PROMONTORY, Box Elder County — Pelting rain and concern about distant lightning built suspense that a shuttle rocket booster might not be tested as planned Tuesday.

Then the sky cleared, the countdown resumed and the motor ignited with an incandescent flame.

Following a pause due to sound traveling slower than light, a throaty bellow slammed spectators stationed 1.3 miles away from the test frame. As the firing continued, the long, furious flame licked at the hillside. Billowing white and brown clouds tumbled and piled high into the sky. Hundreds of spectators were delighted.

Soon afterward, NASA announced that ATK Thiokol had successfully fired a solid rocket booster, "one of several annual tests . . . to qualify any proposed changes to the rocket motor and to guarantee that new materials meet safety requirements."

"These annual tests closely replicate a space shuttle launch," said a release from NASA's Marshall Space Flight Center in Huntsville, Ala.

Although the two hours of suspense about the test ended with a roar, the larger question remained unanswered — about the future of Thiokol's solid fuel booster production after the motors are no longer needed for the shuttle, due to retire in 2010.

But rumor, at least, has the future looking toward the moon and Mars.

Officials with both the company and NASA refused to confirm reports of a leaked NASA memo supposedly saying the northern Utah rocket builder will play a vital role in the next generation of rockets.

A rumor has been circulating that NASA wants Thiokol's boosters to power spacecraft that may carry Americans back to the moon and eventually to Mars. One Internet site, "The Houston Chronicles," speculates the northern Utah rocket maker "is currently the leading candidate for next generation launch systems."

Scott Horowitz, director of space transportation and exploration for Thiokol — a former astronaut who has orbited in four shuttle flights — said the company has been working for a couple of years on its designs for the next generation of space vehicles. A crew-launch vehicle and a heavy-lift cargo vehicle both would use Thiokol motors, he said in an interview shortly before the test.

For the crew-launch vehicle, he said, "The first stage is the same as the motor that we're going to see out here tested today, a four-segment, solid-rocket motor."

The heavy-lift vehicle would be like the shuttle lifters but with a cargo shell instead of the shuttle. The twin boosters would be bigger — five segments instead of the four used with the shuttle.

"Everything that we know is that NASA is completing . . . what they're calling their 60-day study. They have to understand the architecture of how to go back to the moon and Mars. And that architecture should define the launch vehicles to go carry that out," Horowitz said.