Before we can explore proper rocketry design and its application for our use, it is important that we understand the terms and regulatory considerations that apply to hobby rocketry. For example, what exactly is a “model rocket” versus a “high power” rocket? And, what about “amateur rockets”? This section answers these questions with verbiage taken from the R.M.R FAQ.
“Model”, “high power”, “advanced”, and “amateur” are all terms which have many definitions, depending to whom you are speaking. In the UseNET newsgroup rec.models.rockets., and in the Rocketry FAQ documents, the definitions (if any) accepted by the NFPA, National Association of Rocketry (NAR), and Tripoli Rocketry Association (TRA) are used. If these definitions conflict the NAR definition is used.
Model rockets are rockets that conform to the guidelines and restrictions defined in the NFPA 1122 document. These rockets weigh less than 1500 grams, contain less than 125 grams of total fuel, have no motor with more than 62.5 grams of fuel or more than 160 NS of total impulse, use only pre-manufactured, solid propellant motors, and do not use metal body tubes, nose cones or fins. One inconsistancy with this is the CPSC definition of a model rocket motor, which by their definition must contain no more than 80NS total impulse. NFPA document 1127-94 contains the most complete definition of a model rocket and the model rocket safety code. This is the same safety code as adopted by the NAR.
Large Model Rockets
Large Model Rockets is a term used in the FAA FAR 101 regulations. It refers to NAR/NFPA model rockets that are between 454 and 1500 grams (1 to 3.3 pounds) total liftoff weight and contain more than 113 grams but less than 125 grams of total fuel.
High Power Rockets
High power rockets are rockets that exceed the total weight, total propellant or single motor total impulse restrictions of model rockets, but otherwise conform to the same guidelines for construction materials and pre-manufactured, commericially made rocket motors. High power rockets also allow the use of metal structural components where such a material is necessary to insure structural integrity of the rocket. High power rockets have no total weight limits, but do have a single motor limit of no more than O power (40,960NS maximum total impulse) and have a total power limitation of 81,920NS total impulse. NFPA document 1127-1985 contains the most complete definition of a high power rocket and also the high power rocketry safety code. This safety code has been adopted by both the NAR and TRA. Metal bodied rockets are allowed by NFPA 1127 where metal is required to insure structural integrity of the rocket over all of its anticipated flight.
Amateur rockets covers all other non-professional rockets that do not meet the criteria for model or high power rockets. This includes metal bodied rockets, liquid or hybrid fueled rockets, and rockets with any type of homemade rocket motor.
Experimental rockets is an ambiguous term. In the early 1980s it was used to describe rockets that exceeded the model rocket limit at that time (1 pound total liftoff weight and no motor above F power). More recently, it has been used by the Tripoli Rocketry Association to describe the class of rockets that use pre-manufactured solid or hybrid rocket motors but that do not qualify as high power rockets. This includes metal bodied rockets and those with more than 80,000NS of total power.
HPR-lite is not any type of “official” rocket designation but has been used to refer to rockets that exceed the old NFPA model rocket limit of 1 pound but still qualify as NFPA model rocket under current guidelines. These rockets typically use E through G power and are built with much the same techniques as high power rockets. This term originated in the rec.models.rockets newsgroup. It should be noted that this term refers to legal model rockets, not any type of high power rocket, and might therefore be misleading to many. The term “Large Model Rocket” should be used instead.