CAPE CANAVERAL, Fla.  On Wednesday, for first time since 1981, a rocket that was not a space shuttle took off from a launching pad at the Kennedy Space Center here.With a clearing in a partly cloudy sky, the Ares I-X rocket, a prototype of the National Aeronautics and Space Administration’s next-generation Ares I rocket, zipped off at 11:30 a.m., heading east over the Atlantic Ocean.

After rising through blue sky for two minutes, the first stage expended its fuel at an altitude of more than 25 miles, separated and parachuted into the ocean. After separation, the dummy second stage spun around before plunging into the ocean. The final Ares I rocket is to have a second-stage engine and a crew capsule to carry four astronauts into orbit to the International Space Station.

As tall as a 32-story building but with a first stage only 12 feet wide, the Ares I-X looked skinny and top-heavy. Yet it flew as envisioned.

For the NASA team working on the Constellation program to send astronauts to the Moon and beyond, the flight was a moment of smiles and joy, if not quite vindication. Critics have described the Ares I, which would be the first Constellation rocket to fly, as too expensive and technically flawed.