Under new provisions set to go into effect May 24 under the Homeland Security Act, the Bureau of Alcohol, Tobacco, Firearms and Explosives would place further restrictions on the fuel that powers the rockets.
"You can't even estimate the devastating effect this is going to have on the hobby," said Bruce Kelly, the publisher of High Power Rocketry, a hobbyist's magazine.
Hobbyists have won the support of Sen. Mike Enzi, R-Wyo., who is drafting legislation to free rocketeers from the rules. His spokesman dismissed government claims that the regulations would better track explosives while not being "overly burdensome" to buyers.
Sport rocketry attracts thousands of hobbyists across the country. The rockets can stand taller than an adult, soar miles into the sky and are designed to land intact nearby.
The new rules will require buyers of the rocket fuel, APCP, to submit their fingerprints and photographs to ATF. The bureau will check applicants' backgrounds to see if they are among those banned from possessing explosives - felons, for example.
ATF also will inspect the areas where permit holders store explosives at least once every three years. It will not examine records those people keep, ATF specialist Chad Yoder said.
Currently, permits are required only if a person is receiving the fuel from across state lines.
Enzi says the rules will discourage people from taking up the hobby. The senator and some hobbyists maintain that the regulations also will threaten some educational programs.
The ATF says the most commonly used model-rocket motors, which are smaller and typically use a weaker fuel, do not require permits and will not be affected.
"The Safe Explosives Act has not, does not and will not affect that exemption," said Gail Davis, chief of the ATF's public safety branch.
Hobbyists also fear restrictions on how explosive material can be shipped will hamper businesses that make and sell rocket motors.
Curtailed shipping could lead to a de facto ban on motor sales, said Gregory Lyzenga, a model-rocket enthusiast and geophysics researcher at NASA's Jet Propulsion Laboratory.
"It's not as though there's been a law passed saying 'model rocketry is illegal,' but it's just that the materials are unavailable," Lyzenga said.
Rocketeers are suing ATF in federal court in Washington to force it to change its classification of APCP as an explosive. They say APCP burns and does not blow up. A decision is pending.
"The gasoline in the tank of your car would make a better bomb," Lyzenga said. "If I was looking for what I thought was a serious danger to public safety, I certainly would not start here."