Hobby rocketry consists of numerous propulsion techniques when it comes to motors. Early technology repeated the ancient Chinese’s use of firework-type propellents where later technology has investigated various methods of hybrid applications. The most wide-spread motors are the ones which make up the lower-powered model rockets and consist mainly of compressed black powder. When you get into mid and high power models, you see the overwhelming choice leaning toward composite-based motors, typically ammonium perchlorate, more commonly known as AP. There currently are several manufacturers of hybrid technology, which combines the use of inert materials while separate, but capable of controlled combustion when introduced to each other under the right circumstances. While they all rely on nitrous oxide as an oxidizer, you will se a variety of fuels, including plastic, ammonium perchlorate and paper.
The hobby of model rocketry saw its beginnings rooted in the development of pre-loaded rocket engines which didn’t require handling of chemicals by the fliers. These motors were mostly manufactured using black powder hydraulically compressed into spiral wound paper tubes. In the later part of the 1960’s, Irv Wait of Rocket Development Company introduced the world’s first composite model rocket motors using modern high energy propellant with a plastic binder called “EnerJets”. Later a subsidiary of Centuri Engineering Company, the EnerJets sold well until around 1974 when Centuri shut the production line down because of a variety of problems, from low profit margins to high manufacturing costs. Four years later, in 1978, Small Systems Sounding Rockets, later known as Crown Rocket Technology, and in 1979, Composite Dynamics, re-introduced the concept of high-energy composite model rocket motors. SSRS used a 1.125” diameter paper phenolic motor casings with machined graphite nozzles while Composite Dynamics utilized filament-wound fiberglass motor casings and cast ceramic nozzles. Both companies used HTPB (hydroxyl-terminated polybutadiene) fuel binder, at the time a breakthrough in model rocket motors. Composite Dynamics raised the state-of-the-art even further with its first motor, an E20. It had the same physical dimensions as an Estes D-12, yet it produced two and one half times as much power, a total of 40 newton-seconds. Since that time, other manufacturers have come on the scene to deliver today’s composite propellant motors, both in single use and reloadable motor technologies. This section explores the specifics of that technology.