SANTA CRUZ, California USA — Clayton Gross grins widely as he pushes play on his VCR. Appearing on the screen, in the middle of what looks like nowhere, is a long and sleek black rocket, about 5 feet high. In the background, an announcer's voice begins a countdown. "10 ... 9 ... 8 .." After "1", an ignition is heard, a blue flame shoots out the bottom of the rocket and it quickly becomes a black speck in the sky about 4,100 feet overhead.

"It took us a long time to find where that one landed," said Gross, a 15-year-old freshman at Scotts Valley High School. "There are a couple different kinds of motors; the White Lightning and the Blue Thunder. The Blue Thunder has the most thrust, and that's what we used for that rocket. It landed about a mile away from where we launched it"

Gross and his father, John, have been building model rockets together for about five years. They started out building the small ones that you can launch in a city park [provided the police happen to be looking the other way]. Soon they graduated to larger rockets with more powerful motors. These days, they're launching rockets that require a Level 2 certification from the National Association of Rocketry [NAR], which the elder Gross acquired last year.

"We go out to Snow Ranch, outside of Stockton, about once a month for a launching held by the Livermore Unit of the National Association of Rocketry [LUNAR]," said John Gross. "There are usually about 300 people there, and it's a real blast," he said without a hint of irony.

The black rocket Clayton watched on his VCR is named after his favorite band Nirvana; the band's logo adorns the entire length of the black projectile. But that isn't the coolest thing about it.

"We did some personalization on this one," Clayton says as he opens up the rocket to reveal a circuit board. "We installed this to measure altitude and air pressure. It tells the parachute when to deploy and also gives us information about the flight"

Standing in front of the Grosses' fireplace are about 10 rockets of all shapes and sizes, including the first one father and son built together. It measures less than a foot tall and is dwarfed next to the Nirvana rocket. Others stand as tall as the Nirvana rocket, but are super slim. One custom-built rocket has a clear body that they insert glow sticks and small strobes into for colorful night launches.

In addition to the Snow Ranch launch, the Grosses also attend launches in the Black Rock Desert in Nevada, where some rockets are launched up to 30,000 feet into the air. 

The altitude a rocket reaches is determined more by the power of the motor installed rather than the shape of the rocket.

The motors are made of ammonium perchlorate — which is actual rocket fuel, but obviously in much smaller amounts — housed in a metal casing that can be reused.

There are different sizes of engines; "A" through "G" are the smallest and require no certification to use. "H" through "I" require Level 2 certification and anything "M" and above requires the highest Level 3 certification. Certification tests happen at NAR-sponsored launches, which are run according to a set of rules and guidelines for obvious safety reasons.

"The rules they set are very strict, but they don't get in the way of the fun of it all," said John Gross, who has an engineering background but only began building rockets with his son. "In all the launches we've been to, there's never been an accident"

One of the most useful tools the Grosses use when designing and building their rockets is a computer program. They enter the dimensions of the rocket into the computer, including length, girth and fin size and placement, then a computer simulation shows the flight path the rocket will take. If there's a flaw in the design, the computer shows the rocket spiraling off in the wrong direction and will identify where the problem lies.

There are currently no local rocketry groups in Santa Cruz, which is why the Grosses travel to launches. They're hoping to find some kindred spirits to launch with locally. They're also on the lookout for a kind soul who owns an expanse of property so they can launch their larger rockets without having to travel to Stockton or the Black Rock Desert.

For more information on rocketry, visit the NAR Web site at http://www.nar.org, or the LUNAR Web site at http://www.lunar.org.