DOTHAN, Alabama USA (AP) — Rocket science is a lot of trial and error. That's what Samson native Chris Crews has learned from his work in trying to design and build a model rocket capable of flying up to 850 feet in 45 seconds and parachuting back to earth without damaging its payload, an egg.

Crews has about two weeks left to perfect his rocket for the Team American Rocketry Challenge in The Plains, Virginia. Crews is one of only two students from Alabama to qualify for the competition.

It's a balancing act that requires design and construction skills and the use of several mathematical formulas. For instance, when building a rocket it's vital to ensure that the center of gravity is above the center of pressure or else the rocket will become unstable and crash on liftoff.

Even if the design's right, there's a number of construction issues that can come into play. Crews model rocket recently had a mishap when an ignition problem caused some of the engines to fail to ignite, causing the rocket to fly in loops before coming to rest.

"It didn't hurt the rocket or break the egg though," Crews said.

Crews got interested in rocketry about two years ago after seeing members of the Southeast Alabama Rocketry Society flying model rockets near his home in Samson. Crews started out flying prebuilt rockets purchased at Wal-Mart, but now builds his own from scratch.

Model rocket components can come from just about anywhere. Crews uses fiberglass for fins on the rocket he's taking to competition and parts from a fishing pole have been recycled into launch lugs, which hold the rocket on its launch rail.

A more high tech component of the model rocket is a sensor it carries that records how high the rocket climbs. Technological wizardry also comes into play during the design process. Crews uses a program called RocSim to help do some of the equations necessary to design the rocket.

Crews hobby may lead to a career. The Samson High School student intends to pursue a degree in engineering by attending Enterprise-Ozark Community College before transferring to Auburn.

Copyright © 2007, The Associated Press.