The American Boeing company is about to run another demonstration mission of its new astronaut capsule.
The CST-100 Starliner is set to launch from Florida to showcase how it can ferry crews to and from the International Space Station (ISS).
It will be the second test flight, and conducted with no people aboard.
The previous demonstration, in 2019, encountered software problems that very nearly resulted in the loss of the capsule.
The Starliner will ride to orbit on an Atlas-5 rocket from the Cape Canaveral Space Force Station in Florida.
Lift-off is timed for 13:20 local time (17:20 GMT; 18:20 BST).
Controllers had been targeting Friday last week for the launch, but a mishap involving a newly installed Russian module on the ISS forced a four-day delay.
Assuming there’s no further hold-up, the Starliner will aim to dock with the station shortly before 17:40 GMT on Wednesday.
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- It’s just over 10 years since Boeing first presented its design for the CST-100 Starliner at the Farnborough Air Show in the UK.It was a response to the call for commercial companies to take over the responsibility for low-Earth orbit crew transportation, post the soon-to-retire space shuttles.The US space agency (Nasa) gave technical and financial support to both Boeing and the SpaceX company, to help them develop new capsules. The idea was that the vehicles would then be engaged on a commercial basis whenever Nasa needed astronauts sent up to the ISS.But while SpaceX is now two crewed operational flights into this privatised era, Boeing has yet to run a single crewed mission in a Starliner. And that’s because Boeing’s first unpiloted “Orbital Flight Test” in December 2019 went seriously awry.The problems started with a clock error on the capsule just after launch that made the vehicle think it was in a different flight phase than was really the case.