Avionics Avionics refers to any electronic systems flown on rockets, whether they be flight computers, guidance and control systems, telemetry systems or payloads. If there is space in a rocket, and it has sufficient thrust, then I believe strongly in filling it with some electronic systems and a useful sensor or two to either test engineering under operational conditions, or to carry out some scientific measurement. Nowadays, it is possible to fly miniature altimeters and accellerometers in all but the smallest rockets. The real fun though, is in designing and building your own avionics system for rocketry applications. Simple CPU's which can be used for onboard flight computers are the Z80, the 8031/8051 and the PIC 16xx, all are available for a cost of less than £10, and allow simple flight computer circuits to be built around them with relative ease. Personally, I would strongly recommend the PIC proccessor, since it is possible to construct some quite powerful systems around it, using less than 10 components. Avionics Power Systems The worst culprit when it comes to making the rocket too heavy to launch, is generally the power system (i.e. the batteries). Whilst the batteries used in radio controlled aircraft may look attractive for rocketry use, remember that radio controlled aircraft have wings, rockets don't. Important point this. Wings allow you to get away with a lot more, since they generate lift. Rockets are (usually) totally reliant on their thrust to stay airborne. With an aircraft or helicopter, if the motor stalls, then you can glide (most of the time). If the motor in a rocket stops prematurely, the rocket slows down and generally drops out of the sky. Thus every gram saved counts - this can mean compromises on the batteries, especially where the weight is really critical. There are a number of solutions to the power problem, most notably 12 Volt lighter batteries or PCB rechargeable batteries. The drawback to these type of batteries though is a very low power density, which means they run down quickly.