Report

Dordrecht, 7 Oktober, 2007 - Leon Krancher and Mark Uitendaal had prepared a new motor for their next rocket. This motor is of course bigger than the last and falls in the L-range. The test took again place at the club house of the Scouting club "Van Speijk".

After all preparations were done, the test started very well. But when the motor's propulsion was about used, there was a loud bang and a lot of smoke. Some spectators thought they had seen the motor in the air for a split second. Curious as we were, after some safety time, we went looking to discover what had happened. We found the motor lying in the grass next to the test stand, as well as the remains of some of the grains.

It appears the glass fibre reinforced plastic casing was not strong enough. Later, while studying the thrust curve, it was discovered the thrust was already reducing when the motor launched itself. So the casing failed just short of its useful life. In the previous test, which was a smaller motor, the metal nozzle had already melted the plastic casing a bit. Frames taken from a video shows the motor going up and down in eight frames, which is in about 0.3 seconds. The video also shows that the motor was launched almost vertically, which is not extraordinary as the motor rests in a hollow tube while testing. This hollow tube thus functioned as a mortar.

Leon Krancher and Mark Uitendaal also tested a parachute system, whereby a canister containing the parachute is launched with some black powder out of the rocket body by separating two tubes. During this test the canister was placed in a small piece of tube of similar diameter as the proposed rocket. This test tube was positioned at a low angle. The first test was not successful, as the canister was not blown out of its test tube. Only a small puff of smoke could be seen. The second test was successful and the canister was shot a few meters away from its test tube. This was followed by a third test, which was again unsuccessful. It even did not produce a small puff of smoke like the first test.