Hundreds of onlookers gasped when the brightest flare this side of the sun shot from a booster motor anchored to the ground across a small valley. Several seconds later, a continuous roar enveloped the spectators. It was the first nighttime test by ATK Launch Systems of one of its immense solid rocket boosters since 1992. NASA officials, contractors and other experts stood amazed Thursday, as the gigantic flame stretched along the ground, brilliant white in the centre, orange-red above. A nearby mountainside, dark seconds before, was bathed in bright light, every boulder and ridge etched in white with black shadows.