Nasa is set to test launch the Orion space capsule this morning, set be the longest flight of a spacecraft made for humans since the 1970s and an important step on the way to a manned mission to Mars.
Orion will launch on a Delta IV rocket, the largest rocket in America's current inventory.
The craft is set to launch at 7:05 a.m. EST (12:05 GMT). The latest update from Nasa said there were no technical problems reported so far and that the weather forecast called for a 70 per cent chance of acceptable conditions for the launch to take place on time.
It will then fly 3,600 miles into space before heading back, about four hours after launch, crashing into the Pacific Ocean.
You can follow the test launch below with Nasa's live stream:
The rocket will be fitted with 1,200 sensors that will test whether humans would be able to survive the flight.