After SpaceX's arrival, the spacecraft will have completed its final key test to prove it can transport astronauts to and from space.

This photo shows, from left, front, astronauts Bob Behnken and Doug Hurley during an interview on the International Space Station on Saturday, Aug. 1, 2020.
This photo shows, from left, front, astronauts Bob Behnken and Doug Hurley during an interview on the International Space Station on Saturday, Aug. 1, 2020. (NASA via AP)

The first astronauts launched by Elon Musk’s SpaceX company have departed the International Space Station for the final and most important part of their test flight: returning to Earth with a rare splashdown.

NASA’s Doug Hurley and Bob Behnken bid farewell to the three men left behind as their SpaceX Dragon capsule undocked and headed toward a Sunday afternoon descent by parachute into the Gulf of Mexico.

"It's been a great two months, and we appreciate all you've done as a crew to help us prove out Dragon on its maiden flight," Hurley told the remaining US station crew member Chris Cassidy, as Crew Dragon autonomously eased away from its docking port to begin the 21-hour journey home.

Despite Tropical Storm Isaias’ surge toward Florida’s Atlantic shore, NASA said the weather looked favourable off the coast of Pensacola on the extreme opposite side of the state.

First splashdown after almost 50 years

It will be the first splashdown for astronauts in 45 years. The last time was following the joint US-Soviet mission in 1975 known as Apollo-Soyuz.

The astronauts' homecoming will cap a two-month mission that ended a prolonged launch drought in the US, which has relied on Russian rockets to ferry astronauts to the space station since the end of the shuttle era.

In launching Hurley and Behnken from NASA's Kennedy Space Center on May 30, SpaceX became the first private company to send people into orbit. Now SpaceX is on the verge of becoming the first company to bring people back from orbit.

“The hardest part was getting us launched, but the most important is bringing us home,” Behnken said several hours before strapping into the Dragon.

A successful splashdown, Behnken said, will bring US-crew launching capability “full circle.”

Behnken and Hurley will have a few hours for sleep during their journey home in the capsule, which will gradually decrease its orbital altitude through a series of automated thruster firings.

"They've got plenty of food and water aboard the spacecraft," SpaceX engineer Siva Bharadvaj said during a livestream of the undocking.

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Meaningful flag

At a farewell ceremony earlier in the day, space station commander Chris Cassidy, who will remain on board with two Russians until October, presented Hurley with the small US flag left behind by the previous astronauts to launch to the space station from US soil.

Hurley was the pilot of that final shuttle mission in July 2011.

The flag – which also flew on the first shuttle flight in 1981 – became a prize for the company that launched astronauts first.

SpaceX easily beat Boeing, which isn't expected to launch its first crew until next year and will land in the US Southwest. The flag has one more flight after this one: to the moon on NASA’s Artemis program in the next few years.

“We’re a little sad to see them go," Cassidy said, “but very excited for what it means to our international space program to add this capability” of commercial crew capsules.

The next SpaceX crew flight is targeted for the end of September.

Hurley and Behnken also are bringing back a sparkly blue and purple dinosaur named Tremor. Their young sons chose the toy to accompany their fathers on the historic mission.

Source: TRTWorld and agencies