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:
"Traditional" Model Rocketry
As children, many of us launched model rockets. Today, Estes, Quest and several other manufacturers make these rockets. Estes and Quest model rockets are available in many hobby shops, and Estes rockets are commonly sold in Walmart stores. 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; for example a ‘C’ motor is up to twice as powerful as a ‘B’ motor. Composite propellant single-use and reloadable model rocket motors of ‘D’ size are also available from AeroTech. These rockets usually weigh less than a pound and fly to limited altitudes, which allows them to be flown in many open spaces without special permission or licenses. Model rockets are usually simple to build and are quite safe. Model rocket motors are relatively inexpensive, costing only a few dollars apiece.
Mid-Power Model Rocketry
Beyond "traditional" model rocketry is what many call "mid-power rocketry". Rockets in this category typically use composite propellant model rocket motors in the `E` through `G` sizes, although black powder `E` model rocket motors are also available. The largest manufacturer of mid-power model rocket kits and motors is AeroTech. Mid-power model rockets generally weigh less than two pounds, but can fly higher than traditional model rockets. Mid-power model rockets containing no more than 4.4 ounces (125 grams) of propellant and weighing no more than 3.3 pounds (1500 grams) may also be flown without special permission or licenses. Mid-power model rockets are not necessarily more difficult to build than traditional model rockets. Composite propellant mid-power model rocket motors are more expensive than the smaller black powder model rocket motors ($5-$27 per flight), but usually cost less per unit of power. Mid-power model rocket motors are produced in both single-use and reloadable types.
The largest rockets built with commercially manufactured motors and sanctioned by national organizations are classified as "High-Power Rockets". Rocket motors used in this class range from `H` through `O` in size and are almost always the reloadable type. The largest manufacturers of high-power kits are LOC/Precision and Public Missiles, Ltd., although there are several 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. High-power rocket motors require national user group (National Association of Rocketry or Tripoli Rocketry Association) certification to purchase and fly and can only be flown at organized club launches held in unpopulated areas of large open space with Federal Aviation Administration (FAA) clearances. High-power rockets are the most challenging rockets which fly on commercially-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.
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 larger high-power range. FAA requirements are the same as for high-power rocketry. Making your own motors can be dangerous and should not be undertaken lightly. Experimental 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.