For first time since 1981, the rocket that took off from a launching pad here at the Kennedy Space Center on Wednesday was not a space shuttle. With a clearing in a partly cloudy sky, the Ares I-X -- a prototype of the National Aeronautics and Space Administration's next-generation Ares I rocket -- zipped off at 11:30 a.m., heading eastward 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. But the machine flew as envisioned. For 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 criticized the Ares I, which would be the first Constellation rocket to fly, as too expensive and technically flawed. 'Vindication really does not describe it well,' Jeffrey Hanley, the Constellation program manager, said, smiling, at a news conference after the flight. 'It's a sense of validation that the course we have laid out is executable.' The flight should also sweep aside any doubts that the design is workable, Hanley said. A blue-ribbon panel reviewing NASA's human spaceflight program said Ares I faces no insurmountable problems but wondered if NASA might better spend its effort on a heavy-lift rocket and turn the business of carrying astronauts to private companies. With the success of the Ares I-X, proponents of Constellation may argue more passionately that maintaining the current path is a better choice. 'All the naysayers, that was just one of the most beautiful rocket launches I've ever seen,' said Robert Cabana, director of the Kennedy Space Center. Liftoff, which had been scheduled for 8 a.m., was delayed as engineers checked electronic systems after lightning struck within a half-mile of the launching pad last night. Once ready, the mission managers waited on the weather. For spectators on the ground, the weather seemed not bad at all, with no signs of rain and a sky of broken clouds. But because the Ares I-X is a new design, the weather criteria were more stringent than for a shuttle launching. The worry was that if the rocket flew through a cloud, the friction of the water droplets could have created static charge and disrupted communication. At 11:20 a.m., a break in the clouds big enough for the rocket opened up, and 10 minutes later, the rocket's engine -- essentially a space shuttle solid rocket booster -- ignited with a window-rattling roar. By design, the rocket tilted away from the launch tower, then headed skyward. The success came a day after launching efforts were thwarted by cloudy skies. The Ares I-X carried more than 700 sensors to measure the stresses and strains on the spacecraft. The data from the $445 million flight will allow engineers to refine their computer models and designs. The first flight of the Ares I carrying astronauts is scheduled for March 2015. 