NASA’s Ares 1-X rocket roared into the sky over the Kennedy Space Center today in the first test of what may in due course substitute the nation’s aging fleet of space shuttles.

“Three, two one, ignition — and liftoff of Ares 1-X,” George Diller, NASA’s launch commentator, said as the rocket left the pad.

The rocket took off from launch pad 39B at 11:30 a.m. ET, after waiting more than three hours for Florida’s famously changeable weather to clear. Skies today at the launch site were partly cloudy, but controllers worried that static electricity could build up on the rocket as it rose above the Atlantic ocean.

The flight was brief. The rocket’s first stage burned for two minutes as planned, lifting the Ares to an altitude of a bit less than 30 miles. The second stage, and the Orion spacecraft mounted on top, were mockups for this first test.

The two stages separated as scheduled, but long-range cameras showed the unpowered second stage turning sharply and beginning to tumble a moment later. NASA managers said they were not sure if there was an actual problem. On future flights the upper stage will be set to fire as it pulls away from its booster.

Maximum speed today was about 4.7 times the speed of sound. On operational flights to orbit, it will need to reach 25 times the speed of sound. For this test flight, the booster carried more than 700 electronic sensors to measure pressure, strain, acceleration and over effects, and NASA said it would take months to digest all the data from them.

The first stage is designed to be reused, with parachutes to lower it into the water after it uses up its fuel. NASA has two ships to tow it back to the Kennedy Space Center.

“Think about we just did,” said launch director Ed Mango to his team after the Ares had finished its flight. “Our first flight test, and all we had to wait for was weather. That’s frickin’ fantastic.”

Former astronaut Robert Cabana, who now heads the Kennedy Space Center, then took the microphone. “That was just unbelievable, that was fantastic,” he said. “It brought tears to my eyes.”

Veteran flight director Gerald Griffin was there to see the rocket go. “I think it is historical because it is the first new step we have taken in 30 years,” he said in an interview with ABC News. “We are now off on a new adventure.”

Launch had originally been scheduled for 8 a.m. ET, but that time came and went as mission managers waited for the weather risk to go down. They finally launched with half an hour to spare.

There had been several lightning strikes overnight near the launch pad, some less than 700 yards from the rocket itself. Giant lightning rods have been added to pad 39B for the Ares project, and they towered over the booster.

The launch window for Tuesday and today ran from 8 a.m. to noon, so that there would be several hours of daylight after the test was over.

The first stage of the Ares rocket is an updated version of the solid rocket boosters strapped to each side of a space shuttle’s orange fuel tank. The boosters have been used since 1981. One failed, tragically, causing the Challenger explosion in 1986, but they have been heavily modified since then.

The Ares was meant to be simpler, cheaper and more reliable than the shuttles. If it ever carries astronauts, they will be in a cone-shaped capsule on top of the rocket — considered safer than the shuttles, which are attached to the side of their external tanks and have often been hit by debris falling from the tanks during launch.

The 2003 Columbia tragedy was believed caused by foam from the fuel tank, coming off and damaging the shuttle’s wing.