The Model Rocket design, the base for all the rockets I build (which will be dealt with in some later post) is employed here too while constructing a recovery-mechanism enabled, single-stage rocket; colloquially called the ‘parachute-rocket’. In subsequent posts I share my experiences, methods and all other details of the work done in preparing one component of the parachute-rocket.Developing this component is time consuming and demands ingenuity.This component is fragile yet a very important part of the recovery mechanism. It is aptly named the ‘Delay Charge’.
This post deals with the elementary meaning of the words ‘delay charge’, the biases held by me before beginning the experiments, the reason for these, the testing methods employed and their utility.
My work on developing a delay charge was very well done under the guidance of an experienced teacher. My methods were biased because I had my teacher’s experiences in designing the delay charge handy, which allowed me to develop over his earlier model, build new ones which were yet untested and abandon the methods which he found (through earlier experiments) as yet unyielding.
A brief explanation of what I mean by a delay charge follows. The Delay Charge is a device which comes into action after burnout. It catches fire from the extreme end of the engine at burnout and burns at a relatively slower pace compared to the engine. It burns slowly through the coasting phase and burns away completely sometime in the descent phase. It transfers its fire to the blasting material/device in the descent phase. The blasting device catches fire from the delay charge, blasts and causes the parachute to be pushed out of the body tube, in effect pushing out the nose cone. This is the mechanism of parachute deployment (to be clear, the deployment mechanism which I have tested and employed as of now). It is very clear how important a role does the delay charge play. The delay charge I have tested is largely a chemical device made up of a certain chemical composition which does not catch fire very readily yet burns completely. One can say that it needs a relatively higher temperature than the propellant to change its chemical properties and to burn in consequence.
While developing the delay charge my choices were biased not only because of the earlier experiences of my teacher but also due to, and based on the availability of resources. Naturally, the very need to develop a delay charge is due to the absence of model rocketry equipment manufacturing companies in the country. This was actually helpful in letting me build the delay charge as I wished right from the elementary components and to modify it as I desired. It is obvious that my testing methods were brute-force ‘trial-and-error’ methods. Simulating the internal mechanism of the delay charge beforehand using numerical techniques and computer-aided visualization is not helpful but instead time-consuming and irrelevant in the field of basic model rocketry; therefore such methods were neglected and direct prototype development was exercised.
Testing the prototype was done by supplying heat to it and recording the time taken for the fire to travel from one end to the other relative to the length of the delay charge. Due to the crude nature of the work done in basic model rocketry, any prototype which lasted for a time greater than the bare minimum of 2 seconds and less than the excessive of 10 seconds, for a given standard length of the delay charge was considered apt.
This was the basic background needed before describing the experiments conducted. The next post shall describe the conducted experiments in detail, the results obtained, and the conclusions made.