Club members have a blast launching model rockets thousands of feet into the Big Sky

GREAT FALLS, Montana USA -- Ten ... nine ... eight ...

About 15 people gather among the gently rolling hills between Twin Bridges and Melrose. At the sound of the countdown, they look up from their tinkering.

Seven ... six ... five ...

Their attention focuses on a launch pad some 50 feet away, connected by wires to the buzzing launch control box with a big red button.

Four ... three ... two ... one ...

The wind is fairly calm. The sky is mostly clear. If this one goes up the projected 7,000 feet, it will disappear for a while into the blue.

Wide open spaces make for safe and spectacular launches. Big Sky Rocketry has a 20,000-foot height clearance at the Twin Bridges launch site.

Launch.

Fwooosh!

The white rocket streams skyward, leaving a light condensation trail behind. The crowd murmurs in appreciation as it slips out of sight.

The rocket motor burns out, lighting a second fuse. About the time it reaches apogee, the highest point of the flight, a black powder explosion blows the tethered top off, releasing a parachute.

"There it is!"

Searching eyes pick out the gently drifting rocket above the backdrop of distant snowcapped peaks. The rocket eventually lands a couple of hills over, and its owner sets off to retrieve it.

When he gets back, he'll report how high it went. In the meantime, other club members continue preparing their rockets to meet the sky.

It's another successful launch for Big Sky Rocketry.

The club meets about twice a month when the weather is good, setting off model and high-powered rockets from two approved sites near Billings and Twin Bridges.

Dale Emery started the club in 1992. Like most of the adults in the club, he launched rockets as a kid and rediscovered the interest later in life.

"It is something the whole family can do together," said member Steve Shannon.

"It has the 'gee-whiz' appeal that a lot of us baby boomers grew up with during the 'Space Race' and it is just plain fun in a geeky sort of way for kids who have grown up with computers, video games and high-tech movies."

It's also educational.

"Kids learn physics, math, chemistry, and even electricity through rocketry," he added. "They also learn to work with their hands as well as their heads."

"How high can it go?" is one of the first questions in model rocketry.

The answer depends on a number of things, but two key factors are rocket weight and propulsion power.

The motors are basically tubes of solid propellant. Motor power is categorized alphabetically, with each letter having approximately twice the thrust of the last.

For instance, according to the list of National Association of Rocketry (NAR) approved motors, the little A motor has a total impulse of 2.5 newtons per second.

That would send a one-ounce rocket up about 200 feet, according to the Estes Rockets Web site.

B motors have twice the thrust, and go about twice as high, all other things being equal.

C motors, about the size of a roll of dimes, have a total impulse of 10 newtons per second. That would carry a one-ounce rocket about 1,000 feet.

You can find motors up to about D or E in hobby shops.

G motors are the most powerful of the hobby rocket motors. Starting with H, you're dealing with high power rocketry.

At these sizes you're no longer sending up a one-ounce rocket, but these puppies are still going to make some serious tracks.

The NAR list puts K motors at 1,300 to 2,500 newtons/second.

That worked out to about 6,700 feet for Andrew Horton's 9-foot-tall, 12-pound, modified Andromeda rocket at a Big Sky Rocketry launch in September.

As for speed, Horton expected the slim red craft to hit 0.8 Mach.

The largest NAR-approved motor is an N, with a whopping total impulse of 16,461 newtons/second.

Model rocketry began in the 1950s, when the Space Race was on and rocket scientists were the height of intellectual coolness.

The first amateur rockets weren't very safe, with metal frames and homemade propellants. Model rockets were created as a standardized alternative, with safer materials such as cardboard and balsa wood and professionally made single-use rocket motors.

Some serious hobbyists go beyond the kits to design their own. Simulation software helps ensure a stable flight, Emery said, by calculating elements such as the center of gravity and center of pressure to predict the outcome.

Whether from a kit or custom-made, all hobby rockets are subject to safety regulations.

These include selecting a proper launch site. The site size depends on how high the rocket is projected to fly, and it should be clear of buildings, power lines and other hazards.

Club members count down every flight, keep their distance from the launch pad, and make sure the sky is clear of aircraft.

Model rockets going up a few hundred feet pose little risk for aircraft, but higher-powered rockets can go a few thousand.

Big Sky Rocketry's record is 11,000 feet, Shannon said. The club has FAA clearance for 5,000 feet above ground level at its Billings site, and 20,000 at the Twin Bridges site.

"Amateur rockets have been flown to a high as 100,000 feet before," Shannon noted. "The motors it used were similar to the ones we launch, but larger."

Lloyd Magnuson leads a rocket club at Butte's East Middle School. His students' have reached 1,500 to 2,000 feet.

Last year, they tried a G motor in a rocket designed to carry a raw egg up to 850 feet using an F motor.

"It went to 1,500 feet," he said. "If we'd taken the egg out, probably would've pushed it to half a mile."

