CAPE CANAVERAL, Fla. – The much awaited dress rehearsal for SpaceX's powerful Falcon Heavy rocket has moved, yet again.

The last known window for the rocket to fire all of its 27 Merlin engines on Kennedy Space Center pad 39A was Friday, but after a United Launch Alliance liftoff scheduled for Thursday was moved to Friday, SpaceX is now targeting Saturday morning.

United Launch Alliance is set to launch a U.S. Air Force missile tracking satellite from Space Launch Complex 41 on Friday night, which means the Space Coast range will be occupied. If Atlas V launches without another delay, that clears the way for the Falcon Heavy testing to continue.

The ULA launch is a high-priority mission for the U.S. Air Force and therefor gets priority over the SpaceX test.

The SpaceX Falcon Heavy test fire could happen Saturday after 2:45 p.m. SpaceX has until 9:30 p.m. to fire up all 27 engines. The rocket went vertical on the launchpad Thursday evening.

It’s possible the attempt will continue to be rescheduled as SpaceX continues to test its new rocket. SpaceX CEO Elon Musk said in December the company was targeting January for Heavy's maiden voyage.

“Testing of a brand new rocket and brand new ground equipment. This was always going to take some time to get through,” NASASpaceflight.com editor Chris Gebhardt said. “They want to make absolutely certain everything is perfect before lighting up 27 engines at the same time and running them for 12 seconds."

Follow updates on Falcon Heavy's maiden voyage at ClickOrlando.com/space.