Robert Behnken and Douglas Hurley, the NASA astronauts set to launch into orbit Saturday on a SpaceX rocket, are former military pilots, veterans of US space shuttle missions, and both married to fellow astronauts.

With their crew cuts, cool demeanor and short and precise sentences, they have all the traditional hallmarks of the men of NASA.

Smiling, competent, reliable: in short, "The Right Stuff" of the early days of space flight.

The pair known as Bob and Doug met in 2000 when they began training at the space agency. They have been best friends ever since, said Hurley, 53.

Both men attended military test pilot schools, a well-worn path to the astronaut corps.

Behnken, 49, a Missouri native, holds a doctorate in mechanical engineering from the California Institute of Technology.

He signed up for the military during his studies and trained at the elite Air Force Test Pilot School at Edwards Air Force Base in California.

A colonel, he has flown more than 25 different aircraft, including the F-22 fighter.

The New York-born Hurley also rose to the rank of colonel. Before joining NASA he was a fighter pilot and test pilot in the Marine Corps, a specialist in the F/A-18 Super Hornet.

Between 2008 and 2011, both men flew two missions, separately, on the space shuttle.

In 2015, NASA assigned them their next mission: the first crewed flight of the Crew Dragon, built by SpaceX and initially planned for 2017.

DREAM MISSION

"If you gave us one thing that we could have put on our list of dream jobs that we would have gotten to have some day, it would have been to be aboard a new spacecraft and conduct a test mission," Behnken said.

It was through the astronaut corps that Behnken and Hurley met their future wives, both of whom have space missions to their credit.

Behnken is married to Megan McArthur, and they have a six-year-old son, Theodore.

Doug is married to Karen Nyberg, and they too have a son, Jack, aged 10.

The bond of friendship that unites the two men is an obvious asset for such a risky mission, where either man might have to take control of the spacecraft that is set to autopilot by default.

Hurley is the more meticulous, even obsessive, of the two, said Behnken.

"If we have to get useless information, Doug is always the repository for that," joked Behnken in a video released by NASA.

Hurley himself admitted to being an expert in "obscure procedures."

As for Behnken, Hurley said his friend thinks of everything ahead of time. "He's already got it all figured out."

But he's no good at bluffing and "doesn't have a good poker face," added Hurley.

On Monday, the head of NASA texted the pair to ask one last time: are you sure you want to go ahead?

"They both came back and they said, 'we're go for launch,'" said Jim Bridenstine, the space agency's administrator. "So they're ready to go."

It's a moment they've been training for for the past five years.