Mark VIMark VIThe success of the MkV made me start to think a bout the bigger tubes I had stacked in the corner. If I could cluster four engines, why not six? Why not use D engines? I had a tube that would hold seven 24mm mounts, but it wasn't really long enough. So I decided to built a rocket reminiscent of the MkIV, with a transition, and forward fins. With the extra weight of the engines, the plywood fins and centering rings, this design turned out not to be stable ( Using RockSim). I increased the length of the upper tube ( forward of the transition) and removed the forward fins. That was a lot better.
I had heard of some larger black powder engines available in the UK form a company called Rocket Services and wanted to option of installing them. So I went for a removable cartridge system. The Fins werer mounted through the body wall and formed runners onto which the engine cartridge would slide. The cartridge was made up from two discs of plywood drilled with holes for the engine mounts. The cartridge slid in to the body on the runners and was then locked into position by rotating the whole thing. In the end I just went with six engines. Thrust rings were made from sawn up spent D engines and epoxied in to place. A stuffer tube was placed inside the main body, monted on two centering rings. At ignition the upper body was to seperate, each half with it's own parachute. Karen made a red and white hemispherical 'chute for the lower half, and I was going to use the pink circular 'chute for the upper half. We intended to fly it at the International Rocket Weekend, and I had a lot of help from Brain who made and painted the transition just days before we went.
At the event, a lot of doubt was raised about the engine cartridge system. 'Six D ejection charges will blow it out' they said. I also couldn't determine how I was going to ensure that both parachutes deployed. In the end I bought some big shock cord and tied both halves together on the red & white 'chute. Another hitch, I had planned to add another set of clips to my ignition system, but had forgotten ( that last week was hectic as I my work had taken me away from home for several days), and I didn't have a large enough launch pad...
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Luckily I learned of a new technique for clustering. This involves using a single igniter to ignite 'quick match' fuses that are fed into the individal engines. On of the organisers, John Bonsor, showed me how to do this. I managed to borrow a launcher and after a wait for the wind to die down, we were ready. The ignition and initial flight were perfect, except, what was that? A small object apperade to fly from the back at ejection, and wherer was the 'chute. The rocket came in balistically. What had happened was exactly what the 'doom sayers' were predicting. Even though I had staggered the ejection by using a mixture of D12 delays, the ejection gases pushed the engine cartridge out of the rear, instead of deploying the chute. The rocket was a write off. The engine cartridge shattered, the forward tube like a concertina, and the aft tube a slowly unwinding spiral.
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The pic of lift off was the last shout from my last roll of film, so mercifully there are no pictures of the rocket as we found it. The realisation of the hours we had all spent on this rocket, which was now trash, didn't sink in until later, and it was a long drive home from Largs to Leeds.
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