Nasa SpaceX launch set to usher in new era for human spaceflight
Two US astronauts are about to go to orbit in a commercially developed rocket and capsule system.
American space agency (Nasa) astronauts Doug Hurley and Bob Behnken will create a piece of history on Wednesday when they launch from the Florida coast.
The pair's trip to the International Space Station (ISS) will be made in a rocket and capsule system provided by a private company, SpaceX.
Nasa has traditionally always owned and operated its space vehicles.
But that is a capability it gave up in 2011 when it retired the last of the space shuttles.
The agency now wants to contract out all future crew transportation to low-Earth orbit to the commercial sector.
And assuming Wednesday's flight goes well, this new way of working will be implemented in full.
"We're starting a new era in space; it's an era when space is going to be available to more people than ever before," explained Nasa Administrator Jim Bridenstine.
"We envision a future where low-Earth orbit is entirely commercialised, where Nasa is one customer among many customers, and where we have many providers competing on cost, on innovation and safety."
- Astronauts complete rehearsal for historic launch
- Who are Doug Hurley and Bob Behnken?
- Why is this particular mission so important?
SpaceX regularly puts satellites into orbit but this is the first time it will have taken people above the atmosphere.
Hurley's and Behnken's lift-off from the Kennedy Space Center is scheduled for 16:33 local time (20:33 GMT / 21:33).
Their ascent to orbit should take a little under nine minutes. A series of further manoeuvres will see the men's capsule dock with the ISS on Thursday at 15:29 GMT (16:29 BST).
It's unclear at the moment how long they'll spend on the orbiting outpost before coming home, but it's likely to be just short of four months.
Anyone who remembers how the shuttles were launched and tunes in to see the SpaceX lift-off will witness a very different type of event. All the details have had a thoroughly modern make-over.
The astronauts now wear sleek, white pressure suits; they make their way to the pad in one of SpaceX CEO Elon Musk's electric cars; and they sit in their capsule behind a touchscreen display.
But if it looks flash on the surface, Nasa has insisted through a nine-year development programme that all the engineering detail underneath is second to none.
"The end certification process is the same as it's always been," observed Garret Reisman, a former Nasa astronaut and consultant to SpaceX.
"Nasa has been extremely rigorous in making sure that all the requirements are met, all the safety levels are where they should be, and all the I's are dotted and the T's are crossed.
"It's because of this process, as long and as arduous as it has been, I'm confident my friends Bob and Doug are going to be okay," he told BBC News.
Hurley and Behnken were chosen for this mission in part because of their experience. Both have flown to space twice before. Hurley was actually the pilot on that very last shuttle outing.
The run-up to the launch has had to contend with the coronavirus crisis, of course. This hasn't made a massive difference to the astronauts' preparations.
They would ordinarily go into quarantine prior to a mission anyway, to ensure they carry no illnesses up to the space station.
Nasa has, though, made a special effort to limit the number of people allowed to come into contact with them. And everyone, including Hurley and Behnken, have been subjected to regular Covid-19 testing.
"It's been relatively normal," Hurley said. "After all these years, we're kinda just used to all the poking and prodding and blood draws that come with all the other things that go with flying into space."
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