Two astronauts due to make history have grown so close that one was best man at the other’s wedding.
Doug Hurley and Bob Behnken are making final checks ahead of becoming the first to fly a privately-funded crewed spaceship from American soil.
The duo were set to take off on Wednesday evening however the mission was aborted due to weather conditions at last minute — they are now set to leave at 3.22pm EDT (or 8.22pm UK time) on Saturday, May 30.
It will also be the first such manned US mission since American shuttle space-planes were retired in 2011.
The new spacecraft module, called Crew Dragon, is built by Elon Musk’s SpaceX, with Nasa paying the firm $3.14 billion ($2.55 billion) for design and development.
Hurley, 53, a retired Marine Corps colonel, and Behnken, 49, a US Air Force colonel, are two of Nasa’s most experienced astronauts.
They are due to blast off bound for the International Space Station orbiting 220 miles above earth at 8.33 pm GMT from with the module attached to a SpaceX Falcon 9 rocket.
The flight, called Demo-2, will test the capabilities of what has been described as an “astronaut taxi”.
The pair, who both have young sons, say they have become so close they are able to “predict” what the other’s next action will be and even attended each other’s weddings and Hurley was best man for Behnken.
The friends met each other and their future wives during gruelling Nasa training in 2000, with the four classmates all graduating to be selected for missions, and are now space veterans.
Mr Hurley’s wife, Karen Nyberg, has flown to space twice for a total of 180 days, in a US shuttle and also the Russian Soyuz, while Colonel Behnken’s wife, Megan McArthur, flew on the final mission servicing the Hubble Space Telescope in 2009.
Colonel Behnken told The Atlantic last year: ”That’s one of the things that is unique in our relationships: We have spouses that have the same job.
“If you even just look at our wedding planning, my wife and I were balancing space flights and a lot of stuff going on back here in Houston.
“Her flight got delayed a little bit and we found a window where we could get out to San Diego and have our wedding.
”Doug and Karen have to work their personal life around their spaceflights. And same thing for us. I know what he's going through.
“We both have sons in elementary school, we're balancing the same challenges.
“That lets us predict how to best support each other as we work through pulling off our next space flight."
Both astronauts - who have undergone regular Covid-19 testing - have flown in space twice before this mission.
Former fight pilot colonel Hurley was on the final flight of the space shuttle Atlantis in 2011 before the shuttle programme was discontinued, while Colonel Behnken has 37 hours of spacewalking experience.
Mr Behnken was a flight test engineer with the US Air Force before joining Nasa, and has spent just over 29 days in space, which includes 37 hours of spacewalking time.
If all goes according to schedule, blast-off is due from Florida’s Kennedy Space Centre at 4.33pm local time.
For the past two years, the pair have “essentially been living in California” working with SpaceX to get ready for liftoff.
The SpaceX enterprise fell almost four years behind schedule when original launch date was October 2016, after explosions destroyed a rocket and capsule.
For the journey, the astronauts will be dressed in white-and-grey SpaceX high-tech all-in-ones and delivered to the launchpad in a Tesla, the electric car firm owned by Musk.
Travelling at 17,000mph, they are due to reach the ISS about 19 hours later, where they will stay for between one and four months.
The focus of the mission is to testing how well the Crew Dragon flies in space, with controls including iPad-like touchscreens.
When they arrive at the ISS they will find seal inside the ISS docking hatch a small stars and stripes flag, just 8in by 12in, which was onboard the first space shuttle mission in 1981.
It was then left on the ISS in 2011 by the last shuttle missions, Atlantis, with an attached note: “Flown on STS-1 and STS-135. Only to be removed by a crew launched from KSC (Kennedy Space Centre)”.
