MOJAVE - Take a few shouted choruses of the traditional launch countdown. Add the hiss of a model rocket engine, a streak of white smoke and a small, dark object in a clear desert sky. Throw in the enthusiasm of more than 400 elementary school students, complete with team shirts, banners and cheers, and you have the Intermediate Space Challenge. The challenge, conducted Friday morning at the Mojave Air and Space Port, pits classroom teams of fourth-, fifth- and sixth-graders from Mojave and California City schools in a competition to build a high-flying model rocket as well as to create...