These kits require stronger construction methods and materials than typical model rockets. Another new trend is 'reloadable' motor technology. With reloadables you have a metal motor casing that you manually reload with solid fuel pellets, delay and ejection charge for each flight. The casing is reusable. The latest technology to hit the High Power rocket scene is the hybrid rocket motor.
Hybrid motors use components from both liquid and solid ful rocket motors.
Two companies have currently certified hybrid motors with Tripoli, Aerotech and Hypertek. The advantage of hybrid motors is that they use totally inert fuel grains, such as a cast polymer plastic or compressed paper pulp, which do not have any DOT or ATF restrictions. With both motors, nitrous oxide is used for the oxidizer. It used to be that one would see 30 or more people at an NAR regional, but today it sometimes seems like you are lucky if you get enough people to show up. Because I got back in to the hobby to fly competition, I am concerned about the apparent loss of interest in competition rocketry.