The 1990’s was a wonderful time to be a hobbyist.

The contagious optimism of that time lent itself well to the enthusiasms of people and families [ 😦  mostly men and mostly white] who bonded in far flung disciplines that had always been the purview of “trained professionals”.

One of the hobbies that decade “launched” was high power rocketry.  There were always two reactions the first time anyone ever saw a launch of anything bigger than the “Estes”rockets you could buy at any hobby store:  Awe and fear that you could do more than take someone’s eye out.  To assuage such fears, the hobby community itself, the US rocketsFederal Aviation Administration and the Bureau of Alcohol, Tobacco and Firearms provided strict regulations around the storage, purchase and use of any rocket motors with a specific impulse above 36 Lb-seconds.  In order to better assure that the hobbyist would align with these regulations, hobbyists associations coordinate the launches and supply amateurs with the supplies and training they need.

In 1996 I passed my level 1 certification and my level 2 in 1997.  In order to be certified to level 3 (allowing launch of rockets with a specific impulse exceeding 1,150 Lb-seconds) it was traditional to build something novel into the design.  In those days before cell phones and micro-power electronics the favorite was altimeter-based parachute deployment.

EricalchMine was a pic-based system with a clunky altimeter and an enormous T-1 accelerometer but what I really wanted to study was what’s called the mach disks of the rocket’s exhaust.  This is actually a phenomena that reveals volumes about the sonics, plasma and nozzles of all jet and rocket propulsion.