A towering orange-and-white NASA rocket blasted off from Florida on Wednesday evening, lifting four astronauts toward space and transporting spectators’ imaginations to a future in which Americans may again set foot on the moon.

As they did during the heyday of the Apollo program, which first put men on the lunar surface, spectators squeezed onto the beaches along Central Florida’s Space Coast. The crowds cheered when the powerful rocket launched into the clear sky at 6:35 p.m. Eastern time. It traveled eastward, over the Atlantic Ocean, on a journey that will take astronauts around the moon but not land there.

“We have a beautiful moonrise and we’re headed right at it,” said Reid Wiseman, the NASA astronaut who is the commander of the mission, as the crew headed into space.

Tens of thousands of excited spectators exclaimed and hugged along Cocoa Beach and surrounding communities as the rocket shot into the sky on a column of fire and a long white vapor trail.

“The contrast against the blue sky was absolutely remarkable,” said Anthony Rodriguez, 35, of Orlando. “It’s just an unforgettable sight.”

The flight aboard a spacecraft named Integrity is taking Mr. Wiseman, Victor Glover, Christina Koch and Jeremy Hansen on what is expected to be a round trip of more than 695,000 miles to clear a path for more exploration, a new lunar landing, eventually a sustained human presence on the moon, and journeys farther out into the solar system.