"We are go for launch, which is absolutely outstanding," Robert Cabana, NASA associate administrator, told reporters at a press conference Monday night. "This day has been a long time coming."

If the Space Launch System (SLS) rocket successfully launches, shoots its Orion spaceship around the moon, and the spaceship survives the fiery plummet back through Earth's atmosphere, NASA could be on track to put boots on the lunar surface in 2025 — the first human moon landing since 1972. Eventually, NASA plans to build a permanent base on the moon and mine resources there, before sending astronauts on to Mars.

The rocket is sitting on Launchpad 39B at Kennedy Space Center, after being rolled out last week. Space agency officials say liftoff is scheduled for Monday, August 29, during a two-hour window that opens at 8:33 a.m. ET.