Test pilot Michael Melvill flew a stubby civilian-built rocket plane 337,500 feet into suborbital space Wednesday, overcoming a series of spectacular unplanned rolls in a bid to win the $10 million Ansari X Prize.

A jubilant Melvill glided SpaceShipOne gently to a stop on a remote airstrip in the Mojave Desert, dismissing the journey's dramatic climax as a "a victory roll." Engineers said that the spacecraft has rolled on every flight but that they are investigating the cause.

"You just cannot describe what a feeling this is," Melvill said, standing on the tarmac. "I just loved every second of it. Maybe I'm crazy."

Melvill easily reached the 100-kilometer (328,084 feet) altitude defined as "space" and put SpaceShipOne on track to fly again by Oct. 13 to claim the X Prize. Designer Burt Rutan has suggested the spacecraft may fly as early as Monday but said the team will make a final decision today.

"The ship has no squawks -- there is nothing to fix," Rutan said at a news conference after the flight. "The motor is in beautiful shape, and we are analyzing whether there are any safety issues."

The X Prize competition, which has attracted 26 teams worldwide, requires that the winning craft -- made by a civilian entrepreneur with no government financing -- carry three 198-pound people, or a pilot and equivalent ballast, into suborbital space, then repeat the feat within two weeks.

X Prize Foundation Executive Director Gregg Maryniak, a competition judge, said Melvill's flight topped out at 337,500 feet, but the figure would not be final until confirmation comes from engineers at Edwards Air Force Base. He predicted the Edwards result would not differ by much.

The competition is patterned after the $25,000 Orteig Prize won by Charles Lindbergh in 1927 for the first nonstop flight from New York to Paris, and is designed to stimulate interest in space tourism. Earlier this week, British entrepreneur Richard Branson's Virgin Group announced that it was licensing the SpaceShipOne technology in hopes of beginning suborbital flights for tourists by 2007.

Virgin is a sponsor of SpaceShipOne's X Prize attempt, and the rocket plane wore the company's "Virgin Galactic" logo on its tail Wednesday, one of myriad endorsements and publicity initiatives that were visible -- or audible on loudspeakers -- at the Mojave Civilian Aerospace Test Center.

The gaggle of high-rolling new sponsors contrasted sharply with SpaceShipOne's premiere space flight on June 21, which was a relatively austere affair despite generous financing by Microsoft co-founder Paul Allen, who said he has spent more than $20 million on the project. That flight put Melvill -- alone with no ballast -- into suborbital space, making him the first civilian to earn astronaut's wings flying for a civilian company.

Wednesday's flight had endorsements from celebrities, praise from NASA Administrator Sean O'Keefe for the Rutan team's "spirit of innovation" and a webcast that began in the chill darkness of the high desert at 6 a.m. Pacific time (9 a.m. Eastern).

By that time, thousands of people had begun to gather in roped-off areas along the tarmac to witness the flight. Food stands sold pizza and drinks, and a souvenir stall offered inflatable SpaceShipOnes for $10 and "silk blend peach piquet shirts" bearing the X Prize logo for $100.

"I think it's fabulous," said Heather Perry, 36, who owns a greeting card business in Torrance, Calif., near Los Angeles, and drove in for the launch with her husband, Heath. "I love all this stuff; I just wish I had the courage to do it. I have a fear of flying."

Melvill, 63, lifted off at 7:11 a.m. Pacific, slung below White Knight, the wispy aircraft that carried him to an altitude 50,000 feet before cutting SpaceShipOne loose. An egg-yolk morning sun bathed the airfield, quieting the wind.

Melvill had aboard several hundred pounds of ballast, mostly mementos and memorabilia, including seedlings from the desert and Terrence, a teddy bear that flew with U2 spy flight pilots.

Rutan sent along his college slide rule and the ashes of his mother, who died in 2000. Employees who worked on the project sent tools and other personal objects, in some cases signing releases promising not to sell the items.

At 8:10 a.m. White Knight released SpaceShipOne. Its rocket boosters ignited a few seconds later, fueled by a combination of nitrous oxide (dentists' laughing gas) and hydroxy-terminated polybutadiene (a clear rubber), to accelerate to a speed of Mach 3.2, or 2,400 mph.

The plane ascended like a shot, spewing a contrail in the clear, blue sky. Fifty seconds into the rocket's burn, however, it started to roll like a gigantic howitzer shell, eventually making more than 20 rotations as Melvill shut the engines down and coasted into space. "This does not appear to be a scripted maneuver," the webcast commentator announced.

But when Melvill landed at 8:34 a.m. he appeared anything but chastened. "The rocket ran like a dream," he yelled to reporters from the tarmac. "Did I plan the roll? I'd like to say I did, but I didn't. Probably I stepped on something too quickly."

Rutan, however, discounted both pilot error and wind shear, blamed for badly joggling SpaceShipOne during the June flight. Instead, he suggested that the plane had an intrinsic problem with "dihedral effect," in which air buffeting the spacecraft at an angle causes it to roll.

This occurs to some degree in all aircraft, but in SpaceShipOne it happened during every flight and "much too much," Rutan said. "We wrestle with it all the time," he added, but it does not appear to harm either the aircraft or the pilot.

"I didn't have any discomfort," said Melvill, adding that he had many hours of practice coping with the roll during flight simulations. "It was kind of cool. It was a spectacular view watching the world go around."

Pilot Mike Melvill celebrates on top of SpaceShipOne after landing. The craft reached an altitude of about 337,500 feet, into suborbital space.