This project is a really simple accelerometer based altimeter. The assembled board only weighs 10grams; the power supply is an additional 6grams. The data collection is done by a Basic Stamp II. It records 1 second before and 11 seconds after it detects the initial launch thrust. On their first launch they got some legitimate looking data (it would have been nice if they had an inclinometer to compare it to). The second launch resulted in a catastrophic engine failure on the pad. It’s a shame they couldn’t do more testing, but at least they’ve got video. Schematics and source code natch.
The photo above is from a recent BoingBoing post on high power rocketry.