: NASA

Inside the Dragon as the crew undocked. Picture: NASA

Williams and Wilmore are returning to earth with NASA astronaut Nick Hague and Russian cosmonaut Aleksandr Gorbunov, who arrived at the ISS together on a SpaceX Dragon capsule in September last year. Together, the four are known as Crew-9.

Crew-10, the four astronauts who are relieving Crew-9, arrived at the ISS on a SpaceX Falcon 9 rocket on Sunday, 16 March.

The last time Butch Wilmore and Suni Williams had their feet on the ground they were leaving Florida on a Boeing Starliner spacecraft in June last year. Picture: Joe Raedle/Getty Images

Plan for re-entry

NASA has released the schedule for the astronauts’ return home.

- 12.45pm Tuesday: Hatch closing on Crew-9. Hague confirmed the hatch was closed as Williams and Wilmore took their seats. They were about 20 minutes ahead of schedule.

- 3.05pm: Undocking from the ISS. The undocking process was fully automatic and required no intervention from the crew.

- 7.11am Wednesday: Deorbit begins. Rockets will be used to slow the re-entry of the capsule.

- 7.57am: Splashdown off the coast of Florida.

The SpaceX Falcon 9 rocket that carried Crew-10, who are relieving the stranded astronauts, left NASA's Kennedy Space Center on Friday. Picture: Aubrey Gemignani/NASA via Getty Images

NASA astronauts Anne McClain and Nichole Ayers, Japanese astronaut Takuya Onishi and Russian cosmonaut Kirill Peskov, known at Crew-10. Picture: Brandon Bell/Getty Images

Rehabilitation back on earth

Upon returning home, Williams and Wilmore will need to attend an extensive rebab program after such a long stay in space.

University of Melbourne’s space health topic co-ordinator Dr Rowena Christiansen, said one of the biggest risks faced by astronauts is weakened muscles and bones.

“An extended period in space can be quite challenging and quite taxing on your body,” she said.

“Because the muscles don’t have to work as hard to support the body, they can become weaker and get smaller.

“Alongside that, because your bones aren’t having to work against gravity, your bones lose minerals in microgravity, particularly calcium, and that can lead to a decrease in bone density.”

While in space, the astronauts exercised for 2.5 hours a day to help mitigate some of the negative impacts of zero gravity on their bodies.

Speaking before leaving the ISS, Williams described her time as varied.

“We’ve had opportunities to do all sorts of science, space walks - it’s a varied and pretty awesome opportunity to do something different every single day,” she said.