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, the AVR 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.
The Altimeter Fixation
Whenever people decide to build rocketry avionics, it is almost always an altimeter, and frequently they seem to think they can do it better or cheaper than the altimeters already on the market. Nothing wrong here, but when there are already 32 rocketry altimeters on the market, some with very sophisticated add-ons and very accurate sampling, I just don't see why people feel the need to re-invent the wheel.
If the same amount of effort was put into developing other avionics systems for rockets, it would broaden the options and provide yet more sophisticated avionics for rocketry. The rocketry market is crying out for more electronics along the lines of:
- Onboard RF Tracking Beacons
- Onboard RF Telemetry Systems
- Onboard Miniature Audio and Optical Location Beacons
- Onboard Multi-channel Data Acqusition Systems
- Onboard GPS
- Onboard Inertial Navigation
- On-pad Vehicle Monitoring Systems
Why people need to build just another altimeter that does the same or less than other altimeters on the market beats me. I've always been of the mindset; build on what has gone before and see what new things can be developed rather than let's just do what everyone else does. Some people are developing some of the systems on the list above, as well as other systems - the problem is, there's not enough people doing this.
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.
A more recent solution to the power system mass issue is the use of Lithium Polymer (LiPo) rechargeable batteries. LiPo batteries are still at this point, quite expensive, however, as they become more popular, the price will no doubt, drop.
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