Nasa SpaceX launch set to usher in new era for human spaceflight
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 the low-Earth orbit is entirely commercialized, where Nasa is one customer among many customers, and where we have many providers competing on cost, on innovation and safety."
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 20:33 GMT.
Their ascent to orbit should take a little under nine minutes. A series of further maneuvers will see the men's capsule dock with the ISS on Thursday at 15:29 GMT.
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.