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How did I get involved in amateur rocketry? - Days of the LRG
Back in the days of 1981 I started doing experiments with rockets, being inspired by the Space Shuttle launch and by the Tom Wolfe book "The Right Stuff".
Without any previous knowledge, I started doing experiments using whatever nasty powders I could retrieve from left over fireworks. I didn't know then, but working with unknown pyrotechnic powders can be dangerous even for the type of small scale work I was doing. Small scale it was: the first rocket I made was 2 centimeters long and 5 millimeters in diameter. It sucessfully flew to an impressive altitude of approximately 80 centimeters, although it suffered from a nozzle burn through. Success at first attempt - but it was to be a while until it happened again.
After a while, I teamed up with a couple of other boys from the neigbourhood - Carsten and Morten - forming the LRG - Lyngby Raketgruppe wich was active in the years of 1982-1984. We searched the local library for any rocketry relevant litterature and came across the "Handbook of Model Rocketry" by G. Harry Stine. This was a giant leap forward and formed the conceptual basis for our work. We started dividing the rockets into airframes and motors. The handbook told us everything about airframe design and stabillity, but very little about the motors, as theese were supposed to be factory made.... We made our own "model rocket motors" with homemade gunpowder as propellant. This was a very specific no-no according to G. Harry Stine - so we did not qualify as model rocketeers. Anyway, the motors in question were quite small, only some 5 grams of propellant.  Examples of LRG's work: Airframes (with balsa wood nosecones), motors, motor supports and even ignition wires
The materials we used for theese rockets was mainly paper and glue. Even for the motors, no metal parts were used. In the beginning, we had a hard time doing a casing that would endure the maximum working pressure of the motor. The grains were wet pressed into a "semi-coreburner", thus they would generate a rapidly progressive thrust, followed by a period of constant thrust at a lower level. Typical burn times were in the range of 1.5 second.  Spectacular CATO
Eventually, reliabillity of the motors improved by redesigning the casing (primarely the top closure) and by static tests. No recordings of thrust were done - reliabillity was the prime concern. Means for doing thrust measurements were considered, and work was begun on an electronic loadcell based on the concept of a differential transformer - it was never completed though.
 The "Ugly dog" rocket.... I think I better skip the explanation....
Launches took place (mostly) on a pre WW1 fortress in the neigbourhood, now (and then) functioning as a recreational area. During day time only very few people visited the place, and we could do our stuff nearly undisturbed. Most launches were purely ballistic, as we did not master the delay and ejection charge technique that model rockets relied on. Instead we simply hoped that the nosecone would come off all by itself at the proper moment, releasing a toilet paper streamer. In practice, the nosecone did not separate - or it separated at the wrong moment, but quite often, theese very lightweight rockets survived anyway.  Nosecone separates at liftoff
Although the rockets were buildt and launched for fun, they gave valuable hands -on experience in the field of amateur rocketry. Experiments were done, flying rockets that were purposely made unstable. Even at this scale, the sight of an unstable rocket furiously spinning around was both impressive and scary. Theese experiments resulted in the creation of a simple stabillity test: The rocket was thrown in the air nose first and tail first. If it was flying straight in the nose first position and spinning around when thrown in the air in the tail first position, then it would be safe to fly.  A rocket, ready for flight, placed on a simple rod launcher - the rod was utilised from a defunct umbrella!
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