Model rocket motors are classified by their impulse level. The more common black powder motors used by the Estes and Quest Aerospace kits and sold by the typical hobby shop are classified as low-power motors, typically A through D impulse. These are the rockets you will see folks launching at the park - where such an activity is legal, of course. I highly recommend that if you want to launch model rockets you do so only at sanctioned launches due to the inherent danger of a hobby which involves igniting highly energetic substances to propel objects into the air. Such launches will have multiple experts in attendance to provide direction and assistance, not to mention insurance coverage if something unfortunate does happen.
The next classification is mid-power and is usually associated with more complex rockets in terms of building materials, construction techniques, motor propellant, and performance. These are the E, F, and G impulse motors. Rather than black powder motors these are usually powered by Ammonium Perchlorate Composite Propellant (or APCP for short) although Estes does make a couple of BP motors that fall into this class. Estes makes a few kits of this nature in their Pro Series II rockets. Due to their power, performance, and danger factor it is best to save these powerful rockets for launch at a sanctioned club event where experienced model rocketeers are present. They can also fly high enough to require a waiver from the FAA, something most clubs will already have in place for model rocketry activities.
The last classification is high-power rocketry. Rockets in this class used motors of H or higher impulse and operate under a different set of regulations established by the National Fire Prevention Act (NFPA). To fly one of these rockets requires certification by either NAR or Tripoli. Within high-power rocketry there are also three different levels of certification, Level 1 (H and I impulse), Level 2 (J, K, and L impulse), and Level 3 (M impulse and beyond). The actual impulse levels are more specific, and some lower letter motors can actually have an impulse level that moves them into the next higher tier as far as certification level goes. These rockets can only be launched at events where there are specific provisions in place, such as an FAA altitude waiver. Rockets in this class can easily go many thousands of feet. Some are so powerful that they can even approach the edge of space! It is easy to see why they must only be launched under controlled conditions in suitable locations and with proper precautions in place!
Most of my rockets are Estes kits and fall into the low-power classification. However I do have two more powerful rockets. One of these rockets is an Aerotech IQSY Tomahawk and uses a 29mm motor mount. It can be flown with more powerful 24mm black powder and APCP motors using an adapter but is intended for use with 29mm APCP motors. It is a great performer and an exciting one to watch fly! Motors for this range from E impulse to the low I impulse range. Although designed as a mid-power rocket it can also fly on high-power motors with the appropriate certification.
The other is a K&S Super Flash. Sadly the company that made this kit is no longer in business. This rocket uses a 54mm tube, is 47.375 inches tall, and has a 38mm motor mount. This rocket is one I plan to use to get my Level 1 High-Power certification. I could also use it for Level 2 if I ever choose to certify at that level. Typical motors for this will range from G through J impulse levels. This rocket can reach altitudes from 2000 feet to well over 8000! It is designed as a dual deployment rocket although I plan to fly it in single-deployment mode for classification.
I haven't completely finished construction on this one yet but it is very close. Before I can fly it I have to decide which national organization to join and which of the many available H or I impulse motors to use. I'm fortunate in that I have a Tripoli prefecture that flies 20 minutes from my house where I can go to launch, as well as the largest of Southern California's NAR clubs about an hour away. Either one has members than can preside over a Level 1 certification flight.
Model rocketry is a fun and exciting hobby, and one that is a great family activity. By its nature it is extremely educational. Taking the time to learn the science behind the hobby is a huge part of the enjoyment!
