Non-Professional Rocketry Categories
"Non-professional rocketry" is a very broad term used to define those involved in “hobby rocketry.” There are four basic categories in hobby or non-professional rocketry:

Model Rocketry
As children, many of us launched model rockets. Today, these rockets are made by Estes and Quest. Estes and Quest rockets are available in most hobby shops. These rockets use black powder motors up to "D" (20 N-sec) size. Each succeeding letter denotes up to twice the impulse of the smaller letter; a “C” motor is up to twice as powerful as a “B” motor. These rockets usually weigh a few ounces and fly less than 2000 feet high, which allows them to be flown in any open space without special permission. Model rockets are usually simple to build and are quite safe. Motors are relatively cheap, costing only a few dollars apiece.

Mid-Power Rocketry
Beyond model rocketry is what many call “mid-power rocketry.” Rockets in this category typically use composite propellant motors in the "E" through "G" sizes. The largest manufacturer of mid-power kits and motors is AeroTech. Mid-power rockets also generally weigh under a pound, but can fly much higher than model rockets. Rockets which contain over 4 ounces of propellant or weigh over 1 pound require Federal Aviation Administration (FAA) notification 24 to 48 hours in advance. Mid-power rockets are not necessarily more difficult to build than model rockets. Composite propellant rocket motors are more expensive than black powder motors ($4-$15 per flight), but usually less per unit of power.

High-Power Rocketry
The largest rockets built with commercially manufactured motors and sanctioned by national organizations are classified as “High-Power Rockets.” Motors used in this class range from "H" through "O" in size. The largest manufacturers of high-power kits are LOC/Precision and Public Missiles, Ltd., although there are other companies making these kits. These rockets generally weigh from a few pounds up to a hundred pounds or more and can fly up to 25,000 feet high or more. Some high-power rocket motors currently require federal licensing and approvals to purchase and fly and can only be flown at organized club launches held in unpopulated areas of large open space. High-power rockets are the most challenging rockets which fly on pre-manufactured motors and appeal to those who like large vehicles and enjoy the impressive flights with the larger, more powerful and more expensive ($20-$1,000 per flight) motors. More advanced materials and techniques are required for high-power rockets because of the dramatically increased stresses encountered in flight.

Experimental Rocketry
Those who build their own rocket motors rather than using commercially manufactured motors engage in a hobby rocket category known as “Experimental Rocketry.” Motors can be any size, though generally they tend to be in the smaller high-power range. In some ways, amateur rocketry is less regulated than high-power rocketry, although the FAA requirements are the same. Making your own motors can be dangerous and should not be undertaken lightly. Amateur rocketry is appealing to people who either want to do everything themselves or enjoy the process of developing and making their own motors. It should be noted, however, that making your own motors is rarely a money-saving proposition.