A U.S. spaceship designed to one day fly astronauts to Mars blasted off Friday from Cape Canaveral Air Force Station in Florida for a 4½-hour unmanned trial run around Earth.

Riding atop a triple fountain of fire, the 24-story-tall Delta 4 Heavy rocket, the biggest in the U.S. fleet, lifted off at 7:05 a.m. and soared out over the Atlantic Ocean as it headed into orbit.

"The launch was just a blast . . . it was exciting," Mark Geyer, NASA Orion program manager, said in an interview on NASA Television.