NASA hopes to launch an Orion crew capsule into space for the first time before the end of this year — two or three months later than previously planned.

Once targeted for September or October, the mission called Exploration Flight Test-1, or EFT-1, is now shooting for an early December launch atop a Delta IV Heavy rocket from Cape Canaveral Air Force Station.

Kennedy Space Center Director Bob Cabana said Monday that contractor teams areworking seven days a week in the center’s Operations and Checkout facility to get the test capsule ready for the uncrewed first flight.

Orion will circle Earth twice, climbing 3,600 miles above the surface to set up a fiery plunge through the atmosphere at speeds close to those Apollo crews experienced when returning from the moon. Splashdown will follow in the Pacific.

“I assure you that Orion is going to be ready to go on time,” said Cabana. “And as soon as we get our opportunity, we’re going to be launching that vehicle on its first flight test, and that is pretty darn amazing.”

NASA could not immediately confirm the mission’s cost.

NASA officials said that the slip allowed an Air Force satellite launch to move ahead of the Orion launch. It was not clear if Orion and the rocket otherwise would have been ready on time.

What does not change are plans for a December 2017 launch of another Orion on the maiden flight of the agency’s giant Space Launch System rocket, or SLS, said Robert Lightfoot, associate administrator at NASA headquarters.