The smallest rockets — 16 ounces or less — are not subject to FAA regulations. Still, it's a good idea to clear it with the fire department before launching in town, said Charlie Butler, Great Falls fire inspector.

High-powered motors have the most stringent regulations. The president of Big Sky Rocketry has a Low Explosive User Permit to purchase them, while members who want to launch them need certification from one of the national rocket clubs.

Level one certification applies to H and I motors, level two to J, K and L, and level three for M, N, O and beyond.

In the early 1990s when Emery got back into rockets, he couldn't find anyone in Montana to certify him. He traveled to Salt Lake City for his level one certification, and Casper, Wyo., for his level two.

Now, with all three certifications under his belt, he helps certify others.

At Big Sky Rocketry's Sept. 23 launch, MSU-Bozeman student Cameron Chen was working on his Tripoli Rocketry Association certification.

Level one went off without a hitch, with an H motor powering the rocket loaded with parachute, altimeter and radio tracking device.

Level two didn't go quite as smoothly.

Armed with a J motor, the rocket was expected to hit 4,500 or 5,000 feet.

However, the delay was too short. Rather than letting momentum carry the rocket to its full height, the parachute was deployed early. The rocket hit only 3,813 feet, and it came down with a "zipper," a jagged tear in the tube.

Undaunted, the MSU team set out to fix it. Chen cut off six inches of the rocket body with a small hacksaw, while another student fed the new specs into the computer.

The rocket went up, up, up. Then the parachute should have launched, but didn't, so the rocket tumbled down, down, down, to meet the ground.

The students set out to find it. The pieces came back in a bag.

Crashes are all part of the fun, Horton said.

He's had his share of smashes and shredded rockets. He never did recover one that came down in a Canadian wheat field.

"When they work they're cool," Horton said, "and when they don't work they're really cool."

When it comes to unexpected performances, Magnuson has seen just about everything.

His students' rockets have come down in flames or without a chute, skipped across the ground or executed a loop-de-loop before continuing straight up.

Magnuson's club piqued Alex Clark and Jack Richards' interest in rocketry. The 15-year-olds launch with Big Sky Rocketry now, and both hope to go into aerospace design.

Last year, they traveled to Virginia for the Team America Rocket Contest.

Established in 2003 to celebrate a century of flight, the contest challenges school groups to send up a raw egg and return it unbroken. Last year they had to reach 800 feet and return within 45 seconds. This year's challenge is 850 feet. One year, it was two eggs as high as they could go within 90 seconds.

It was Butte's first year at nationals, where the eighth- and ninth-graders mostly competed against juniors and seniors.

"It's got a lot of science to it," Clark said.

Beyond the motor size and time, the students track temperature, barometric pressure and wind speed for an optimal flight.

Craftsmanship skills and patience are paramount for the first rockets of the year, Magnuson said. Later rockets involve computer simulations, construction and some experimental engineering.

"Building the rocket is the funnest part," said Jordan Richards, 13. "You get to design the rocket the way you want it to be."

Rockets are also a focus of MSU-Bozeman's Space Science and Engineering Lab.

"Our program is designed to be very much hands on," said professor David Klumpar, Ph.D.

When the college students build a rocket, it's not a matter of ordering parts and sticking them together. They actually engineer it from scratch, including mixing their own propellant and designing payloads.

Students in the program have also designed payloads to be sent into space on real rockets launched by the U.S. or Russia.

Getting started

"Rocketry is one of those hobbies that can be done on a child's budget or as much as a person wants to pay," Shannon said.

"A kid can go to a hobby store and buy a kit for about $5 to $10 and have a great time flying. An adult can build a kit for several hundred and outfit it with video cameras, telemetry equipment, and tracking equipment and spend a total of thousands of dollars.

"The nice thing is we enjoy the low priced flights as much as the high priced flights," he added.

A good place to get started is a hobby shop. Retailers of rocket supplies include Hobbyland and Michael's in Great Falls, Hobbytown USA in Helena, Depot Hobby in Shelby, and Jim's Junction in Billings.

The Internet is also a good source, especially for high power rocketry.

"Eventually, anybody who stays with the hobby ends up designing their own rocket to do what they want to learn about," Shannon said.

"People start with kits or buy the components and design their own. Some people even go to the lumberyard to get parts and build rockets from other such material. We have one member who is a master at building really nice looking rockets from the tube that carry plotter paper."

Estes Rockets dominates the entry-level market. Quest and Apogee also make rocket motors up to about size D. Aerotech is a big player through about size I, along with PML and Roadrunner. Animal Motor Works makes just about all the motors on the list larger than a K.

Big rockets, big motors and fancy payloads such as cameras are where the hobby starts to get spendy.

Remember that 16,461 newtons/second N motor, the largest on NAR list? Animal Motor Works sells them for $850 a pop.